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yaml
---
r: 121237
b: refs/heads/master
c: abc9b56
h: refs/heads/master
i:
  121235: eea376f
v: v3
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Steven Rostedt authored and Ingo Molnar committed Dec 3, 2008
1 parent 1fd6c0e commit 1e7113d
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Showing 2 changed files with 37 additions and 28 deletions.
2 changes: 1 addition & 1 deletion [refs]
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Original file line number Diff line number Diff line change
@@ -1,2 +1,2 @@
---
refs/heads/master: a5e25883a445dce94a087ca479b21a5959cd5c18
refs/heads/master: abc9b56d66fbd4d93302ef4bf6fa726e1b8255f9
63 changes: 36 additions & 27 deletions trunk/kernel/trace/ring_buffer.c
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Original file line number Diff line number Diff line change
Expand Up @@ -195,20 +195,24 @@ void *ring_buffer_event_data(struct ring_buffer_event *event)
#define TS_MASK ((1ULL << TS_SHIFT) - 1)
#define TS_DELTA_TEST (~TS_MASK)

/*
* This hack stolen from mm/slob.c.
* We can store per page timing information in the page frame of the page.
* Thanks to Peter Zijlstra for suggesting this idea.
*/
struct buffer_page {
struct buffer_data_page {
u64 time_stamp; /* page time stamp */
local_t write; /* index for next write */
local_t commit; /* write commited index */
unsigned char data[]; /* data of buffer page */
};

struct buffer_page {
local_t write; /* index for next write */
unsigned read; /* index for next read */
struct list_head list; /* list of free pages */
void *page; /* Actual data page */
struct buffer_data_page *page; /* Actual data page */
};

static void rb_init_page(struct buffer_data_page *page)
{
local_set(&page->commit, 0);
}

/*
* Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
* this issue out.
Expand All @@ -230,7 +234,7 @@ static inline int test_time_stamp(u64 delta)
return 0;
}

#define BUF_PAGE_SIZE PAGE_SIZE
#define BUF_PAGE_SIZE (PAGE_SIZE - sizeof(struct buffer_data_page))

/*
* head_page == tail_page && head == tail then buffer is empty.
Expand Down Expand Up @@ -333,6 +337,7 @@ static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
if (!addr)
goto free_pages;
page->page = (void *)addr;
rb_init_page(page->page);
}

list_splice(&pages, head);
Expand Down Expand Up @@ -378,6 +383,7 @@ rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu)
if (!addr)
goto fail_free_reader;
page->page = (void *)addr;
rb_init_page(page->page);

INIT_LIST_HEAD(&cpu_buffer->reader_page->list);

Expand Down Expand Up @@ -647,6 +653,7 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
if (!addr)
goto free_pages;
page->page = (void *)addr;
rb_init_page(page->page);
}
}

Expand Down Expand Up @@ -682,7 +689,7 @@ static inline int rb_null_event(struct ring_buffer_event *event)

static inline void *__rb_page_index(struct buffer_page *page, unsigned index)
{
return page->page + index;
return page->page->data + index;
}

static inline struct ring_buffer_event *
Expand Down Expand Up @@ -712,7 +719,7 @@ static inline unsigned rb_page_write(struct buffer_page *bpage)

static inline unsigned rb_page_commit(struct buffer_page *bpage)
{
return local_read(&bpage->commit);
return local_read(&bpage->page->commit);
}

/* Size is determined by what has been commited */
Expand Down Expand Up @@ -804,14 +811,15 @@ rb_set_commit_event(struct ring_buffer_per_cpu *cpu_buffer,
if (RB_WARN_ON(cpu_buffer,
cpu_buffer->commit_page == cpu_buffer->tail_page))
return;
cpu_buffer->commit_page->commit =
cpu_buffer->commit_page->page->commit =
cpu_buffer->commit_page->write;
rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
cpu_buffer->write_stamp = cpu_buffer->commit_page->time_stamp;
cpu_buffer->write_stamp =
cpu_buffer->commit_page->page->time_stamp;
}

/* Now set the commit to the event's index */
local_set(&cpu_buffer->commit_page->commit, index);
local_set(&cpu_buffer->commit_page->page->commit, index);
}

static inline void
Expand All @@ -826,24 +834,25 @@ rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
* assign the commit to the tail.
*/
while (cpu_buffer->commit_page != cpu_buffer->tail_page) {
cpu_buffer->commit_page->commit =
cpu_buffer->commit_page->page->commit =
cpu_buffer->commit_page->write;
rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
cpu_buffer->write_stamp = cpu_buffer->commit_page->time_stamp;
cpu_buffer->write_stamp =
cpu_buffer->commit_page->page->time_stamp;
/* add barrier to keep gcc from optimizing too much */
barrier();
}
while (rb_commit_index(cpu_buffer) !=
rb_page_write(cpu_buffer->commit_page)) {
cpu_buffer->commit_page->commit =
cpu_buffer->commit_page->page->commit =
cpu_buffer->commit_page->write;
barrier();
}
}

static void rb_reset_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
{
cpu_buffer->read_stamp = cpu_buffer->reader_page->time_stamp;
cpu_buffer->read_stamp = cpu_buffer->reader_page->page->time_stamp;
cpu_buffer->reader_page->read = 0;
}

Expand All @@ -862,7 +871,7 @@ static inline void rb_inc_iter(struct ring_buffer_iter *iter)
else
rb_inc_page(cpu_buffer, &iter->head_page);

iter->read_stamp = iter->head_page->time_stamp;
iter->read_stamp = iter->head_page->page->time_stamp;
iter->head = 0;
}

Expand Down Expand Up @@ -998,12 +1007,12 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
*/
if (tail_page == cpu_buffer->tail_page) {
local_set(&next_page->write, 0);
local_set(&next_page->commit, 0);
local_set(&next_page->page->commit, 0);
cpu_buffer->tail_page = next_page;

/* reread the time stamp */
*ts = ring_buffer_time_stamp(cpu_buffer->cpu);
cpu_buffer->tail_page->time_stamp = *ts;
cpu_buffer->tail_page->page->time_stamp = *ts;
}

/*
Expand Down Expand Up @@ -1048,7 +1057,7 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
* this page's time stamp.
*/
if (!tail && rb_is_commit(cpu_buffer, event))
cpu_buffer->commit_page->time_stamp = *ts;
cpu_buffer->commit_page->page->time_stamp = *ts;

return event;

Expand Down Expand Up @@ -1099,7 +1108,7 @@ rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer,
event->time_delta = *delta & TS_MASK;
event->array[0] = *delta >> TS_SHIFT;
} else {
cpu_buffer->commit_page->time_stamp = *ts;
cpu_buffer->commit_page->page->time_stamp = *ts;
event->time_delta = 0;
event->array[0] = 0;
}
Expand Down Expand Up @@ -1552,7 +1561,7 @@ static void rb_iter_reset(struct ring_buffer_iter *iter)
if (iter->head)
iter->read_stamp = cpu_buffer->read_stamp;
else
iter->read_stamp = iter->head_page->time_stamp;
iter->read_stamp = iter->head_page->page->time_stamp;
}

/**
Expand Down Expand Up @@ -1696,7 +1705,7 @@ rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
cpu_buffer->reader_page->list.prev = reader->list.prev;

local_set(&cpu_buffer->reader_page->write, 0);
local_set(&cpu_buffer->reader_page->commit, 0);
local_set(&cpu_buffer->reader_page->page->commit, 0);

/* Make the reader page now replace the head */
reader->list.prev->next = &cpu_buffer->reader_page->list;
Expand Down Expand Up @@ -2088,7 +2097,7 @@ rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
cpu_buffer->head_page
= list_entry(cpu_buffer->pages.next, struct buffer_page, list);
local_set(&cpu_buffer->head_page->write, 0);
local_set(&cpu_buffer->head_page->commit, 0);
local_set(&cpu_buffer->head_page->page->commit, 0);

cpu_buffer->head_page->read = 0;

Expand All @@ -2097,7 +2106,7 @@ rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)

INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
local_set(&cpu_buffer->reader_page->write, 0);
local_set(&cpu_buffer->reader_page->commit, 0);
local_set(&cpu_buffer->reader_page->page->commit, 0);
cpu_buffer->reader_page->read = 0;

cpu_buffer->overrun = 0;
Expand Down

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