[tip:perf/core] perf: Simplify the ring-buffer logic: make perf_buffer_alloc() do everything needed

tip-bot for Peter Zijlstra
2010-06-09T10:17:15Z

Commit-ID: d57e34fdd60be7ffd0b1d86bfa1a553df86b7172
Gitweb: http://git.kernel.org/tip/d57e34fdd60be7ffd0b1d86bfa1a553df86b7172
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Fri, 28 May 2010 19:41:35 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Wed, 9 Jun 2010 11:12:35 +0200

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: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
include/linux/perf_event.h | 2 +
kernel/perf_event.c | 61 ++++++++++++++++++++++++-------------------
2 files changed, 36 insertions(+), 27 deletions(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 2a0da02..441992a 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -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;
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 93d5458..f75c9c9 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -2369,6 +2369,25 @@ unlock:
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 @@ unlock:
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;