From fbb00b568bc93073452d2a0f9f06e7c33d16eece Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Wed, 19 Jun 2013 23:56:22 +0200 Subject: [PATCH 01/24] sched: Consolidate open coded preemptible() checks preempt_schedule() and preempt_schedule_context() open code their preemptability checks. Use the standard API instead for consolidation. Signed-off-by: Frederic Weisbecker Cc: Ingo Molnar Cc: Li Zhong Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Steven Rostedt Cc: Thomas Gleixner Cc: Borislav Petkov Cc: Alex Shi Cc: Paul Turner Cc: Mike Galbraith Cc: Vincent Guittot --- kernel/context_tracking.c | 3 +-- kernel/sched/core.c | 4 +--- 2 files changed, 2 insertions(+), 5 deletions(-) diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c index 383f8231e436..942835c12ae5 100644 --- a/kernel/context_tracking.c +++ b/kernel/context_tracking.c @@ -87,10 +87,9 @@ void user_enter(void) */ void __sched notrace preempt_schedule_context(void) { - struct thread_info *ti = current_thread_info(); enum ctx_state prev_ctx; - if (likely(ti->preempt_count || irqs_disabled())) + if (likely(!preemptible())) return; /* diff --git a/kernel/sched/core.c b/kernel/sched/core.c index b7c32cb7bfeb..3fb7acee7326 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2510,13 +2510,11 @@ void __sched schedule_preempt_disabled(void) */ asmlinkage void __sched notrace preempt_schedule(void) { - struct thread_info *ti = current_thread_info(); - /* * If there is a non-zero preempt_count or interrupts are disabled, * we do not want to preempt the current task. Just return.. */ - if (likely(ti->preempt_count || irqs_disabled())) + if (likely(!preemptible())) return; do { From 2d854e5738cded368a0759f85b1197f5c044513d Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Fri, 12 Jul 2013 19:02:30 +0200 Subject: [PATCH 02/24] context_tracing: Fix guest accounting with native vtime 1) If context tracking is enabled with native vtime accounting (which combo is useless except for dev testing), we call vtime_guest_enter() and vtime_guest_exit() on host <-> guest switches. But those are stubs in this configurations. As a result, cputime is not correctly flushed on kvm context switches. 2) If context tracking runs but is disabled on some CPUs, those CPUs end up calling __guest_enter/__guest_exit which in turn call vtime_account_system(). We don't want to call this because we run in tick based accounting for these CPUs. Refactor the guest_enter/guest_exit code such that all combinations finally work. Signed-off-by: Frederic Weisbecker Cc: Steven Rostedt Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Li Zhong Cc: Mike Galbraith Cc: Kevin Hilman --- include/linux/context_tracking.h | 58 ++++++++++++++------------------ kernel/context_tracking.c | 6 ++-- 2 files changed, 29 insertions(+), 35 deletions(-) diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h index fc09d7b0dacf..5984f2556d13 100644 --- a/include/linux/context_tracking.h +++ b/include/linux/context_tracking.h @@ -20,25 +20,6 @@ struct context_tracking { } state; }; -static inline void __guest_enter(void) -{ - /* - * This is running in ioctl context so we can avoid - * the call to vtime_account() with its unnecessary idle check. - */ - vtime_account_system(current); - current->flags |= PF_VCPU; -} - -static inline void __guest_exit(void) -{ - /* - * This is running in ioctl context so we can avoid - * the call to vtime_account() with its unnecessary idle check. - */ - vtime_account_system(current); - current->flags &= ~PF_VCPU; -} #ifdef CONFIG_CONTEXT_TRACKING DECLARE_PER_CPU(struct context_tracking, context_tracking); @@ -56,9 +37,6 @@ static inline bool context_tracking_active(void) extern void user_enter(void); extern void user_exit(void); -extern void guest_enter(void); -extern void guest_exit(void); - static inline enum ctx_state exception_enter(void) { enum ctx_state prev_ctx; @@ -81,21 +59,35 @@ extern void context_tracking_task_switch(struct task_struct *prev, static inline bool context_tracking_in_user(void) { return false; } static inline void user_enter(void) { } static inline void user_exit(void) { } - -static inline void guest_enter(void) -{ - __guest_enter(); -} - -static inline void guest_exit(void) -{ - __guest_exit(); -} - static inline enum ctx_state exception_enter(void) { return 0; } static inline void exception_exit(enum ctx_state prev_ctx) { } static inline void context_tracking_task_switch(struct task_struct *prev, struct task_struct *next) { } #endif /* !CONFIG_CONTEXT_TRACKING */ +#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN +extern void guest_enter(void); +extern void guest_exit(void); +#else +static inline void guest_enter(void) +{ + /* + * This is running in ioctl context so we can avoid + * the call to vtime_account() with its unnecessary idle check. + */ + vtime_account_system(current); + current->flags |= PF_VCPU; +} + +static inline void guest_exit(void) +{ + /* + * This is running in ioctl context so we can avoid + * the call to vtime_account() with its unnecessary idle check. + */ + vtime_account_system(current); + current->flags &= ~PF_VCPU; +} +#endif /* CONFIG_VIRT_CPU_ACCOUNTING_GEN */ + #endif diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c index 942835c12ae5..1f47119c5b09 100644 --- a/kernel/context_tracking.c +++ b/kernel/context_tracking.c @@ -141,12 +141,13 @@ void user_exit(void) local_irq_restore(flags); } +#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN void guest_enter(void) { if (vtime_accounting_enabled()) vtime_guest_enter(current); else - __guest_enter(); + current->flags |= PF_VCPU; } EXPORT_SYMBOL_GPL(guest_enter); @@ -155,9 +156,10 @@ void guest_exit(void) if (vtime_accounting_enabled()) vtime_guest_exit(current); else - __guest_exit(); + current->flags &= ~PF_VCPU; } EXPORT_SYMBOL_GPL(guest_exit); +#endif /* CONFIG_VIRT_CPU_ACCOUNTING_GEN */ /** From 5b206d48e58204e84d249c4eb18651a1ff7a1274 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Fri, 12 Jul 2013 19:05:14 +0200 Subject: [PATCH 03/24] vtime: Update a few comments Update a stale comment from the old vtime era and document some locking that might be non obvious. Signed-off-by: Frederic Weisbecker Cc: Steven Rostedt Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Li Zhong Cc: Mike Galbraith Cc: Kevin Hilman --- include/linux/context_tracking.h | 10 ++++------ kernel/sched/cputime.c | 7 +++++++ 2 files changed, 11 insertions(+), 6 deletions(-) diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h index 5984f2556d13..d883ff0dd8fc 100644 --- a/include/linux/context_tracking.h +++ b/include/linux/context_tracking.h @@ -72,8 +72,9 @@ extern void guest_exit(void); static inline void guest_enter(void) { /* - * This is running in ioctl context so we can avoid - * the call to vtime_account() with its unnecessary idle check. + * This is running in ioctl context so its safe + * to assume that it's the stime pending cputime + * to flush. */ vtime_account_system(current); current->flags |= PF_VCPU; @@ -81,10 +82,7 @@ static inline void guest_enter(void) static inline void guest_exit(void) { - /* - * This is running in ioctl context so we can avoid - * the call to vtime_account() with its unnecessary idle check. - */ + /* Flush the guest cputime we spent on the guest */ vtime_account_system(current); current->flags &= ~PF_VCPU; } diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c index a7959e05a9d5..223a35efa0a6 100644 --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -712,6 +712,13 @@ void vtime_user_enter(struct task_struct *tsk) void vtime_guest_enter(struct task_struct *tsk) { + /* + * The flags must be updated under the lock with + * the vtime_snap flush and update. + * That enforces a right ordering and update sequence + * synchronization against the reader (task_gtime()) + * that can thus safely catch up with a tickless delta. + */ write_seqlock(&tsk->vtime_seqlock); __vtime_account_system(tsk); current->flags |= PF_VCPU; From d65ec12127a5b6c6d7f5331c78157dab98a20ff0 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Thu, 11 Jul 2013 23:59:33 +0200 Subject: [PATCH 04/24] context_tracking: Fix runtime CPU off-case As long as the context tracking is enabled on any CPU, even a single one, all other CPUs need to keep track of their user <-> kernel boundaries cross as well. This is because a task can sleep while servicing an exception that happened in the kernel or in userspace. Then when the task eventually wakes up and return from the exception, the CPU needs to know if we resume in userspace or in the kernel. exception_exit() get this information from exception_enter() that saved the previous state. If the CPU where the exception happened didn't keep track of these informations, exception_exit() doesn't know which state tracking to restore on the CPU where the task got migrated and we may return to userspace with the context tracking subsystem thinking that we are in kernel mode. This can be fixed in the long term if we move our context tracking probes on very low level arch fast path user <-> kernel boundary, although even that is worrisome as an exception can still happen in the few instructions between the probe and the actual iret. Also we are not yet ready to set these probes in the fast path given the potential overhead problem it induces. So let's fix this by always enable context tracking even on CPUs that are not in the full dynticks range. OTOH we can spare the rcu_user_*() and vtime_user_*() calls there because the tick runs on these CPUs and we can handle RCU state machine and cputime accounting through it. Signed-off-by: Frederic Weisbecker Cc: Steven Rostedt Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Li Zhong Cc: Mike Galbraith Cc: Kevin Hilman --- kernel/context_tracking.c | 52 +++++++++++++++++++++++++-------------- 1 file changed, 33 insertions(+), 19 deletions(-) diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c index 1f47119c5b09..7b095de356c5 100644 --- a/kernel/context_tracking.c +++ b/kernel/context_tracking.c @@ -54,17 +54,31 @@ void user_enter(void) WARN_ON_ONCE(!current->mm); local_irq_save(flags); - if (__this_cpu_read(context_tracking.active) && - __this_cpu_read(context_tracking.state) != IN_USER) { + if ( __this_cpu_read(context_tracking.state) != IN_USER) { + if (__this_cpu_read(context_tracking.active)) { + /* + * At this stage, only low level arch entry code remains and + * then we'll run in userspace. We can assume there won't be + * any RCU read-side critical section until the next call to + * user_exit() or rcu_irq_enter(). Let's remove RCU's dependency + * on the tick. + */ + vtime_user_enter(current); + rcu_user_enter(); + } /* - * At this stage, only low level arch entry code remains and - * then we'll run in userspace. We can assume there won't be - * any RCU read-side critical section until the next call to - * user_exit() or rcu_irq_enter(). Let's remove RCU's dependency - * on the tick. + * Even if context tracking is disabled on this CPU, because it's outside + * the full dynticks mask for example, we still have to keep track of the + * context transitions and states to prevent inconsistency on those of + * other CPUs. + * If a task triggers an exception in userspace, sleep on the exception + * handler and then migrate to another CPU, that new CPU must know where + * the exception returns by the time we call exception_exit(). + * This information can only be provided by the previous CPU when it called + * exception_enter(). + * OTOH we can spare the calls to vtime and RCU when context_tracking.active + * is false because we know that CPU is not tickless. */ - vtime_user_enter(current); - rcu_user_enter(); __this_cpu_write(context_tracking.state, IN_USER); } local_irq_restore(flags); @@ -130,12 +144,14 @@ void user_exit(void) local_irq_save(flags); if (__this_cpu_read(context_tracking.state) == IN_USER) { - /* - * We are going to run code that may use RCU. Inform - * RCU core about that (ie: we may need the tick again). - */ - rcu_user_exit(); - vtime_user_exit(current); + if (__this_cpu_read(context_tracking.active)) { + /* + * We are going to run code that may use RCU. Inform + * RCU core about that (ie: we may need the tick again). + */ + rcu_user_exit(); + vtime_user_exit(current); + } __this_cpu_write(context_tracking.state, IN_KERNEL); } local_irq_restore(flags); @@ -178,8 +194,6 @@ EXPORT_SYMBOL_GPL(guest_exit); void context_tracking_task_switch(struct task_struct *prev, struct task_struct *next) { - if (__this_cpu_read(context_tracking.active)) { - clear_tsk_thread_flag(prev, TIF_NOHZ); - set_tsk_thread_flag(next, TIF_NOHZ); - } + clear_tsk_thread_flag(prev, TIF_NOHZ); + set_tsk_thread_flag(next, TIF_NOHZ); } From 2e70933866ace52091a3c11a5c104c063ab0c445 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Wed, 10 Jul 2013 00:55:25 +0200 Subject: [PATCH 05/24] nohz: Only enable context tracking on full dynticks CPUs The context tracking subsystem has the ability to selectively enable the tracking on any defined subset of CPU. This means that we can define a CPU range that doesn't run the context tracking and another range that does. Now what we want in practice is to enable the tracking on full dynticks CPUs only. In order to perform this, we just need to pass our full dynticks CPU range selection from the full dynticks subsystem to the context tracking. This way we can spare the overhead of RCU user extended quiescent state and vtime maintainance on the CPUs that are outside the full dynticks range. Just keep in mind the raw context tracking itself is still necessary everywhere. Signed-off-by: Frederic Weisbecker Cc: Steven Rostedt Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Li Zhong Cc: Mike Galbraith Cc: Kevin Hilman --- include/linux/context_tracking.h | 2 ++ kernel/context_tracking.c | 5 +++++ kernel/time/tick-sched.c | 6 ++++++ 3 files changed, 13 insertions(+) diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h index d883ff0dd8fc..1ae37c708c63 100644 --- a/include/linux/context_tracking.h +++ b/include/linux/context_tracking.h @@ -34,6 +34,8 @@ static inline bool context_tracking_active(void) return __this_cpu_read(context_tracking.active); } +extern void context_tracking_cpu_set(int cpu); + extern void user_enter(void); extern void user_exit(void); diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c index 7b095de356c5..72bcb2570d3e 100644 --- a/kernel/context_tracking.c +++ b/kernel/context_tracking.c @@ -26,6 +26,11 @@ DEFINE_PER_CPU(struct context_tracking, context_tracking) = { #endif }; +void context_tracking_cpu_set(int cpu) +{ + per_cpu(context_tracking.active, cpu) = true; +} + /** * user_enter - Inform the context tracking that the CPU is going to * enter userspace mode. diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 9563c744dad2..91a2528b5f44 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -23,6 +23,7 @@ #include #include #include +#include #include @@ -344,11 +345,16 @@ static int tick_nohz_init_all(void) void __init tick_nohz_init(void) { + int cpu; + if (!have_nohz_full_mask) { if (tick_nohz_init_all() < 0) return; } + for_each_cpu(cpu, nohz_full_mask) + context_tracking_cpu_set(cpu); + cpu_notifier(tick_nohz_cpu_down_callback, 0); cpulist_scnprintf(nohz_full_buf, sizeof(nohz_full_buf), nohz_full_mask); pr_info("NO_HZ: Full dynticks CPUs: %s.\n", nohz_full_buf); From d84d27a491880b9902b45c09be8d9e9464fb9b74 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Wed, 24 Jul 2013 21:59:29 +0200 Subject: [PATCH 06/24] context_tracking: Remove full dynticks' hacky dependency on wide context tracking Now that the full dynticks subsystem only enables the context tracking on full dynticks CPUs, lets remove the dependency on CONTEXT_TRACKING_FORCE This dependency was a hack to enable the context tracking widely for the full dynticks susbsystem until the latter becomes able to enable it in a more CPU-finegrained fashion. Now CONTEXT_TRACKING_FORCE only stands for testing on archs that work on support for the context tracking while full dynticks can't be used yet due to unmet dependencies. It simulates a system where all CPUs are full dynticks so that RCU user extended quiescent states and dynticks cputime accounting can be tested on the given arch. Signed-off-by: Frederic Weisbecker Cc: Steven Rostedt Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Li Zhong Cc: Mike Galbraith Cc: Kevin Hilman --- init/Kconfig | 28 ++++++++++++++++++++++------ kernel/time/Kconfig | 1 - 2 files changed, 22 insertions(+), 7 deletions(-) diff --git a/init/Kconfig b/init/Kconfig index 247084be0590..ffbf5d788bf3 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -527,13 +527,29 @@ config RCU_USER_QS config CONTEXT_TRACKING_FORCE bool "Force context tracking" depends on CONTEXT_TRACKING - default CONTEXT_TRACKING + default y if !NO_HZ_FULL help - Probe on user/kernel boundaries by default in order to - test the features that rely on it such as userspace RCU extended - quiescent states. - This test is there for debugging until we have a real user like the - full dynticks mode. + The major pre-requirement for full dynticks to work is to + support the context tracking subsystem. But there are also + other dependencies to provide in order to make the full + dynticks working. + + This option stands for testing when an arch implements the + context tracking backend but doesn't yet fullfill all the + requirements to make the full dynticks feature working. + Without the full dynticks, there is no way to test the support + for context tracking and the subsystems that rely on it: RCU + userspace extended quiescent state and tickless cputime + accounting. This option copes with the absence of the full + dynticks subsystem by forcing the context tracking on all + CPUs in the system. + + Say Y only if you're working on the developpement of an + architecture backend for the context tracking. + + Say N otherwise, this option brings an overhead that you + don't want in production. + config RCU_FANOUT int "Tree-based hierarchical RCU fanout value" diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig index 70f27e89012b..747bbc70f53b 100644 --- a/kernel/time/Kconfig +++ b/kernel/time/Kconfig @@ -105,7 +105,6 @@ config NO_HZ_FULL select RCU_USER_QS select RCU_NOCB_CPU select VIRT_CPU_ACCOUNTING_GEN - select CONTEXT_TRACKING_FORCE select IRQ_WORK help Adaptively try to shutdown the tick whenever possible, even when From 65f382fd0c8fa483713c0971de9f1dfb4cf1ad9c Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Thu, 11 Jul 2013 19:12:32 +0200 Subject: [PATCH 07/24] context_tracking: Ground setup for static key use Prepare for using a static key in the context tracking subsystem. This will help optimizing the off case on its many users: * user_enter, user_exit, exception_enter, exception_exit, guest_enter, guest_exit, vtime_*() Signed-off-by: Frederic Weisbecker Cc: Steven Rostedt Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Li Zhong Cc: Mike Galbraith Cc: Kevin Hilman --- include/linux/context_tracking.h | 10 ++++++++++ init/main.c | 2 ++ kernel/context_tracking.c | 23 +++++++++++++++++------ 3 files changed, 29 insertions(+), 6 deletions(-) diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h index 1ae37c708c63..c138c24bad1a 100644 --- a/include/linux/context_tracking.h +++ b/include/linux/context_tracking.h @@ -4,6 +4,7 @@ #include #include #include +#include #include struct context_tracking { @@ -22,6 +23,7 @@ struct context_tracking { #ifdef CONFIG_CONTEXT_TRACKING +extern struct static_key context_tracking_enabled; DECLARE_PER_CPU(struct context_tracking, context_tracking); static inline bool context_tracking_in_user(void) @@ -67,6 +69,14 @@ static inline void context_tracking_task_switch(struct task_struct *prev, struct task_struct *next) { } #endif /* !CONFIG_CONTEXT_TRACKING */ + +#ifdef CONFIG_CONTEXT_TRACKING_FORCE +extern void context_tracking_init(void); +#else +static inline void context_tracking_init(void) { } +#endif /* CONFIG_CONTEXT_TRACKING_FORCE */ + + #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN extern void guest_enter(void); extern void guest_exit(void); diff --git a/init/main.c b/init/main.c index d03d2ec2eacf..af310afbef28 100644 --- a/init/main.c +++ b/init/main.c @@ -75,6 +75,7 @@ #include #include #include +#include #include #include @@ -545,6 +546,7 @@ asmlinkage void __init start_kernel(void) idr_init_cache(); rcu_init(); tick_nohz_init(); + context_tracking_init(); radix_tree_init(); /* init some links before init_ISA_irqs() */ early_irq_init(); diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c index 72bcb2570d3e..839d377d0da5 100644 --- a/kernel/context_tracking.c +++ b/kernel/context_tracking.c @@ -20,15 +20,16 @@ #include #include -DEFINE_PER_CPU(struct context_tracking, context_tracking) = { -#ifdef CONFIG_CONTEXT_TRACKING_FORCE - .active = true, -#endif -}; +struct static_key context_tracking_enabled = STATIC_KEY_INIT_FALSE; + +DEFINE_PER_CPU(struct context_tracking, context_tracking); void context_tracking_cpu_set(int cpu) { - per_cpu(context_tracking.active, cpu) = true; + if (!per_cpu(context_tracking.active, cpu)) { + per_cpu(context_tracking.active, cpu) = true; + static_key_slow_inc(&context_tracking_enabled); + } } /** @@ -202,3 +203,13 @@ void context_tracking_task_switch(struct task_struct *prev, clear_tsk_thread_flag(prev, TIF_NOHZ); set_tsk_thread_flag(next, TIF_NOHZ); } + +#ifdef CONFIG_CONTEXT_TRACKING_FORCE +void __init context_tracking_init(void) +{ + int cpu; + + for_each_possible_cpu(cpu) + context_tracking_cpu_set(cpu); +} +#endif From ad65782fba507d91a0a98f519b59e79cac1b474c Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Wed, 10 Jul 2013 02:44:35 +0200 Subject: [PATCH 08/24] context_tracking: Optimize main APIs off case with static key Optimize user and exception entry/exit APIs with static keys. This minimize the overhead for those who enable CONFIG_NO_HZ_FULL without always using it. Having no range passed to nohz_full= should result in the probes to be nopped (at least we hope so...). If this proves not be enough in the long term, we'll need to bring an exception slow path by re-routing the exception handlers. Signed-off-by: Frederic Weisbecker Cc: Steven Rostedt Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Li Zhong Cc: Mike Galbraith Cc: Kevin Hilman --- include/linux/context_tracking.h | 27 ++++++++++++++++++++++----- kernel/context_tracking.c | 12 ++++++------ 2 files changed, 28 insertions(+), 11 deletions(-) diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h index c138c24bad1a..38ab60b3f3a6 100644 --- a/include/linux/context_tracking.h +++ b/include/linux/context_tracking.h @@ -38,23 +38,40 @@ static inline bool context_tracking_active(void) extern void context_tracking_cpu_set(int cpu); -extern void user_enter(void); -extern void user_exit(void); +extern void context_tracking_user_enter(void); +extern void context_tracking_user_exit(void); + +static inline void user_enter(void) +{ + if (static_key_false(&context_tracking_enabled)) + context_tracking_user_enter(); + +} +static inline void user_exit(void) +{ + if (static_key_false(&context_tracking_enabled)) + context_tracking_user_exit(); +} static inline enum ctx_state exception_enter(void) { enum ctx_state prev_ctx; + if (!static_key_false(&context_tracking_enabled)) + return 0; + prev_ctx = this_cpu_read(context_tracking.state); - user_exit(); + context_tracking_user_exit(); return prev_ctx; } static inline void exception_exit(enum ctx_state prev_ctx) { - if (prev_ctx == IN_USER) - user_enter(); + if (static_key_false(&context_tracking_enabled)) { + if (prev_ctx == IN_USER) + context_tracking_user_enter(); + } } extern void context_tracking_task_switch(struct task_struct *prev, diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c index 839d377d0da5..6e89e094c80e 100644 --- a/kernel/context_tracking.c +++ b/kernel/context_tracking.c @@ -33,15 +33,15 @@ void context_tracking_cpu_set(int cpu) } /** - * user_enter - Inform the context tracking that the CPU is going to - * enter userspace mode. + * context_tracking_user_enter - Inform the context tracking that the CPU is going to + * enter userspace mode. * * This function must be called right before we switch from the kernel * to userspace, when it's guaranteed the remaining kernel instructions * to execute won't use any RCU read side critical section because this * function sets RCU in extended quiescent state. */ -void user_enter(void) +void context_tracking_user_enter(void) { unsigned long flags; @@ -131,8 +131,8 @@ EXPORT_SYMBOL_GPL(preempt_schedule_context); #endif /* CONFIG_PREEMPT */ /** - * user_exit - Inform the context tracking that the CPU is - * exiting userspace mode and entering the kernel. + * context_tracking_user_exit - Inform the context tracking that the CPU is + * exiting userspace mode and entering the kernel. * * This function must be called after we entered the kernel from userspace * before any use of RCU read side critical section. This potentially include @@ -141,7 +141,7 @@ EXPORT_SYMBOL_GPL(preempt_schedule_context); * This call supports re-entrancy. This way it can be called from any exception * handler without needing to know if we came from userspace or not. */ -void user_exit(void) +void context_tracking_user_exit(void) { unsigned long flags; From 48d6a816a8bf36e2a197c322697323003bdc1cfe Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Wed, 10 Jul 2013 02:44:35 +0200 Subject: [PATCH 09/24] context_tracking: Optimize guest APIs off case with static key Optimize guest entry/exit APIs with static keys. This minimize the overhead for those who enable CONFIG_NO_HZ_FULL without always using it. Having no range passed to nohz_full= should result in the probes overhead to be minimized. Signed-off-by: Frederic Weisbecker Cc: Steven Rostedt Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Li Zhong Cc: Mike Galbraith Cc: Kevin Hilman --- include/linux/context_tracking.h | 19 +++++++++++++++++-- kernel/context_tracking.c | 23 ++--------------------- kernel/sched/cputime.c | 2 ++ 3 files changed, 21 insertions(+), 23 deletions(-) diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h index 38ab60b3f3a6..8854eadb2142 100644 --- a/include/linux/context_tracking.h +++ b/include/linux/context_tracking.h @@ -95,8 +95,23 @@ static inline void context_tracking_init(void) { } #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN -extern void guest_enter(void); -extern void guest_exit(void); +static inline void guest_enter(void) +{ + if (static_key_false(&context_tracking_enabled) && + vtime_accounting_enabled()) + vtime_guest_enter(current); + else + current->flags |= PF_VCPU; +} + +static inline void guest_exit(void) +{ + if (static_key_false(&context_tracking_enabled) && + vtime_accounting_enabled()) + vtime_guest_exit(current); + else + current->flags &= ~PF_VCPU; +} #else static inline void guest_enter(void) { diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c index 6e89e094c80e..b6a186c4b886 100644 --- a/kernel/context_tracking.c +++ b/kernel/context_tracking.c @@ -21,8 +21,10 @@ #include struct static_key context_tracking_enabled = STATIC_KEY_INIT_FALSE; +EXPORT_SYMBOL_GPL(context_tracking_enabled); DEFINE_PER_CPU(struct context_tracking, context_tracking); +EXPORT_SYMBOL_GPL(context_tracking); void context_tracking_cpu_set(int cpu) { @@ -163,27 +165,6 @@ void context_tracking_user_exit(void) local_irq_restore(flags); } -#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN -void guest_enter(void) -{ - if (vtime_accounting_enabled()) - vtime_guest_enter(current); - else - current->flags |= PF_VCPU; -} -EXPORT_SYMBOL_GPL(guest_enter); - -void guest_exit(void) -{ - if (vtime_accounting_enabled()) - vtime_guest_exit(current); - else - current->flags &= ~PF_VCPU; -} -EXPORT_SYMBOL_GPL(guest_exit); -#endif /* CONFIG_VIRT_CPU_ACCOUNTING_GEN */ - - /** * context_tracking_task_switch - context switch the syscall callbacks * @prev: the task that is being switched out diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c index 223a35efa0a6..bb6b29a3067c 100644 --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -724,6 +724,7 @@ void vtime_guest_enter(struct task_struct *tsk) current->flags |= PF_VCPU; write_sequnlock(&tsk->vtime_seqlock); } +EXPORT_SYMBOL_GPL(vtime_guest_enter); void vtime_guest_exit(struct task_struct *tsk) { @@ -732,6 +733,7 @@ void vtime_guest_exit(struct task_struct *tsk) current->flags &= ~PF_VCPU; write_sequnlock(&tsk->vtime_seqlock); } +EXPORT_SYMBOL_GPL(vtime_guest_exit); void vtime_account_idle(struct task_struct *tsk) { From 73d424f9af7b571276e6284617cb59726d47bf12 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Thu, 11 Jul 2013 19:42:13 +0200 Subject: [PATCH 10/24] context_tracking: Optimize context switch off case with static keys No need for syscall slowpath if no CPU is full dynticks, rather nop this in this case. Signed-off-by: Frederic Weisbecker Cc: Steven Rostedt Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Li Zhong Cc: Mike Galbraith Cc: Kevin Hilman --- include/linux/context_tracking.h | 11 +++++++++-- kernel/context_tracking.c | 6 +++--- 2 files changed, 12 insertions(+), 5 deletions(-) diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h index 8854eadb2142..e070ea5dadac 100644 --- a/include/linux/context_tracking.h +++ b/include/linux/context_tracking.h @@ -40,6 +40,8 @@ extern void context_tracking_cpu_set(int cpu); extern void context_tracking_user_enter(void); extern void context_tracking_user_exit(void); +extern void __context_tracking_task_switch(struct task_struct *prev, + struct task_struct *next); static inline void user_enter(void) { @@ -74,8 +76,12 @@ static inline void exception_exit(enum ctx_state prev_ctx) } } -extern void context_tracking_task_switch(struct task_struct *prev, - struct task_struct *next); +static inline void context_tracking_task_switch(struct task_struct *prev, + struct task_struct *next) +{ + if (static_key_false(&context_tracking_enabled)) + __context_tracking_task_switch(prev, next); +} #else static inline bool context_tracking_in_user(void) { return false; } static inline void user_enter(void) { } @@ -112,6 +118,7 @@ static inline void guest_exit(void) else current->flags &= ~PF_VCPU; } + #else static inline void guest_enter(void) { diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c index b6a186c4b886..c17822673c39 100644 --- a/kernel/context_tracking.c +++ b/kernel/context_tracking.c @@ -166,7 +166,7 @@ void context_tracking_user_exit(void) } /** - * context_tracking_task_switch - context switch the syscall callbacks + * __context_tracking_task_switch - context switch the syscall callbacks * @prev: the task that is being switched out * @next: the task that is being switched in * @@ -178,8 +178,8 @@ void context_tracking_user_exit(void) * migrate to some CPU that doesn't do the context tracking. As such the TIF * flag may not be desired there. */ -void context_tracking_task_switch(struct task_struct *prev, - struct task_struct *next) +void __context_tracking_task_switch(struct task_struct *prev, + struct task_struct *next) { clear_tsk_thread_flag(prev, TIF_NOHZ); set_tsk_thread_flag(next, TIF_NOHZ); From 1b6a259aa5ab16d8b215bfc19ff7c9ffa8858f10 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Thu, 11 Jul 2013 20:27:43 +0200 Subject: [PATCH 11/24] context_tracking: User/kernel broundary cross trace events This can be useful to track all kernel/user round trips. And it's also helpful to debug the context tracking subsystem. Signed-off-by: Frederic Weisbecker Cc: Steven Rostedt Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Li Zhong Cc: Mike Galbraith Cc: Kevin Hilman --- include/trace/events/context_tracking.h | 58 +++++++++++++++++++++++++ kernel/context_tracking.c | 5 +++ 2 files changed, 63 insertions(+) create mode 100644 include/trace/events/context_tracking.h diff --git a/include/trace/events/context_tracking.h b/include/trace/events/context_tracking.h new file mode 100644 index 000000000000..ce8007cf29cf --- /dev/null +++ b/include/trace/events/context_tracking.h @@ -0,0 +1,58 @@ +#undef TRACE_SYSTEM +#define TRACE_SYSTEM context_tracking + +#if !defined(_TRACE_CONTEXT_TRACKING_H) || defined(TRACE_HEADER_MULTI_READ) +#define _TRACE_CONTEXT_TRACKING_H + +#include + +DECLARE_EVENT_CLASS(context_tracking_user, + + TP_PROTO(int dummy), + + TP_ARGS(dummy), + + TP_STRUCT__entry( + __field( int, dummy ) + ), + + TP_fast_assign( + __entry->dummy = dummy; + ), + + TP_printk("%s", "") +); + +/** + * user_enter - called when the kernel resumes to userspace + * @dummy: dummy arg to make trace event macro happy + * + * This event occurs when the kernel resumes to userspace after + * an exception or a syscall. + */ +DEFINE_EVENT(context_tracking_user, user_enter, + + TP_PROTO(int dummy), + + TP_ARGS(dummy) +); + +/** + * user_exit - called when userspace enters the kernel + * @dummy: dummy arg to make trace event macro happy + * + * This event occurs when userspace enters the kernel through + * an exception or a syscall. + */ +DEFINE_EVENT(context_tracking_user, user_exit, + + TP_PROTO(int dummy), + + TP_ARGS(dummy) +); + + +#endif /* _TRACE_CONTEXT_TRACKING_H */ + +/* This part must be outside protection */ +#include diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c index c17822673c39..247091bf0587 100644 --- a/kernel/context_tracking.c +++ b/kernel/context_tracking.c @@ -20,6 +20,9 @@ #include #include +#define CREATE_TRACE_POINTS +#include + struct static_key context_tracking_enabled = STATIC_KEY_INIT_FALSE; EXPORT_SYMBOL_GPL(context_tracking_enabled); @@ -64,6 +67,7 @@ void context_tracking_user_enter(void) local_irq_save(flags); if ( __this_cpu_read(context_tracking.state) != IN_USER) { if (__this_cpu_read(context_tracking.active)) { + trace_user_enter(0); /* * At this stage, only low level arch entry code remains and * then we'll run in userspace. We can assume there won't be @@ -159,6 +163,7 @@ void context_tracking_user_exit(void) */ rcu_user_exit(); vtime_user_exit(current); + trace_user_exit(0); } __this_cpu_write(context_tracking.state, IN_KERNEL); } From 7621d1f8bcb418e7a7ac583e89e38ec01b7ed182 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Sat, 13 Jul 2013 17:07:35 +0200 Subject: [PATCH 12/24] vtime: Remove a few unneeded generic vtime state checks Some generic vtime APIs check if the vtime accounting is enabled on the local CPU before doing their work. Some of these are not needed because all their callers already take care of that. Let's remove the checks on these. Signed-off-by: Frederic Weisbecker Cc: Steven Rostedt Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Li Zhong Cc: Mike Galbraith Cc: Kevin Hilman --- kernel/sched/cputime.c | 13 +------------ 1 file changed, 1 insertion(+), 12 deletions(-) diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c index bb6b29a3067c..5f273b477764 100644 --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -664,9 +664,6 @@ static void __vtime_account_system(struct task_struct *tsk) void vtime_account_system(struct task_struct *tsk) { - if (!vtime_accounting_enabled()) - return; - write_seqlock(&tsk->vtime_seqlock); __vtime_account_system(tsk); write_sequnlock(&tsk->vtime_seqlock); @@ -686,12 +683,7 @@ void vtime_account_irq_exit(struct task_struct *tsk) void vtime_account_user(struct task_struct *tsk) { - cputime_t delta_cpu; - - if (!vtime_accounting_enabled()) - return; - - delta_cpu = get_vtime_delta(tsk); + cputime_t delta_cpu = get_vtime_delta(tsk); write_seqlock(&tsk->vtime_seqlock); tsk->vtime_snap_whence = VTIME_SYS; @@ -701,9 +693,6 @@ void vtime_account_user(struct task_struct *tsk) void vtime_user_enter(struct task_struct *tsk) { - if (!vtime_accounting_enabled()) - return; - write_seqlock(&tsk->vtime_seqlock); tsk->vtime_snap_whence = VTIME_USER; __vtime_account_system(tsk); From 54461562c90e0ac104764c5a9de637fd9151a1c1 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Sat, 13 Jul 2013 17:10:18 +0200 Subject: [PATCH 13/24] vtime: Fix racy cputime delta update get_vtime_delta() must be called under the task vtime_seqlock with the code that does the cputime accounting flush. Otherwise the cputime reader can be fooled and run into a race where it sees the snapshot update but misses the cputime flush. As a result it can report a cputime that is way too short. Fix vtime_account_user() that wasn't complying to that rule. Signed-off-by: Frederic Weisbecker Cc: Steven Rostedt Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Li Zhong Cc: Mike Galbraith Cc: Kevin Hilman --- kernel/sched/cputime.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c index 5f273b477764..b62d5c027c7e 100644 --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -683,9 +683,10 @@ void vtime_account_irq_exit(struct task_struct *tsk) void vtime_account_user(struct task_struct *tsk) { - cputime_t delta_cpu = get_vtime_delta(tsk); + cputime_t delta_cpu; write_seqlock(&tsk->vtime_seqlock); + delta_cpu = get_vtime_delta(tsk); tsk->vtime_snap_whence = VTIME_SYS; account_user_time(tsk, delta_cpu, cputime_to_scaled(delta_cpu)); write_sequnlock(&tsk->vtime_seqlock); From e7358b3bc0d7fcec0e7a724477f06db2b0c68e21 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Fri, 12 Jul 2013 02:15:49 +0200 Subject: [PATCH 14/24] context_tracking: Split low level state headers We plan to use the context tracking static key on inline vtime APIs. For this we need to include the context tracking headers from those of vtime. However vtime headers need to stay low level because they are included in hardirq.h that mostly contains standalone definitions. But context_tracking.h includes sched.h for a few task_struct references, therefore it wouldn't be sensible to include it from vtime.h To solve this, lets split the context tracking headers and move out the pure state definitions that only require a few low level headers. We can safely include that small part in vtime.h later. Signed-off-by: Frederic Weisbecker Cc: Steven Rostedt Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Li Zhong Cc: Mike Galbraith Cc: Kevin Hilman --- include/linux/context_tracking.h | 31 +------------------- include/linux/context_tracking_state.h | 39 ++++++++++++++++++++++++++ 2 files changed, 40 insertions(+), 30 deletions(-) create mode 100644 include/linux/context_tracking_state.h diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h index e070ea5dadac..82ec4870e064 100644 --- a/include/linux/context_tracking.h +++ b/include/linux/context_tracking.h @@ -2,40 +2,12 @@ #define _LINUX_CONTEXT_TRACKING_H #include -#include #include -#include +#include #include -struct context_tracking { - /* - * When active is false, probes are unset in order - * to minimize overhead: TIF flags are cleared - * and calls to user_enter/exit are ignored. This - * may be further optimized using static keys. - */ - bool active; - enum ctx_state { - IN_KERNEL = 0, - IN_USER, - } state; -}; - #ifdef CONFIG_CONTEXT_TRACKING -extern struct static_key context_tracking_enabled; -DECLARE_PER_CPU(struct context_tracking, context_tracking); - -static inline bool context_tracking_in_user(void) -{ - return __this_cpu_read(context_tracking.state) == IN_USER; -} - -static inline bool context_tracking_active(void) -{ - return __this_cpu_read(context_tracking.active); -} - extern void context_tracking_cpu_set(int cpu); extern void context_tracking_user_enter(void); @@ -83,7 +55,6 @@ static inline void context_tracking_task_switch(struct task_struct *prev, __context_tracking_task_switch(prev, next); } #else -static inline bool context_tracking_in_user(void) { return false; } static inline void user_enter(void) { } static inline void user_exit(void) { } static inline enum ctx_state exception_enter(void) { return 0; } diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h new file mode 100644 index 000000000000..0f1979d0674f --- /dev/null +++ b/include/linux/context_tracking_state.h @@ -0,0 +1,39 @@ +#ifndef _LINUX_CONTEXT_TRACKING_STATE_H +#define _LINUX_CONTEXT_TRACKING_STATE_H + +#include +#include + +struct context_tracking { + /* + * When active is false, probes are unset in order + * to minimize overhead: TIF flags are cleared + * and calls to user_enter/exit are ignored. This + * may be further optimized using static keys. + */ + bool active; + enum ctx_state { + IN_KERNEL = 0, + IN_USER, + } state; +}; + +#ifdef CONFIG_CONTEXT_TRACKING +extern struct static_key context_tracking_enabled; +DECLARE_PER_CPU(struct context_tracking, context_tracking); + +static inline bool context_tracking_in_user(void) +{ + return __this_cpu_read(context_tracking.state) == IN_USER; +} + +static inline bool context_tracking_active(void) +{ + return __this_cpu_read(context_tracking.active); +} +#else +static inline bool context_tracking_in_user(void) { return false; } +static inline bool context_tracking_active(void) { return false; } +#endif /* CONFIG_CONTEXT_TRACKING */ + +#endif From 2d4b84739f0acf61f37267b4e80c5bd85fb90a7e Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Mon, 29 Jul 2013 20:29:43 +0200 Subject: [PATCH 15/24] hardirq: Split preempt count mask definitions In order to use static keys with vtime APIs, we'll need to add static keys headers to vtime.h hardirq.h then becomes a problem because it needs vtime.h for irqtime accounting in irq_enter/irq_exit, but it's often included just to get the irq mask definitions in the task preempt_count field and the APIs that come along: in_interrupt(), in_hardirq(), etc... Some very low level arch headers sometimes need these masks and APIs such as arch/m68k/include/asm/irqflags.h for example. But they don't want to include hardirq.h if vtime.h, jump_label.h and even workqueue.h come along. Including such bloated high level header from arch headers can quickly result in circular headers dependency that crash the build. So let's split hardirq.h in two parts: * preempt_mask.h that gathers all the preempt_count definitions and the APIs associated. This one is considered low level and can be safely included anywhere. * hardirq.h that includes the previous one. It defines the irq entry/exit APIs. To avoid future circular headers dependencies, the preempt_mask.h inclusion can replace hardirq.h on files that don't implement irq low level handlers but just need the atomic/context check APIs. Signed-off-by: Frederic Weisbecker Cc: Steven Rostedt Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Li Zhong Cc: Mike Galbraith Cc: Kevin Hilman --- include/linux/hardirq.h | 117 +-------------------------------- include/linux/preempt_mask.h | 122 +++++++++++++++++++++++++++++++++++ 2 files changed, 123 insertions(+), 116 deletions(-) create mode 100644 include/linux/preempt_mask.h diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h index 05bcc0903766..ccfe17c5c8da 100644 --- a/include/linux/hardirq.h +++ b/include/linux/hardirq.h @@ -1,126 +1,11 @@ #ifndef LINUX_HARDIRQ_H #define LINUX_HARDIRQ_H -#include +#include #include #include #include -#include -/* - * We put the hardirq and softirq counter into the preemption - * counter. The bitmask has the following meaning: - * - * - bits 0-7 are the preemption count (max preemption depth: 256) - * - bits 8-15 are the softirq count (max # of softirqs: 256) - * - * The hardirq count can in theory reach the same as NR_IRQS. - * In reality, the number of nested IRQS is limited to the stack - * size as well. For archs with over 1000 IRQS it is not practical - * to expect that they will all nest. We give a max of 10 bits for - * hardirq nesting. An arch may choose to give less than 10 bits. - * m68k expects it to be 8. - * - * - bits 16-25 are the hardirq count (max # of nested hardirqs: 1024) - * - bit 26 is the NMI_MASK - * - bit 27 is the PREEMPT_ACTIVE flag - * - * PREEMPT_MASK: 0x000000ff - * SOFTIRQ_MASK: 0x0000ff00 - * HARDIRQ_MASK: 0x03ff0000 - * NMI_MASK: 0x04000000 - */ -#define PREEMPT_BITS 8 -#define SOFTIRQ_BITS 8 -#define NMI_BITS 1 - -#define MAX_HARDIRQ_BITS 10 - -#ifndef HARDIRQ_BITS -# define HARDIRQ_BITS MAX_HARDIRQ_BITS -#endif - -#if HARDIRQ_BITS > MAX_HARDIRQ_BITS -#error HARDIRQ_BITS too high! -#endif - -#define PREEMPT_SHIFT 0 -#define SOFTIRQ_SHIFT (PREEMPT_SHIFT + PREEMPT_BITS) -#define HARDIRQ_SHIFT (SOFTIRQ_SHIFT + SOFTIRQ_BITS) -#define NMI_SHIFT (HARDIRQ_SHIFT + HARDIRQ_BITS) - -#define __IRQ_MASK(x) ((1UL << (x))-1) - -#define PREEMPT_MASK (__IRQ_MASK(PREEMPT_BITS) << PREEMPT_SHIFT) -#define SOFTIRQ_MASK (__IRQ_MASK(SOFTIRQ_BITS) << SOFTIRQ_SHIFT) -#define HARDIRQ_MASK (__IRQ_MASK(HARDIRQ_BITS) << HARDIRQ_SHIFT) -#define NMI_MASK (__IRQ_MASK(NMI_BITS) << NMI_SHIFT) - -#define PREEMPT_OFFSET (1UL << PREEMPT_SHIFT) -#define SOFTIRQ_OFFSET (1UL << SOFTIRQ_SHIFT) -#define HARDIRQ_OFFSET (1UL << HARDIRQ_SHIFT) -#define NMI_OFFSET (1UL << NMI_SHIFT) - -#define SOFTIRQ_DISABLE_OFFSET (2 * SOFTIRQ_OFFSET) - -#ifndef PREEMPT_ACTIVE -#define PREEMPT_ACTIVE_BITS 1 -#define PREEMPT_ACTIVE_SHIFT (NMI_SHIFT + NMI_BITS) -#define PREEMPT_ACTIVE (__IRQ_MASK(PREEMPT_ACTIVE_BITS) << PREEMPT_ACTIVE_SHIFT) -#endif - -#if PREEMPT_ACTIVE < (1 << (NMI_SHIFT + NMI_BITS)) -#error PREEMPT_ACTIVE is too low! -#endif - -#define hardirq_count() (preempt_count() & HARDIRQ_MASK) -#define softirq_count() (preempt_count() & SOFTIRQ_MASK) -#define irq_count() (preempt_count() & (HARDIRQ_MASK | SOFTIRQ_MASK \ - | NMI_MASK)) - -/* - * Are we doing bottom half or hardware interrupt processing? - * Are we in a softirq context? Interrupt context? - * in_softirq - Are we currently processing softirq or have bh disabled? - * in_serving_softirq - Are we currently processing softirq? - */ -#define in_irq() (hardirq_count()) -#define in_softirq() (softirq_count()) -#define in_interrupt() (irq_count()) -#define in_serving_softirq() (softirq_count() & SOFTIRQ_OFFSET) - -/* - * Are we in NMI context? - */ -#define in_nmi() (preempt_count() & NMI_MASK) - -#if defined(CONFIG_PREEMPT_COUNT) -# define PREEMPT_CHECK_OFFSET 1 -#else -# define PREEMPT_CHECK_OFFSET 0 -#endif - -/* - * Are we running in atomic context? WARNING: this macro cannot - * always detect atomic context; in particular, it cannot know about - * held spinlocks in non-preemptible kernels. Thus it should not be - * used in the general case to determine whether sleeping is possible. - * Do not use in_atomic() in driver code. - */ -#define in_atomic() ((preempt_count() & ~PREEMPT_ACTIVE) != 0) - -/* - * Check whether we were atomic before we did preempt_disable(): - * (used by the scheduler, *after* releasing the kernel lock) - */ -#define in_atomic_preempt_off() \ - ((preempt_count() & ~PREEMPT_ACTIVE) != PREEMPT_CHECK_OFFSET) - -#ifdef CONFIG_PREEMPT_COUNT -# define preemptible() (preempt_count() == 0 && !irqs_disabled()) -#else -# define preemptible() 0 -#endif #if defined(CONFIG_SMP) || defined(CONFIG_GENERIC_HARDIRQS) extern void synchronize_irq(unsigned int irq); diff --git a/include/linux/preempt_mask.h b/include/linux/preempt_mask.h new file mode 100644 index 000000000000..931bc616219f --- /dev/null +++ b/include/linux/preempt_mask.h @@ -0,0 +1,122 @@ +#ifndef LINUX_PREEMPT_MASK_H +#define LINUX_PREEMPT_MASK_H + +#include +#include + +/* + * We put the hardirq and softirq counter into the preemption + * counter. The bitmask has the following meaning: + * + * - bits 0-7 are the preemption count (max preemption depth: 256) + * - bits 8-15 are the softirq count (max # of softirqs: 256) + * + * The hardirq count can in theory reach the same as NR_IRQS. + * In reality, the number of nested IRQS is limited to the stack + * size as well. For archs with over 1000 IRQS it is not practical + * to expect that they will all nest. We give a max of 10 bits for + * hardirq nesting. An arch may choose to give less than 10 bits. + * m68k expects it to be 8. + * + * - bits 16-25 are the hardirq count (max # of nested hardirqs: 1024) + * - bit 26 is the NMI_MASK + * - bit 27 is the PREEMPT_ACTIVE flag + * + * PREEMPT_MASK: 0x000000ff + * SOFTIRQ_MASK: 0x0000ff00 + * HARDIRQ_MASK: 0x03ff0000 + * NMI_MASK: 0x04000000 + */ +#define PREEMPT_BITS 8 +#define SOFTIRQ_BITS 8 +#define NMI_BITS 1 + +#define MAX_HARDIRQ_BITS 10 + +#ifndef HARDIRQ_BITS +# define HARDIRQ_BITS MAX_HARDIRQ_BITS +#endif + +#if HARDIRQ_BITS > MAX_HARDIRQ_BITS +#error HARDIRQ_BITS too high! +#endif + +#define PREEMPT_SHIFT 0 +#define SOFTIRQ_SHIFT (PREEMPT_SHIFT + PREEMPT_BITS) +#define HARDIRQ_SHIFT (SOFTIRQ_SHIFT + SOFTIRQ_BITS) +#define NMI_SHIFT (HARDIRQ_SHIFT + HARDIRQ_BITS) + +#define __IRQ_MASK(x) ((1UL << (x))-1) + +#define PREEMPT_MASK (__IRQ_MASK(PREEMPT_BITS) << PREEMPT_SHIFT) +#define SOFTIRQ_MASK (__IRQ_MASK(SOFTIRQ_BITS) << SOFTIRQ_SHIFT) +#define HARDIRQ_MASK (__IRQ_MASK(HARDIRQ_BITS) << HARDIRQ_SHIFT) +#define NMI_MASK (__IRQ_MASK(NMI_BITS) << NMI_SHIFT) + +#define PREEMPT_OFFSET (1UL << PREEMPT_SHIFT) +#define SOFTIRQ_OFFSET (1UL << SOFTIRQ_SHIFT) +#define HARDIRQ_OFFSET (1UL << HARDIRQ_SHIFT) +#define NMI_OFFSET (1UL << NMI_SHIFT) + +#define SOFTIRQ_DISABLE_OFFSET (2 * SOFTIRQ_OFFSET) + +#ifndef PREEMPT_ACTIVE +#define PREEMPT_ACTIVE_BITS 1 +#define PREEMPT_ACTIVE_SHIFT (NMI_SHIFT + NMI_BITS) +#define PREEMPT_ACTIVE (__IRQ_MASK(PREEMPT_ACTIVE_BITS) << PREEMPT_ACTIVE_SHIFT) +#endif + +#if PREEMPT_ACTIVE < (1 << (NMI_SHIFT + NMI_BITS)) +#error PREEMPT_ACTIVE is too low! +#endif + +#define hardirq_count() (preempt_count() & HARDIRQ_MASK) +#define softirq_count() (preempt_count() & SOFTIRQ_MASK) +#define irq_count() (preempt_count() & (HARDIRQ_MASK | SOFTIRQ_MASK \ + | NMI_MASK)) + +/* + * Are we doing bottom half or hardware interrupt processing? + * Are we in a softirq context? Interrupt context? + * in_softirq - Are we currently processing softirq or have bh disabled? + * in_serving_softirq - Are we currently processing softirq? + */ +#define in_irq() (hardirq_count()) +#define in_softirq() (softirq_count()) +#define in_interrupt() (irq_count()) +#define in_serving_softirq() (softirq_count() & SOFTIRQ_OFFSET) + +/* + * Are we in NMI context? + */ +#define in_nmi() (preempt_count() & NMI_MASK) + +#if defined(CONFIG_PREEMPT_COUNT) +# define PREEMPT_CHECK_OFFSET 1 +#else +# define PREEMPT_CHECK_OFFSET 0 +#endif + +/* + * Are we running in atomic context? WARNING: this macro cannot + * always detect atomic context; in particular, it cannot know about + * held spinlocks in non-preemptible kernels. Thus it should not be + * used in the general case to determine whether sleeping is possible. + * Do not use in_atomic() in driver code. + */ +#define in_atomic() ((preempt_count() & ~PREEMPT_ACTIVE) != 0) + +/* + * Check whether we were atomic before we did preempt_disable(): + * (used by the scheduler, *after* releasing the kernel lock) + */ +#define in_atomic_preempt_off() \ + ((preempt_count() & ~PREEMPT_ACTIVE) != PREEMPT_CHECK_OFFSET) + +#ifdef CONFIG_PREEMPT_COUNT +# define preemptible() (preempt_count() == 0 && !irqs_disabled()) +#else +# define preemptible() 0 +#endif + +#endif /* LINUX_PREEMPT_MASK_H */ From a703f9b72407d9a4e233f4f6aea1a14ab2b74415 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Mon, 29 Jul 2013 21:06:21 +0200 Subject: [PATCH 16/24] m68k: hardirq_count() only need preempt_mask.h The m68k irqflags implementation needs to check hardirq context in some cases. As it is a very low level header file, it's better to include preempt_mask.h rather than hardirq.h when the only purpose is to use irq context APIs. This way we can avoid future header circular dependencies when vtime.h will expand to use static keys. Signed-off-by: Frederic Weisbecker Cc: Steven Rostedt Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Li Zhong Cc: Mike Galbraith Cc: Kevin Hilman Cc: Geert Uytterhoeven --- arch/m68k/include/asm/irqflags.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/m68k/include/asm/irqflags.h b/arch/m68k/include/asm/irqflags.h index 7ef4115b8c4a..4c6275522e67 100644 --- a/arch/m68k/include/asm/irqflags.h +++ b/arch/m68k/include/asm/irqflags.h @@ -3,7 +3,7 @@ #include #ifdef CONFIG_MMU -#include +#include #endif #include #include From a5725ac23bf4ff79656ac2c317c323e261327fb3 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Tue, 16 Jul 2013 18:50:52 +0200 Subject: [PATCH 17/24] vtime: Describe overriden functions in dedicated arch headers If the arch overrides some generic vtime APIs, let it describe these on a dedicated and standalone header. This way it becomes convenient to include it in vtime generic headers without irrelevant stuff in such a low level header. Signed-off-by: Frederic Weisbecker Cc: Steven Rostedt Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Li Zhong Cc: Mike Galbraith Cc: Kevin Hilman Cc: Martin Schwidefsky Cc: Heiko Carstens --- arch/ia64/include/asm/Kbuild | 1 + arch/powerpc/include/asm/Kbuild | 1 + arch/s390/include/asm/cputime.h | 3 --- arch/s390/include/asm/vtime.h | 7 +++++++ arch/s390/kernel/vtime.c | 1 + include/asm-generic/vtime.h | 0 include/linux/vtime.h | 4 ++++ 7 files changed, 14 insertions(+), 3 deletions(-) create mode 100644 arch/s390/include/asm/vtime.h create mode 100644 include/asm-generic/vtime.h diff --git a/arch/ia64/include/asm/Kbuild b/arch/ia64/include/asm/Kbuild index 05b03ecd7933..a3456f34f672 100644 --- a/arch/ia64/include/asm/Kbuild +++ b/arch/ia64/include/asm/Kbuild @@ -3,3 +3,4 @@ generic-y += clkdev.h generic-y += exec.h generic-y += kvm_para.h generic-y += trace_clock.h +generic-y += vtime.h \ No newline at end of file diff --git a/arch/powerpc/include/asm/Kbuild b/arch/powerpc/include/asm/Kbuild index 650757c300db..704e6f10ae80 100644 --- a/arch/powerpc/include/asm/Kbuild +++ b/arch/powerpc/include/asm/Kbuild @@ -2,3 +2,4 @@ generic-y += clkdev.h generic-y += rwsem.h generic-y += trace_clock.h +generic-y += vtime.h \ No newline at end of file diff --git a/arch/s390/include/asm/cputime.h b/arch/s390/include/asm/cputime.h index d2ff41370c0c..f65bd3634519 100644 --- a/arch/s390/include/asm/cputime.h +++ b/arch/s390/include/asm/cputime.h @@ -13,9 +13,6 @@ #include -#define __ARCH_HAS_VTIME_ACCOUNT -#define __ARCH_HAS_VTIME_TASK_SWITCH - /* We want to use full resolution of the CPU timer: 2**-12 micro-seconds. */ typedef unsigned long long __nocast cputime_t; diff --git a/arch/s390/include/asm/vtime.h b/arch/s390/include/asm/vtime.h new file mode 100644 index 000000000000..af9896c53eb3 --- /dev/null +++ b/arch/s390/include/asm/vtime.h @@ -0,0 +1,7 @@ +#ifndef _S390_VTIME_H +#define _S390_VTIME_H + +#define __ARCH_HAS_VTIME_ACCOUNT +#define __ARCH_HAS_VTIME_TASK_SWITCH + +#endif /* _S390_VTIME_H */ diff --git a/arch/s390/kernel/vtime.c b/arch/s390/kernel/vtime.c index 9b9c1b78ec67..abcfab55f99b 100644 --- a/arch/s390/kernel/vtime.c +++ b/arch/s390/kernel/vtime.c @@ -19,6 +19,7 @@ #include #include #include +#include #include #include "entry.h" diff --git a/include/asm-generic/vtime.h b/include/asm-generic/vtime.h new file mode 100644 index 000000000000..e69de29bb2d1 diff --git a/include/linux/vtime.h b/include/linux/vtime.h index b1dd2db80076..2ad073915e8c 100644 --- a/include/linux/vtime.h +++ b/include/linux/vtime.h @@ -1,6 +1,10 @@ #ifndef _LINUX_KERNEL_VTIME_H #define _LINUX_KERNEL_VTIME_H +#ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE +#include +#endif + struct task_struct; #ifdef CONFIG_VIRT_CPU_ACCOUNTING From b04934061330a4a449cfce703c97d887c3e11cd7 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Fri, 12 Jul 2013 03:10:15 +0200 Subject: [PATCH 18/24] vtime: Optimize full dynticks accounting off case with static keys If no CPU is in the full dynticks range, we can avoid the full dynticks cputime accounting through generic vtime along with its overhead and use the traditional tick based accounting instead. Let's do this and nope the off case with static keys. Signed-off-by: Frederic Weisbecker Cc: Steven Rostedt Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Li Zhong Cc: Mike Galbraith Cc: Kevin Hilman --- include/linux/context_tracking.h | 6 +-- include/linux/vtime.h | 70 ++++++++++++++++++++++++++++---- kernel/sched/cputime.c | 22 ++-------- 3 files changed, 67 insertions(+), 31 deletions(-) diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h index 82ec4870e064..158158704c30 100644 --- a/include/linux/context_tracking.h +++ b/include/linux/context_tracking.h @@ -74,8 +74,7 @@ static inline void context_tracking_init(void) { } #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN static inline void guest_enter(void) { - if (static_key_false(&context_tracking_enabled) && - vtime_accounting_enabled()) + if (vtime_accounting_enabled()) vtime_guest_enter(current); else current->flags |= PF_VCPU; @@ -83,8 +82,7 @@ static inline void guest_enter(void) static inline void guest_exit(void) { - if (static_key_false(&context_tracking_enabled) && - vtime_accounting_enabled()) + if (vtime_accounting_enabled()) vtime_guest_exit(current); else current->flags &= ~PF_VCPU; diff --git a/include/linux/vtime.h b/include/linux/vtime.h index 2ad073915e8c..f5b72b364bda 100644 --- a/include/linux/vtime.h +++ b/include/linux/vtime.h @@ -1,22 +1,68 @@ #ifndef _LINUX_KERNEL_VTIME_H #define _LINUX_KERNEL_VTIME_H +#include #ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE #include #endif + struct task_struct; +/* + * vtime_accounting_enabled() definitions/declarations + */ +#ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE +static inline bool vtime_accounting_enabled(void) { return true; } +#endif /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */ + +#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN +static inline bool vtime_accounting_enabled(void) +{ + if (static_key_false(&context_tracking_enabled)) { + if (context_tracking_active()) + return true; + } + + return false; +} +#endif /* CONFIG_VIRT_CPU_ACCOUNTING_GEN */ + +#ifndef CONFIG_VIRT_CPU_ACCOUNTING +static inline bool vtime_accounting_enabled(void) { return false; } +#endif /* !CONFIG_VIRT_CPU_ACCOUNTING */ + + +/* + * Common vtime APIs + */ #ifdef CONFIG_VIRT_CPU_ACCOUNTING + +#ifdef __ARCH_HAS_VTIME_TASK_SWITCH extern void vtime_task_switch(struct task_struct *prev); +#else +extern void vtime_common_task_switch(struct task_struct *prev); +static inline void vtime_task_switch(struct task_struct *prev) +{ + if (vtime_accounting_enabled()) + vtime_common_task_switch(prev); +} +#endif /* __ARCH_HAS_VTIME_TASK_SWITCH */ + extern void vtime_account_system(struct task_struct *tsk); extern void vtime_account_idle(struct task_struct *tsk); extern void vtime_account_user(struct task_struct *tsk); -extern void vtime_account_irq_enter(struct task_struct *tsk); -#ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE -static inline bool vtime_accounting_enabled(void) { return true; } -#endif +#ifdef __ARCH_HAS_VTIME_ACCOUNT +extern void vtime_account_irq_enter(struct task_struct *tsk); +#else +extern void vtime_common_account_irq_enter(struct task_struct *tsk); +static inline void vtime_account_irq_enter(struct task_struct *tsk) +{ + if (vtime_accounting_enabled()) + vtime_common_account_irq_enter(tsk); +} +#endif /* __ARCH_HAS_VTIME_ACCOUNT */ #else /* !CONFIG_VIRT_CPU_ACCOUNTING */ @@ -24,14 +70,20 @@ static inline void vtime_task_switch(struct task_struct *prev) { } static inline void vtime_account_system(struct task_struct *tsk) { } static inline void vtime_account_user(struct task_struct *tsk) { } static inline void vtime_account_irq_enter(struct task_struct *tsk) { } -static inline bool vtime_accounting_enabled(void) { return false; } -#endif +#endif /* !CONFIG_VIRT_CPU_ACCOUNTING */ #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN extern void arch_vtime_task_switch(struct task_struct *tsk); -extern void vtime_account_irq_exit(struct task_struct *tsk); -extern bool vtime_accounting_enabled(void); +extern void vtime_gen_account_irq_exit(struct task_struct *tsk); + +static inline void vtime_account_irq_exit(struct task_struct *tsk) +{ + if (vtime_accounting_enabled()) + vtime_gen_account_irq_exit(tsk); +} + extern void vtime_user_enter(struct task_struct *tsk); + static inline void vtime_user_exit(struct task_struct *tsk) { vtime_account_user(tsk); @@ -39,7 +91,7 @@ static inline void vtime_user_exit(struct task_struct *tsk) extern void vtime_guest_enter(struct task_struct *tsk); extern void vtime_guest_exit(struct task_struct *tsk); extern void vtime_init_idle(struct task_struct *tsk, int cpu); -#else +#else /* !CONFIG_VIRT_CPU_ACCOUNTING_GEN */ static inline void vtime_account_irq_exit(struct task_struct *tsk) { /* On hard|softirq exit we always account to hard|softirq cputime */ diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c index b62d5c027c7e..0831b06aab97 100644 --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -378,11 +378,8 @@ static inline void irqtime_account_process_tick(struct task_struct *p, int user_ #ifdef CONFIG_VIRT_CPU_ACCOUNTING #ifndef __ARCH_HAS_VTIME_TASK_SWITCH -void vtime_task_switch(struct task_struct *prev) +void vtime_common_task_switch(struct task_struct *prev) { - if (!vtime_accounting_enabled()) - return; - if (is_idle_task(prev)) vtime_account_idle(prev); else @@ -404,11 +401,8 @@ void vtime_task_switch(struct task_struct *prev) * vtime_account(). */ #ifndef __ARCH_HAS_VTIME_ACCOUNT -void vtime_account_irq_enter(struct task_struct *tsk) +void vtime_common_account_irq_enter(struct task_struct *tsk) { - if (!vtime_accounting_enabled()) - return; - if (!in_interrupt()) { /* * If we interrupted user, context_tracking_in_user() @@ -428,7 +422,7 @@ void vtime_account_irq_enter(struct task_struct *tsk) } vtime_account_system(tsk); } -EXPORT_SYMBOL_GPL(vtime_account_irq_enter); +EXPORT_SYMBOL_GPL(vtime_common_account_irq_enter); #endif /* __ARCH_HAS_VTIME_ACCOUNT */ #endif /* CONFIG_VIRT_CPU_ACCOUNTING */ @@ -669,11 +663,8 @@ void vtime_account_system(struct task_struct *tsk) write_sequnlock(&tsk->vtime_seqlock); } -void vtime_account_irq_exit(struct task_struct *tsk) +void vtime_gen_account_irq_exit(struct task_struct *tsk) { - if (!vtime_accounting_enabled()) - return; - write_seqlock(&tsk->vtime_seqlock); if (context_tracking_in_user()) tsk->vtime_snap_whence = VTIME_USER; @@ -732,11 +723,6 @@ void vtime_account_idle(struct task_struct *tsk) account_idle_time(delta_cpu); } -bool vtime_accounting_enabled(void) -{ - return context_tracking_active(); -} - void arch_vtime_task_switch(struct task_struct *prev) { write_seqlock(&prev->vtime_seqlock); From b854fafa4e06c50a92e00b39d75ee62083d986d6 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Sat, 13 Jul 2013 17:24:20 +0200 Subject: [PATCH 19/24] vtime: Always scale generic vtime accounting results The cputime accounting in full dynticks can be a subtle mixup of CPUs using tick based accounting and others using generic vtime. As long as the tick can have a share on producing these stats, we want to scale the result against CFS precise accounting as the tick can miss some task hiding between the periodic interrupt. Signed-off-by: Frederic Weisbecker Cc: Steven Rostedt Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Li Zhong Cc: Mike Galbraith Cc: Kevin Hilman --- kernel/sched/cputime.c | 6 ------ 1 file changed, 6 deletions(-) diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c index 0831b06aab97..e9e742ed7280 100644 --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -553,12 +553,6 @@ static void cputime_adjust(struct task_cputime *curr, { cputime_t rtime, stime, utime, total; - if (vtime_accounting_enabled()) { - *ut = curr->utime; - *st = curr->stime; - return; - } - stime = curr->stime; total = stime + curr->utime; From af2350bd12096dfd04e1090b90bfecea1f75f84e Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Mon, 15 Jul 2013 16:35:55 +0200 Subject: [PATCH 20/24] vtime: Always debug check snapshot source _before_ updating it The vtime delta update performed by get_vtime_delta() always check that the source of the snapshot is valid. Meanhile the snapshot updaters that rely on get_vtime_delta() also set the new snapshot origin. But some of them do this right before the call to get_vtime_delta(), making its debug check useless. This is easily fixable by moving the snapshot origin update after the call to get_vtime_delta(). The order doesn't matter there. Signed-off-by: Frederic Weisbecker Cc: Steven Rostedt Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Li Zhong Cc: Mike Galbraith Cc: Kevin Hilman --- kernel/sched/cputime.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c index e9e742ed7280..c1d7493825ae 100644 --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -660,9 +660,9 @@ void vtime_account_system(struct task_struct *tsk) void vtime_gen_account_irq_exit(struct task_struct *tsk) { write_seqlock(&tsk->vtime_seqlock); + __vtime_account_system(tsk); if (context_tracking_in_user()) tsk->vtime_snap_whence = VTIME_USER; - __vtime_account_system(tsk); write_sequnlock(&tsk->vtime_seqlock); } @@ -680,8 +680,8 @@ void vtime_account_user(struct task_struct *tsk) void vtime_user_enter(struct task_struct *tsk) { write_seqlock(&tsk->vtime_seqlock); - tsk->vtime_snap_whence = VTIME_USER; __vtime_account_system(tsk); + tsk->vtime_snap_whence = VTIME_USER; write_sequnlock(&tsk->vtime_seqlock); } From 73867dcd0792ad14fb31bfe73d09d9a4576f7fc2 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Wed, 24 Jul 2013 23:31:00 +0200 Subject: [PATCH 21/24] nohz: Rename a few state variables Rename the full dynticks's cpumask and cpumask state variables to some more exportable names. These will be used later from global headers to optimize the main full dynticks APIs in conjunction with static keys. Signed-off-by: Frederic Weisbecker Cc: Steven Rostedt Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Li Zhong Cc: Mike Galbraith Cc: Kevin Hilman --- kernel/time/tick-sched.c | 44 ++++++++++++++++++++-------------------- 1 file changed, 22 insertions(+), 22 deletions(-) diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 91a2528b5f44..b28dee43e644 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -149,8 +149,8 @@ static void tick_sched_handle(struct tick_sched *ts, struct pt_regs *regs) } #ifdef CONFIG_NO_HZ_FULL -static cpumask_var_t nohz_full_mask; -bool have_nohz_full_mask; +static cpumask_var_t tick_nohz_full_mask; +bool tick_nohz_full_running; static bool can_stop_full_tick(void) { @@ -183,7 +183,7 @@ static bool can_stop_full_tick(void) * Don't allow the user to think they can get * full NO_HZ with this machine. */ - WARN_ONCE(have_nohz_full_mask, + WARN_ONCE(tick_nohz_full_running, "NO_HZ FULL will not work with unstable sched clock"); return false; } @@ -240,11 +240,11 @@ static void nohz_full_kick_ipi(void *info) */ void tick_nohz_full_kick_all(void) { - if (!have_nohz_full_mask) + if (!tick_nohz_full_running) return; preempt_disable(); - smp_call_function_many(nohz_full_mask, + smp_call_function_many(tick_nohz_full_mask, nohz_full_kick_ipi, NULL, false); preempt_enable(); } @@ -272,10 +272,10 @@ void tick_nohz_task_switch(struct task_struct *tsk) int tick_nohz_full_cpu(int cpu) { - if (!have_nohz_full_mask) + if (!tick_nohz_full_running) return 0; - return cpumask_test_cpu(cpu, nohz_full_mask); + return cpumask_test_cpu(cpu, tick_nohz_full_mask); } /* Parse the boot-time nohz CPU list from the kernel parameters. */ @@ -283,18 +283,18 @@ static int __init tick_nohz_full_setup(char *str) { int cpu; - alloc_bootmem_cpumask_var(&nohz_full_mask); - if (cpulist_parse(str, nohz_full_mask) < 0) { + alloc_bootmem_cpumask_var(&tick_nohz_full_mask); + if (cpulist_parse(str, tick_nohz_full_mask) < 0) { pr_warning("NOHZ: Incorrect nohz_full cpumask\n"); return 1; } cpu = smp_processor_id(); - if (cpumask_test_cpu(cpu, nohz_full_mask)) { + if (cpumask_test_cpu(cpu, tick_nohz_full_mask)) { pr_warning("NO_HZ: Clearing %d from nohz_full range for timekeeping\n", cpu); - cpumask_clear_cpu(cpu, nohz_full_mask); + cpumask_clear_cpu(cpu, tick_nohz_full_mask); } - have_nohz_full_mask = true; + tick_nohz_full_running = true; return 1; } @@ -312,7 +312,7 @@ static int tick_nohz_cpu_down_callback(struct notifier_block *nfb, * If we handle the timekeeping duty for full dynticks CPUs, * we can't safely shutdown that CPU. */ - if (have_nohz_full_mask && tick_do_timer_cpu == cpu) + if (tick_nohz_full_running && tick_do_timer_cpu == cpu) return NOTIFY_BAD; break; } @@ -331,14 +331,14 @@ static int tick_nohz_init_all(void) int err = -1; #ifdef CONFIG_NO_HZ_FULL_ALL - if (!alloc_cpumask_var(&nohz_full_mask, GFP_KERNEL)) { + if (!alloc_cpumask_var(&tick_nohz_full_mask, GFP_KERNEL)) { pr_err("NO_HZ: Can't allocate full dynticks cpumask\n"); return err; } err = 0; - cpumask_setall(nohz_full_mask); - cpumask_clear_cpu(smp_processor_id(), nohz_full_mask); - have_nohz_full_mask = true; + cpumask_setall(tick_nohz_full_mask); + cpumask_clear_cpu(smp_processor_id(), tick_nohz_full_mask); + tick_nohz_full_running = true; #endif return err; } @@ -347,20 +347,20 @@ void __init tick_nohz_init(void) { int cpu; - if (!have_nohz_full_mask) { + if (!tick_nohz_full_running) { if (tick_nohz_init_all() < 0) return; } - for_each_cpu(cpu, nohz_full_mask) + for_each_cpu(cpu, tick_nohz_full_mask) context_tracking_cpu_set(cpu); cpu_notifier(tick_nohz_cpu_down_callback, 0); - cpulist_scnprintf(nohz_full_buf, sizeof(nohz_full_buf), nohz_full_mask); + cpulist_scnprintf(nohz_full_buf, sizeof(nohz_full_buf), tick_nohz_full_mask); pr_info("NO_HZ: Full dynticks CPUs: %s.\n", nohz_full_buf); } #else -#define have_nohz_full_mask (0) +#define tick_nohz_full_running (0) #endif /* @@ -738,7 +738,7 @@ static bool can_stop_idle_tick(int cpu, struct tick_sched *ts) return false; } - if (have_nohz_full_mask) { + if (tick_nohz_full_running) { /* * Keep the tick alive to guarantee timekeeping progression * if there are full dynticks CPUs around From 460775df4680b4593d8449bc171008578625a850 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Wed, 24 Jul 2013 23:52:27 +0200 Subject: [PATCH 22/24] nohz: Optimize full dynticks state checks with static keys These APIs are frequenctly accessed and priority is given to optimize the full dynticks off-case in order to let distros enable this feature without suffering from significant performance regressions. Let's inline these APIs and optimize them with static keys. Signed-off-by: Frederic Weisbecker Cc: Steven Rostedt Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Li Zhong Cc: Mike Galbraith Cc: Kevin Hilman --- include/linux/tick.h | 25 +++++++++++++++++++++++-- kernel/time/tick-sched.c | 14 ++------------ 2 files changed, 25 insertions(+), 14 deletions(-) diff --git a/include/linux/tick.h b/include/linux/tick.h index 9180f4b85e6d..c60b079e1b37 100644 --- a/include/linux/tick.h +++ b/include/linux/tick.h @@ -10,6 +10,8 @@ #include #include #include +#include +#include #ifdef CONFIG_GENERIC_CLOCKEVENTS @@ -158,15 +160,34 @@ static inline u64 get_cpu_iowait_time_us(int cpu, u64 *unused) { return -1; } # endif /* !CONFIG_NO_HZ_COMMON */ #ifdef CONFIG_NO_HZ_FULL +extern bool tick_nohz_full_running; +extern cpumask_var_t tick_nohz_full_mask; + +static inline bool tick_nohz_full_enabled(void) +{ + if (!static_key_false(&context_tracking_enabled)) + return false; + + return tick_nohz_full_running; +} + +static inline bool tick_nohz_full_cpu(int cpu) +{ + if (!tick_nohz_full_enabled()) + return false; + + return cpumask_test_cpu(cpu, tick_nohz_full_mask); +} + extern void tick_nohz_init(void); -extern int tick_nohz_full_cpu(int cpu); extern void tick_nohz_full_check(void); extern void tick_nohz_full_kick(void); extern void tick_nohz_full_kick_all(void); extern void tick_nohz_task_switch(struct task_struct *tsk); #else static inline void tick_nohz_init(void) { } -static inline int tick_nohz_full_cpu(int cpu) { return 0; } +static inline bool tick_nohz_full_enabled(void) { return false; } +static inline bool tick_nohz_full_cpu(int cpu) { return false; } static inline void tick_nohz_full_check(void) { } static inline void tick_nohz_full_kick(void) { } static inline void tick_nohz_full_kick_all(void) { } diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index b28dee43e644..0b7887389bd2 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -149,7 +149,7 @@ static void tick_sched_handle(struct tick_sched *ts, struct pt_regs *regs) } #ifdef CONFIG_NO_HZ_FULL -static cpumask_var_t tick_nohz_full_mask; +cpumask_var_t tick_nohz_full_mask; bool tick_nohz_full_running; static bool can_stop_full_tick(void) @@ -270,14 +270,6 @@ void tick_nohz_task_switch(struct task_struct *tsk) local_irq_restore(flags); } -int tick_nohz_full_cpu(int cpu) -{ - if (!tick_nohz_full_running) - return 0; - - return cpumask_test_cpu(cpu, tick_nohz_full_mask); -} - /* Parse the boot-time nohz CPU list from the kernel parameters. */ static int __init tick_nohz_full_setup(char *str) { @@ -359,8 +351,6 @@ void __init tick_nohz_init(void) cpulist_scnprintf(nohz_full_buf, sizeof(nohz_full_buf), tick_nohz_full_mask); pr_info("NO_HZ: Full dynticks CPUs: %s.\n", nohz_full_buf); } -#else -#define tick_nohz_full_running (0) #endif /* @@ -738,7 +728,7 @@ static bool can_stop_idle_tick(int cpu, struct tick_sched *ts) return false; } - if (tick_nohz_full_running) { + if (tick_nohz_full_enabled()) { /* * Keep the tick alive to guarantee timekeeping progression * if there are full dynticks CPUs around From d13508f9440e46dccac6a2dd48d51a73b2207482 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Wed, 24 Jul 2013 23:52:27 +0200 Subject: [PATCH 23/24] nohz: Optimize full dynticks's sched hooks with static keys Scheduler IPIs and task context switches are serious fast path. Let's try to hide as much as we can the impact of full dynticks APIs' off case that are called on these sites through the use of static keys. Signed-off-by: Frederic Weisbecker Cc: Steven Rostedt Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Li Zhong Cc: Mike Galbraith Cc: Kevin Hilman --- include/linux/tick.h | 20 ++++++++++++++++---- kernel/time/tick-sched.c | 8 ++++---- 2 files changed, 20 insertions(+), 8 deletions(-) diff --git a/include/linux/tick.h b/include/linux/tick.h index c60b079e1b37..a7ef1d6fceb6 100644 --- a/include/linux/tick.h +++ b/include/linux/tick.h @@ -180,20 +180,32 @@ static inline bool tick_nohz_full_cpu(int cpu) } extern void tick_nohz_init(void); -extern void tick_nohz_full_check(void); +extern void __tick_nohz_full_check(void); extern void tick_nohz_full_kick(void); extern void tick_nohz_full_kick_all(void); -extern void tick_nohz_task_switch(struct task_struct *tsk); +extern void __tick_nohz_task_switch(struct task_struct *tsk); #else static inline void tick_nohz_init(void) { } static inline bool tick_nohz_full_enabled(void) { return false; } static inline bool tick_nohz_full_cpu(int cpu) { return false; } -static inline void tick_nohz_full_check(void) { } +static inline void __tick_nohz_full_check(void) { } static inline void tick_nohz_full_kick(void) { } static inline void tick_nohz_full_kick_all(void) { } -static inline void tick_nohz_task_switch(struct task_struct *tsk) { } +static inline void __tick_nohz_task_switch(struct task_struct *tsk) { } #endif +static inline void tick_nohz_full_check(void) +{ + if (tick_nohz_full_enabled()) + __tick_nohz_full_check(); +} + +static inline void tick_nohz_task_switch(struct task_struct *tsk) +{ + if (tick_nohz_full_enabled()) + __tick_nohz_task_switch(tsk); +} + # ifdef CONFIG_CPU_IDLE_GOV_MENU extern void menu_hrtimer_cancel(void); diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 0b7887389bd2..0ff6ae710161 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -198,7 +198,7 @@ static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now); * Re-evaluate the need for the tick on the current CPU * and restart it if necessary. */ -void tick_nohz_full_check(void) +void __tick_nohz_full_check(void) { struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); @@ -212,7 +212,7 @@ void tick_nohz_full_check(void) static void nohz_full_kick_work_func(struct irq_work *work) { - tick_nohz_full_check(); + __tick_nohz_full_check(); } static DEFINE_PER_CPU(struct irq_work, nohz_full_kick_work) = { @@ -231,7 +231,7 @@ void tick_nohz_full_kick(void) static void nohz_full_kick_ipi(void *info) { - tick_nohz_full_check(); + __tick_nohz_full_check(); } /* @@ -254,7 +254,7 @@ void tick_nohz_full_kick_all(void) * It might need the tick due to per task/process properties: * perf events, posix cpu timers, ... */ -void tick_nohz_task_switch(struct task_struct *tsk) +void __tick_nohz_task_switch(struct task_struct *tsk) { unsigned long flags; From c2e7fcf53c3cb02b4ada1c66a9bc8a4d97d58aba Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Fri, 2 Aug 2013 18:29:56 +0200 Subject: [PATCH 24/24] nohz: Include local CPU in full dynticks global kick tick_nohz_full_kick_all() is useful to notify all full dynticks CPUs that there is a system state change to checkout before re-evaluating the need for the tick. Unfortunately this is implemented using smp_call_function_many() that ignores the local CPU. This CPU also needs to re-evaluate the tick. on_each_cpu_mask() is not useful either because we don't want to re-evaluate the tick state in place but asynchronously from an IPI to avoid messing up with any random locking scenario. So lets call tick_nohz_full_kick() from tick_nohz_full_kick_all() so that the usual irq work takes care of it. Signed-off-by: Frederic Weisbecker Cc: Steven Rostedt Cc: Paul E. McKenney Cc: Borislav Petkov Cc: Li Zhong Cc: Mike Galbraith Cc: Kevin Hilman Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/1375460996-16329-4-git-send-email-fweisbec@gmail.com Signed-off-by: Ingo Molnar --- kernel/time/tick-sched.c | 1 + 1 file changed, 1 insertion(+) diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index adea6fc3ba2a..3612fc77f834 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -246,6 +246,7 @@ void tick_nohz_full_kick_all(void) preempt_disable(); smp_call_function_many(tick_nohz_full_mask, nohz_full_kick_ipi, NULL, false); + tick_nohz_full_kick(); preempt_enable(); }