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Commit d57e34fd authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
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perf: Simplify the ring-buffer logic: make perf_buffer_alloc() do everything needed 



Currently there are perf_buffer_alloc() + perf_buffer_init() + some
separate bits, fold it all into a single perf_buffer_alloc() and only
leave the attachment to the event separate.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent ca5135e6

include/linux/perf_event.h

+2 −0
Original line number Diff line number Diff line
@@ -602,6 +602,8 @@ enum perf_event_active_state { 


struct file;



#define PERF_BUFFER_WRITABLE		0x01



struct perf_buffer {

	atomic_t			refcount;

	struct rcu_head			rcu_head;

kernel/perf_event.c

+34 −27
Original line number Diff line number Diff line
@@ -2369,6 +2369,25 @@ void perf_event_update_userpage(struct perf_event *event) 
	rcu_read_unlock();

}



static unsigned long perf_data_size(struct perf_buffer *buffer);



static void

perf_buffer_init(struct perf_buffer *buffer, long watermark, int flags)

{

	long max_size = perf_data_size(buffer);



	if (watermark)

		buffer->watermark = min(max_size, watermark);



	if (!buffer->watermark)

		buffer->watermark = max_size / 2;



	if (flags & PERF_BUFFER_WRITABLE)

		buffer->writable = 1;



	atomic_set(&buffer->refcount, 1);

}



#ifndef CONFIG_PERF_USE_VMALLOC



/*
@@ -2401,7 +2420,7 @@ static void *perf_mmap_alloc_page(int cpu) 
}



static struct perf_buffer *

perf_buffer_alloc(struct perf_event *event, int nr_pages)

perf_buffer_alloc(int nr_pages, long watermark, int cpu, int flags)

{

	struct perf_buffer *buffer;

	unsigned long size;
@@ -2414,18 +2433,20 @@ perf_buffer_alloc(struct perf_event *event, int nr_pages) 
	if (!buffer)

		goto fail;



	buffer->user_page = perf_mmap_alloc_page(event->cpu);

	buffer->user_page = perf_mmap_alloc_page(cpu);

	if (!buffer->user_page)

		goto fail_user_page;



	for (i = 0; i < nr_pages; i++) {

		buffer->data_pages[i] = perf_mmap_alloc_page(event->cpu);

		buffer->data_pages[i] = perf_mmap_alloc_page(cpu);

		if (!buffer->data_pages[i])

			goto fail_data_pages;

	}



	buffer->nr_pages = nr_pages;



	perf_buffer_init(buffer, watermark, flags);



	return buffer;



fail_data_pages:
@@ -2516,7 +2537,7 @@ static void perf_buffer_free(struct perf_buffer *buffer) 
}



static struct perf_buffer *

perf_buffer_alloc(struct perf_event *event, int nr_pages)

perf_buffer_alloc(int nr_pages, long watermark, int cpu, int flags)

{

	struct perf_buffer *buffer;

	unsigned long size;
@@ -2540,6 +2561,8 @@ perf_buffer_alloc(struct perf_event *event, int nr_pages) 
	buffer->page_order = ilog2(nr_pages);

	buffer->nr_pages = 1;



	perf_buffer_init(buffer, watermark, flags);



	return buffer;



fail_all_buf:
@@ -2591,23 +2614,6 @@ static int perf_mmap_fault(struct vm_area_struct *vma, struct vm_fault *vmf) 
	return ret;

}



static void

perf_buffer_init(struct perf_event *event, struct perf_buffer *buffer)

{

	long max_size = perf_data_size(buffer);



	if (event->attr.watermark) {

		buffer->watermark = min_t(long, max_size,

					event->attr.wakeup_watermark);

	}



	if (!buffer->watermark)

		buffer->watermark = max_size / 2;



	atomic_set(&buffer->refcount, 1);

	rcu_assign_pointer(event->buffer, buffer);

}



static void perf_buffer_free_rcu(struct rcu_head *rcu_head)

{

	struct perf_buffer *buffer;
@@ -2682,7 +2688,7 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma) 
	unsigned long vma_size;

	unsigned long nr_pages;

	long user_extra, extra;

	int ret = 0;

	int ret = 0, flags = 0;



	/*

	 * Don't allow mmap() of inherited per-task counters. This would
@@ -2747,15 +2753,16 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma) 


	WARN_ON(event->buffer);



	buffer = perf_buffer_alloc(event, nr_pages);

	if (vma->vm_flags & VM_WRITE)

		flags |= PERF_BUFFER_WRITABLE;



	buffer = perf_buffer_alloc(nr_pages, event->attr.wakeup_watermark,

				   event->cpu, flags);

	if (!buffer) {

		ret = -ENOMEM;

		goto unlock;

	}



	perf_buffer_init(event, buffer);

	if (vma->vm_flags & VM_WRITE)

		event->buffer->writable = 1;

	rcu_assign_pointer(event->buffer, buffer);



	atomic_long_add(user_extra, &user->locked_vm);

	event->mmap_locked = extra;