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perf: Add AUX area to ring buffer for raw data streams

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This patch introduces "AUX space" in the perf mmap buffer, intended for
exporting high bandwidth data streams to userspace, such as instruction
flow traces.

AUX space is a ring buffer, defined by aux_{offset,size} fields in the
user_page structure, and read/write pointers aux_{head,tail}, which abide
by the same rules as data_* counterparts of the main perf buffer.

In order to allocate/mmap AUX, userspace needs to set up aux_offset to
such an offset that will be greater than data_offset+data_size and
aux_size to be the desired buffer size. Both need to be page aligned.
Then, same aux_offset and aux_size should be passed to mmap() call and
if everything adds up, you should have an AUX buffer as a result.

Pages that are mapped into this buffer also come out of user's mlock
rlimit plus perf_event_mlock_kb allowance.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kaixu Xia <kaixu.xia@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Robert Richter <rric@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: acme@infradead.org
Cc: adrian.hunter@intel.com
Cc: kan.liang@intel.com
Cc: markus.t.metzger@intel.com
Cc: mathieu.poirier@linaro.org
Link: http://lkml.kernel.org/r/1421237903-181015-3-git-send-email-alexander.shishkin@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2015-01-14 14:18:11 +02:00 committed by Ingo Molnar
parent e8c6deac69
commit 45bfb2e504
5 changed files with 268 additions and 32 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

17
include/linux/perf_event.h
View file

@ -284,6 +284,18 @@ struct pmu {
* Return the count value for a counter.
*/
u64 (*count) (struct perf_event *event); /*optional*/
/*
* Set up pmu-private data structures for an AUX area
*/
void *(*setup_aux) (int cpu, void **pages,
int nr_pages, bool overwrite);
/* optional */
/*
* Free pmu-private AUX data structures
*/
void (*free_aux) (void *aux); /* optional */
};
/**
@ -862,6 +874,11 @@ static inline bool needs_branch_stack(struct perf_event *event)
return event->attr.branch_sample_type != 0;
}
static inline bool has_aux(struct perf_event *event)
{
return event->pmu->setup_aux;
}
extern int perf_output_begin(struct perf_output_handle *handle,
struct perf_event *event, unsigned int size);
extern void perf_output_end(struct perf_output_handle *handle);

16
include/uapi/linux/perf_event.h
View file

@ -530,6 +530,22 @@ struct perf_event_mmap_page {
__u64 data_tail; /* user-space written tail */
__u64 data_offset; /* where the buffer starts */
__u64 data_size; /* data buffer size */
/*
* AUX area is defined by aux_{offset,size} fields that should be set
* by the userspace, so that
*
* aux_offset >= data_offset + data_size
*
* prior to mmap()ing it. Size of the mmap()ed area should be aux_size.
*
* Ring buffer pointers aux_{head,tail} have the same semantics as
* data_{head,tail} and same ordering rules apply.
*/
__u64 aux_head;
__u64 aux_tail;
__u64 aux_offset;
__u64 aux_size;
};
#define PERF_RECORD_MISC_CPUMODE_MASK (7 << 0)

147
kernel/events/core.c
View file

@ -4306,6 +4306,9 @@ static void perf_mmap_open(struct vm_area_struct *vma)
atomic_inc(&event->mmap_count);
atomic_inc(&event->rb->mmap_count);
if (vma->vm_pgoff)
atomic_inc(&event->rb->aux_mmap_count);
if (event->pmu->event_mapped)
event->pmu->event_mapped(event);
}
@ -4330,6 +4333,20 @@ static void perf_mmap_close(struct vm_area_struct *vma)
if (event->pmu->event_unmapped)
event->pmu->event_unmapped(event);
/*
* rb->aux_mmap_count will always drop before rb->mmap_count and
* event->mmap_count, so it is ok to use event->mmap_mutex to
* serialize with perf_mmap here.
*/
if (rb_has_aux(rb) && vma->vm_pgoff == rb->aux_pgoff &&
atomic_dec_and_mutex_lock(&rb->aux_mmap_count, &event->mmap_mutex)) {
atomic_long_sub(rb->aux_nr_pages, &mmap_user->locked_vm);
vma->vm_mm->pinned_vm -= rb->aux_mmap_locked;
rb_free_aux(rb);
mutex_unlock(&event->mmap_mutex);
}
atomic_dec(&rb->mmap_count);
if (!atomic_dec_and_mutex_lock(&event->mmap_count, &event->mmap_mutex))
@ -4403,7 +4420,7 @@ static void perf_mmap_close(struct vm_area_struct *vma)
static const struct vm_operations_struct perf_mmap_vmops = {
.open = perf_mmap_open,
.close = perf_mmap_close,
.close = perf_mmap_close, /* non mergable */
.fault = perf_mmap_fault,
.page_mkwrite = perf_mmap_fault,
};
@ -4414,10 +4431,10 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
unsigned long user_locked, user_lock_limit;
struct user_struct *user = current_user();
unsigned long locked, lock_limit;
struct ring_buffer *rb;
struct ring_buffer *rb = NULL;
unsigned long vma_size;
unsigned long nr_pages;
long user_extra, extra;
long user_extra = 0, extra = 0;
int ret = 0, flags = 0;
/*
@ -4432,7 +4449,66 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
return -EINVAL;
vma_size = vma->vm_end - vma->vm_start;
nr_pages = (vma_size / PAGE_SIZE) - 1;
if (vma->vm_pgoff == 0) {
nr_pages = (vma_size / PAGE_SIZE) - 1;
} else {
/*
* AUX area mapping: if rb->aux_nr_pages != 0, it's already
* mapped, all subsequent mappings should have the same size
* and offset. Must be above the normal perf buffer.
*/
u64 aux_offset, aux_size;
if (!event->rb)
return -EINVAL;
nr_pages = vma_size / PAGE_SIZE;
mutex_lock(&event->mmap_mutex);
ret = -EINVAL;
rb = event->rb;
if (!rb)
goto aux_unlock;
aux_offset = ACCESS_ONCE(rb->user_page->aux_offset);
aux_size = ACCESS_ONCE(rb->user_page->aux_size);
if (aux_offset < perf_data_size(rb) + PAGE_SIZE)
goto aux_unlock;
if (aux_offset != vma->vm_pgoff << PAGE_SHIFT)
goto aux_unlock;
/* already mapped with a different offset */
if (rb_has_aux(rb) && rb->aux_pgoff != vma->vm_pgoff)
goto aux_unlock;
if (aux_size != vma_size || aux_size != nr_pages * PAGE_SIZE)
goto aux_unlock;
/* already mapped with a different size */
if (rb_has_aux(rb) && rb->aux_nr_pages != nr_pages)
goto aux_unlock;
if (!is_power_of_2(nr_pages))
goto aux_unlock;
if (!atomic_inc_not_zero(&rb->mmap_count))
goto aux_unlock;
if (rb_has_aux(rb)) {
atomic_inc(&rb->aux_mmap_count);
ret = 0;
goto unlock;
}
atomic_set(&rb->aux_mmap_count, 1);
user_extra = nr_pages;
goto accounting;
}
/*
* If we have rb pages ensure they're a power-of-two number, so we
@ -4444,9 +4520,6 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
if (vma_size != PAGE_SIZE * (1 + nr_pages))
return -EINVAL;
if (vma->vm_pgoff != 0)
return -EINVAL;
WARN_ON_ONCE(event->ctx->parent_ctx);
again:
mutex_lock(&event->mmap_mutex);
@ -4470,6 +4543,8 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
}
user_extra = nr_pages + 1;
accounting:
user_lock_limit = sysctl_perf_event_mlock >> (PAGE_SHIFT - 10);
/*
@ -4479,7 +4554,6 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
user_locked = atomic_long_read(&user->locked_vm) + user_extra;
extra = 0;
if (user_locked > user_lock_limit)
extra = user_locked - user_lock_limit;
@ -4493,35 +4567,45 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
goto unlock;
}
WARN_ON(event->rb);
WARN_ON(!rb && event->rb);
if (vma->vm_flags & VM_WRITE)
flags |= RING_BUFFER_WRITABLE;
rb = rb_alloc(nr_pages,
event->attr.watermark ? event->attr.wakeup_watermark : 0,
event->cpu, flags);
if (!rb) {
ret = -ENOMEM;
goto unlock;
rb = rb_alloc(nr_pages,
event->attr.watermark ? event->attr.wakeup_watermark : 0,
event->cpu, flags);
if (!rb) {
ret = -ENOMEM;
goto unlock;
}
atomic_set(&rb->mmap_count, 1);
rb->mmap_user = get_current_user();
rb->mmap_locked = extra;
ring_buffer_attach(event, rb);
perf_event_init_userpage(event);
perf_event_update_userpage(event);
} else {
ret = rb_alloc_aux(rb, event, vma->vm_pgoff, nr_pages, flags);
if (!ret)
rb->aux_mmap_locked = extra;
}
atomic_set(&rb->mmap_count, 1);
rb->mmap_locked = extra;
rb->mmap_user = get_current_user();
atomic_long_add(user_extra, &user->locked_vm);
vma->vm_mm->pinned_vm += extra;
ring_buffer_attach(event, rb);
perf_event_init_userpage(event);
perf_event_update_userpage(event);
unlock:
if (!ret)
if (!ret) {
atomic_long_add(user_extra, &user->locked_vm);
vma->vm_mm->pinned_vm += extra;
atomic_inc(&event->mmap_count);
} else if (rb) {
atomic_dec(&rb->mmap_count);
}
aux_unlock:
mutex_unlock(&event->mmap_mutex);
/*
@ -7506,6 +7590,13 @@ perf_event_set_output(struct perf_event *event, struct perf_event *output_event)
if (output_event->clock != event->clock)
goto out;
/*
* If both events generate aux data, they must be on the same PMU
*/
if (has_aux(event) && has_aux(output_event) &&
event->pmu != output_event->pmu)
goto out;
set:
mutex_lock(&event->mmap_mutex);
/* Can't redirect output if we've got an active mmap() */

23
kernel/events/internal.h
View file

@ -35,6 +35,16 @@ struct ring_buffer {
unsigned long mmap_locked;
struct user_struct *mmap_user;
/* AUX area */
unsigned long aux_pgoff;
int aux_nr_pages;
atomic_t aux_mmap_count;
unsigned long aux_mmap_locked;
void (*free_aux)(void *);
atomic_t aux_refcount;
void **aux_pages;
void *aux_priv;
struct perf_event_mmap_page *user_page;
void *data_pages[0];
};
@ -43,6 +53,14 @@ extern void rb_free(struct ring_buffer *rb);
extern struct ring_buffer *
rb_alloc(int nr_pages, long watermark, int cpu, int flags);
extern void perf_event_wakeup(struct perf_event *event);
extern int rb_alloc_aux(struct ring_buffer *rb, struct perf_event *event,
pgoff_t pgoff, int nr_pages, int flags);
extern void rb_free_aux(struct ring_buffer *rb);
static inline bool rb_has_aux(struct ring_buffer *rb)
{
return !!rb->aux_nr_pages;
}
extern void
perf_event_header__init_id(struct perf_event_header *header,
@ -81,6 +99,11 @@ static inline unsigned long perf_data_size(struct ring_buffer *rb)
return rb->nr_pages << (PAGE_SHIFT + page_order(rb));
}
static inline unsigned long perf_aux_size(struct ring_buffer *rb)
{
return rb->aux_nr_pages << PAGE_SHIFT;
}
#define DEFINE_OUTPUT_COPY(func_name, memcpy_func) \
static inline unsigned long \
func_name(struct perf_output_handle *handle, \

97
kernel/events/ring_buffer.c
View file

@ -243,14 +243,87 @@ ring_buffer_init(struct ring_buffer *rb, long watermark, int flags)
spin_lock_init(&rb->event_lock);
}
int rb_alloc_aux(struct ring_buffer *rb, struct perf_event *event,
pgoff_t pgoff, int nr_pages, int flags)
{
bool overwrite = !(flags & RING_BUFFER_WRITABLE);
int node = (event->cpu == -1) ? -1 : cpu_to_node(event->cpu);
int ret = -ENOMEM;
if (!has_aux(event))
return -ENOTSUPP;
rb->aux_pages = kzalloc_node(nr_pages * sizeof(void *), GFP_KERNEL, node);
if (!rb->aux_pages)
return -ENOMEM;
rb->free_aux = event->pmu->free_aux;
for (rb->aux_nr_pages = 0; rb->aux_nr_pages < nr_pages;
rb->aux_nr_pages++) {
struct page *page;
page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
if (!page)
goto out;
rb->aux_pages[rb->aux_nr_pages] = page_address(page);
}
rb->aux_priv = event->pmu->setup_aux(event->cpu, rb->aux_pages, nr_pages,
overwrite);
if (!rb->aux_priv)
goto out;
ret = 0;
/*
* aux_pages (and pmu driver's private data, aux_priv) will be
* referenced in both producer's and consumer's contexts, thus
* we keep a refcount here to make sure either of the two can
* reference them safely.
*/
atomic_set(&rb->aux_refcount, 1);
out:
if (!ret)
rb->aux_pgoff = pgoff;
else
rb_free_aux(rb);
return ret;
}
static void __rb_free_aux(struct ring_buffer *rb)
{
int pg;
if (rb->aux_priv) {
rb->free_aux(rb->aux_priv);
rb->free_aux = NULL;
rb->aux_priv = NULL;
}
for (pg = 0; pg < rb->aux_nr_pages; pg++)
free_page((unsigned long)rb->aux_pages[pg]);
kfree(rb->aux_pages);
rb->aux_nr_pages = 0;
}
void rb_free_aux(struct ring_buffer *rb)
{
if (atomic_dec_and_test(&rb->aux_refcount))
__rb_free_aux(rb);
}
#ifndef CONFIG_PERF_USE_VMALLOC
/*
* Back perf_mmap() with regular GFP_KERNEL-0 pages.
*/
struct page *
perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
static struct page *
__perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
{
if (pgoff > rb->nr_pages)
return NULL;
@ -340,8 +413,8 @@ static int data_page_nr(struct ring_buffer *rb)
return rb->nr_pages << page_order(rb);
}
struct page *
perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
static struct page *
__perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
{
/* The '>' counts in the user page. */
if (pgoff > data_page_nr(rb))
@ -416,3 +489,19 @@ struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
}
#endif
struct page *
perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
{
if (rb->aux_nr_pages) {
/* above AUX space */
if (pgoff > rb->aux_pgoff + rb->aux_nr_pages)
return NULL;
/* AUX space */
if (pgoff >= rb->aux_pgoff)
return virt_to_page(rb->aux_pages[pgoff - rb->aux_pgoff]);
}
return __perf_mmap_to_page(rb, pgoff);
}