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Commit 1a594131 authored by Alexander Shishkin's avatar Alexander Shishkin Committed by Ingo Molnar
Browse files

perf: Add wakeup watermark control to the AUX area 



When AUX area gets a certain amount of new data, we want to wake up
userspace to collect it. This adds a new control to specify how much
data will cause a wakeup. This is then passed down to pmu drivers via
output handle's "wakeup" field, so that the driver can find the nearest
point where it can generate an interrupt.

We repurpose __reserved_2 in the event attribute for this, even though
it was never checked to be zero before, aux_watermark will only matter
for new AUX-aware code, so the old code should still be fine.

Signed-off-by: default avatarAlexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
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/1421237903-181015-10-git-send-email-alexander.shishkin@linux.intel.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 2023a0d2

include/uapi/linux/perf_event.h

+7 −0
Original line number Original line Diff line number Diff line
@@ -261,6 +261,7 @@ enum perf_event_read_format { 
#define PERF_ATTR_SIZE_VER3	96	/* add: sample_regs_user */

#define PERF_ATTR_SIZE_VER3	96	/* add: sample_regs_user */

					/* add: sample_stack_user */

					/* add: sample_stack_user */

#define PERF_ATTR_SIZE_VER4	104	/* add: sample_regs_intr */

#define PERF_ATTR_SIZE_VER4	104	/* add: sample_regs_intr */

#define PERF_ATTR_SIZE_VER5	112	/* add: aux_watermark */





/*

/*

 * Hardware event_id to monitor via a performance monitoring event:

 * Hardware event_id to monitor via a performance monitoring event:
@@ -366,6 +367,12 @@ struct perf_event_attr { 
	 * See asm/perf_regs.h for details.

	 * See asm/perf_regs.h for details.

	 */

	 */

	__u64	sample_regs_intr;

	__u64	sample_regs_intr;



	/*

	 * Wakeup watermark for AUX area

	 */

	__u32	aux_watermark;

	__u32	__reserved_2;	/* align to __u64 */

};

};





#define perf_flags(attr)	(*(&(attr)->read_format + 1))

#define perf_flags(attr)	(*(&(attr)->read_format + 1))

kernel/events/core.c

+2 −1
Original line number Original line Diff line number Diff line
@@ -4677,7 +4677,8 @@ accounting: 
		perf_event_init_userpage(event);

		perf_event_init_userpage(event);

		perf_event_update_userpage(event);

		perf_event_update_userpage(event);

	} else {

	} else {

		ret = rb_alloc_aux(rb, event, vma->vm_pgoff, nr_pages, flags);

		ret = rb_alloc_aux(rb, event, vma->vm_pgoff, nr_pages,

				   event->attr.aux_watermark, flags);

		if (!ret)

		if (!ret)

			rb->aux_mmap_locked = extra;

			rb->aux_mmap_locked = extra;

	}

	}

kernel/events/internal.h

+3 −1
Original line number Original line Diff line number Diff line
@@ -27,6 +27,7 @@ struct ring_buffer { 
	local_t				lost;		/* nr records lost   */

	local_t				lost;		/* nr records lost   */





	long				watermark;	/* wakeup watermark  */

	long				watermark;	/* wakeup watermark  */

	long				aux_watermark;

	/* poll crap */

	/* poll crap */

	spinlock_t			event_lock;

	spinlock_t			event_lock;

	struct list_head		event_list;

	struct list_head		event_list;
@@ -38,6 +39,7 @@ struct ring_buffer { 
	/* AUX area */

	/* AUX area */

	local_t				aux_head;

	local_t				aux_head;

	local_t				aux_nest;

	local_t				aux_nest;

	local_t				aux_wakeup;

	unsigned long			aux_pgoff;

	unsigned long			aux_pgoff;

	int				aux_nr_pages;

	int				aux_nr_pages;

	int				aux_overwrite;

	int				aux_overwrite;
@@ -57,7 +59,7 @@ extern struct ring_buffer * 
rb_alloc(int nr_pages, long watermark, int cpu, int flags);

rb_alloc(int nr_pages, long watermark, int cpu, int flags);

extern void perf_event_wakeup(struct perf_event *event);

extern void perf_event_wakeup(struct perf_event *event);

extern int rb_alloc_aux(struct ring_buffer *rb, 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);

			pgoff_t pgoff, int nr_pages, long watermark, int flags);

extern void rb_free_aux(struct ring_buffer *rb);

extern void rb_free_aux(struct ring_buffer *rb);

extern struct ring_buffer *ring_buffer_get(struct perf_event *event);

extern struct ring_buffer *ring_buffer_get(struct perf_event *event);

extern void ring_buffer_put(struct ring_buffer *rb);

extern void ring_buffer_put(struct ring_buffer *rb);

kernel/events/ring_buffer.c

+19 −3
Original line number Original line Diff line number Diff line
@@ -296,6 +296,7 @@ void *perf_aux_output_begin(struct perf_output_handle *handle, 
	 */

	 */

	if (!rb->aux_overwrite) {

	if (!rb->aux_overwrite) {

		aux_tail = ACCESS_ONCE(rb->user_page->aux_tail);

		aux_tail = ACCESS_ONCE(rb->user_page->aux_tail);

		handle->wakeup = local_read(&rb->aux_wakeup) + rb->aux_watermark;

		if (aux_head - aux_tail < perf_aux_size(rb))

		if (aux_head - aux_tail < perf_aux_size(rb))

			handle->size = CIRC_SPACE(aux_head, aux_tail, perf_aux_size(rb));

			handle->size = CIRC_SPACE(aux_head, aux_tail, perf_aux_size(rb));
@@ -359,9 +360,12 @@ void perf_aux_output_end(struct perf_output_handle *handle, unsigned long size, 
		perf_event_aux_event(handle->event, aux_head, size, flags);

		perf_event_aux_event(handle->event, aux_head, size, flags);

	}

	}





	rb->user_page->aux_head = local_read(&rb->aux_head);

	aux_head = rb->user_page->aux_head = local_read(&rb->aux_head);





	if (aux_head - local_read(&rb->aux_wakeup) >= rb->aux_watermark) {

		perf_output_wakeup(handle);

		perf_output_wakeup(handle);

		local_add(rb->aux_watermark, &rb->aux_wakeup);

	}

	handle->event = NULL;

	handle->event = NULL;





	local_set(&rb->aux_nest, 0);

	local_set(&rb->aux_nest, 0);
@@ -383,6 +387,14 @@ int perf_aux_output_skip(struct perf_output_handle *handle, unsigned long size) 




	local_add(size, &rb->aux_head);

	local_add(size, &rb->aux_head);





	aux_head = rb->user_page->aux_head = local_read(&rb->aux_head);

	if (aux_head - local_read(&rb->aux_wakeup) >= rb->aux_watermark) {

		perf_output_wakeup(handle);

		local_add(rb->aux_watermark, &rb->aux_wakeup);

		handle->wakeup = local_read(&rb->aux_wakeup) +

				 rb->aux_watermark;

	}



	handle->head = aux_head;

	handle->head = aux_head;

	handle->size -= size;

	handle->size -= size;
@@ -433,7 +445,7 @@ static void rb_free_aux_page(struct ring_buffer *rb, int idx) 
}

}





int rb_alloc_aux(struct ring_buffer *rb, struct perf_event *event,

int rb_alloc_aux(struct ring_buffer *rb, struct perf_event *event,

		 pgoff_t pgoff, int nr_pages, int flags)

		 pgoff_t pgoff, int nr_pages, long watermark, int flags)

{

{

	bool overwrite = !(flags & RING_BUFFER_WRITABLE);

	bool overwrite = !(flags & RING_BUFFER_WRITABLE);

	int node = (event->cpu == -1) ? -1 : cpu_to_node(event->cpu);

	int node = (event->cpu == -1) ? -1 : cpu_to_node(event->cpu);
@@ -497,6 +509,10 @@ int rb_alloc_aux(struct ring_buffer *rb, struct perf_event *event, 
	atomic_set(&rb->aux_refcount, 1);

	atomic_set(&rb->aux_refcount, 1);





	rb->aux_overwrite = overwrite;

	rb->aux_overwrite = overwrite;

	rb->aux_watermark = watermark;



	if (!rb->aux_watermark && !rb->aux_overwrite)

		rb->aux_watermark = nr_pages << (PAGE_SHIFT - 1);





out:

out:

	if (!ret)

	if (!ret)