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posix-cpu-timers: Optimize run_posix_cpu_timers()

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We can optimize and simplify things taking into account signal->cputimer
is always running when we have configured any process wide cpu timer.

In check_process_timers(), we don't have to check if new updated value of
signal->cputime_expires is smaller, since we maintain new first expiration
time ({prof,virt,sched}_expires) in code flow and all other writes to
expiration cache are protected by sighand->siglock .

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Stanislaw Gruszka 2010-04-27 14:12:15 -07:00 committed by Thomas Gleixner
parent dbb6be6d5e
commit 29f87b793d
1 changed files with 29 additions and 51 deletions
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80
kernel/posix-cpu-timers.c
View file

@ -1002,16 +1002,9 @@ static void stop_process_timers(struct signal_struct *sig)
struct thread_group_cputimer *cputimer = &sig->cputimer;
unsigned long flags;
if (!cputimer->running)
return;
spin_lock_irqsave(&cputimer->lock, flags);
cputimer->running = 0;
spin_unlock_irqrestore(&cputimer->lock, flags);
sig->cputime_expires.prof_exp = cputime_zero;
sig->cputime_expires.virt_exp = cputime_zero;
sig->cputime_expires.sched_exp = 0;
}
static u32 onecputick;
@ -1048,6 +1041,23 @@ static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
}
}
/**
* task_cputime_zero - Check a task_cputime struct for all zero fields.
*
* @cputime: The struct to compare.
*
* Checks @cputime to see if all fields are zero. Returns true if all fields
* are zero, false if any field is nonzero.
*/
static inline int task_cputime_zero(const struct task_cputime *cputime)
{
if (cputime_eq(cputime->utime, cputime_zero) &&
cputime_eq(cputime->stime, cputime_zero) &&
cputime->sum_exec_runtime == 0)
return 1;
return 0;
}
/*
* Check for any per-thread CPU timers that have fired and move them
* off the tsk->*_timers list onto the firing list. Per-thread timers
@ -1064,19 +1074,6 @@ static void check_process_timers(struct task_struct *tsk,
struct task_cputime cputime;
unsigned long soft;
/*
* Don't sample the current process CPU clocks if there are no timers.
*/
if (list_empty(&timers[CPUCLOCK_PROF]) &&
cputime_eq(sig->it[CPUCLOCK_PROF].expires, cputime_zero) &&
sig->rlim[RLIMIT_CPU].rlim_cur == RLIM_INFINITY &&
list_empty(&timers[CPUCLOCK_VIRT]) &&
cputime_eq(sig->it[CPUCLOCK_VIRT].expires, cputime_zero) &&
list_empty(&timers[CPUCLOCK_SCHED])) {
stop_process_timers(sig);
return;
}
/*
* Collect the current process totals.
*/
@ -1166,18 +1163,11 @@ static void check_process_timers(struct task_struct *tsk,
}
}
if (!cputime_eq(prof_expires, cputime_zero) &&
(cputime_eq(sig->cputime_expires.prof_exp, cputime_zero) ||
cputime_gt(sig->cputime_expires.prof_exp, prof_expires)))
sig->cputime_expires.prof_exp = prof_expires;
if (!cputime_eq(virt_expires, cputime_zero) &&
(cputime_eq(sig->cputime_expires.virt_exp, cputime_zero) ||
cputime_gt(sig->cputime_expires.virt_exp, virt_expires)))
sig->cputime_expires.virt_exp = virt_expires;
if (sched_expires != 0 &&
(sig->cputime_expires.sched_exp == 0 ||
sig->cputime_expires.sched_exp > sched_expires))
sig->cputime_expires.sched_exp = sched_expires;
sig->cputime_expires.prof_exp = prof_expires;
sig->cputime_expires.virt_exp = virt_expires;
sig->cputime_expires.sched_exp = sched_expires;
if (task_cputime_zero(&sig->cputime_expires))
stop_process_timers(sig);
}
/*
@ -1249,23 +1239,6 @@ void posix_cpu_timer_schedule(struct k_itimer *timer)
++timer->it_requeue_pending;
}
/**
* task_cputime_zero - Check a task_cputime struct for all zero fields.
*
* @cputime: The struct to compare.
*
* Checks @cputime to see if all fields are zero. Returns true if all fields
* are zero, false if any field is nonzero.
*/
static inline int task_cputime_zero(const struct task_cputime *cputime)
{
if (cputime_eq(cputime->utime, cputime_zero) &&
cputime_eq(cputime->stime, cputime_zero) &&
cputime->sum_exec_runtime == 0)
return 1;
return 0;
}
/**
* task_cputime_expired - Compare two task_cputime entities.
*
@ -1322,7 +1295,7 @@ static inline int fastpath_timer_check(struct task_struct *tsk)
}
sig = tsk->signal;
if (!task_cputime_zero(&sig->cputime_expires)) {
if (sig->cputimer.running) {
struct task_cputime group_sample;
thread_group_cputimer(tsk, &group_sample);
@ -1359,7 +1332,12 @@ void run_posix_cpu_timers(struct task_struct *tsk)
* put them on the firing list.
*/
check_thread_timers(tsk, &firing);
check_process_timers(tsk, &firing);
/*
* If there are any active process wide timers (POSIX 1.b, itimers,
* RLIMIT_CPU) cputimer must be running.
*/
if (tsk->signal->cputimer.running)
check_process_timers(tsk, &firing);
/*
* We must release these locks before taking any timer's lock.