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authorIngo Molnar <mingo@elte.hu>2010-10-26 13:14:02 +0200
committerIngo Molnar <mingo@elte.hu>2010-10-26 13:14:02 +0200
commit5c16d2c813a7490408e966f52b881e70fc8d7f77 (patch)
tree3a2a4286a674d2e009f84687b5d0b74809774c28 /kernel
parent5df414c61e1b6f15bdc3759f292c7404286c9827 (diff)
parentb8b2663bd7c9da04ac804659b9f617c199d0252c (diff)
Merge branch 'tip/perf/ringbuffer-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace into perf/urgent
Diffstat (limited to 'kernel')
-rw-r--r--kernel/trace/ring_buffer.c335
1 files changed, 172 insertions, 163 deletions
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index c5a632a669e1..ec5c71005c14 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -224,6 +224,9 @@ enum {
RB_LEN_TIME_STAMP = 16,
};
+#define skip_time_extend(event) \
+ ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
+
static inline int rb_null_event(struct ring_buffer_event *event)
{
return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
@@ -248,8 +251,12 @@ rb_event_data_length(struct ring_buffer_event *event)
return length + RB_EVNT_HDR_SIZE;
}
-/* inline for ring buffer fast paths */
-static unsigned
+/*
+ * Return the length of the given event. Will return
+ * the length of the time extend if the event is a
+ * time extend.
+ */
+static inline unsigned
rb_event_length(struct ring_buffer_event *event)
{
switch (event->type_len) {
@@ -274,13 +281,41 @@ rb_event_length(struct ring_buffer_event *event)
return 0;
}
+/*
+ * Return total length of time extend and data,
+ * or just the event length for all other events.
+ */
+static inline unsigned
+rb_event_ts_length(struct ring_buffer_event *event)
+{
+ unsigned len = 0;
+
+ if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) {
+ /* time extends include the data event after it */
+ len = RB_LEN_TIME_EXTEND;
+ event = skip_time_extend(event);
+ }
+ return len + rb_event_length(event);
+}
+
/**
* ring_buffer_event_length - return the length of the event
* @event: the event to get the length of
+ *
+ * Returns the size of the data load of a data event.
+ * If the event is something other than a data event, it
+ * returns the size of the event itself. With the exception
+ * of a TIME EXTEND, where it still returns the size of the
+ * data load of the data event after it.
*/
unsigned ring_buffer_event_length(struct ring_buffer_event *event)
{
- unsigned length = rb_event_length(event);
+ unsigned length;
+
+ if (event->type_len == RINGBUF_TYPE_TIME_EXTEND)
+ event = skip_time_extend(event);
+
+ length = rb_event_length(event);
if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
return length;
length -= RB_EVNT_HDR_SIZE;
@@ -294,6 +329,8 @@ EXPORT_SYMBOL_GPL(ring_buffer_event_length);
static void *
rb_event_data(struct ring_buffer_event *event)
{
+ if (event->type_len == RINGBUF_TYPE_TIME_EXTEND)
+ event = skip_time_extend(event);
BUG_ON(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
/* If length is in len field, then array[0] has the data */
if (event->type_len)
@@ -404,9 +441,6 @@ static inline int test_time_stamp(u64 delta)
/* Max payload is BUF_PAGE_SIZE - header (8bytes) */
#define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
-/* Max number of timestamps that can fit on a page */
-#define RB_TIMESTAMPS_PER_PAGE (BUF_PAGE_SIZE / RB_LEN_TIME_EXTEND)
-
int ring_buffer_print_page_header(struct trace_seq *s)
{
struct buffer_data_page field;
@@ -1546,6 +1580,25 @@ static void rb_inc_iter(struct ring_buffer_iter *iter)
iter->head = 0;
}
+/* Slow path, do not inline */
+static noinline struct ring_buffer_event *
+rb_add_time_stamp(struct ring_buffer_event *event, u64 delta)
+{
+ event->type_len = RINGBUF_TYPE_TIME_EXTEND;
+
+ /* Not the first event on the page? */
+ if (rb_event_index(event)) {
+ event->time_delta = delta & TS_MASK;
+ event->array[0] = delta >> TS_SHIFT;
+ } else {
+ /* nope, just zero it */
+ event->time_delta = 0;
+ event->array[0] = 0;
+ }
+
+ return skip_time_extend(event);
+}
+
/**
* ring_buffer_update_event - update event type and data
* @event: the even to update
@@ -1558,28 +1611,31 @@ static void rb_inc_iter(struct ring_buffer_iter *iter)
* data field.
*/
static void
-rb_update_event(struct ring_buffer_event *event,
- unsigned type, unsigned length)
+rb_update_event(struct ring_buffer_per_cpu *cpu_buffer,
+ struct ring_buffer_event *event, unsigned length,
+ int add_timestamp, u64 delta)
{
- event->type_len = type;
-
- switch (type) {
-
- case RINGBUF_TYPE_PADDING:
- case RINGBUF_TYPE_TIME_EXTEND:
- case RINGBUF_TYPE_TIME_STAMP:
- break;
+ /* Only a commit updates the timestamp */
+ if (unlikely(!rb_event_is_commit(cpu_buffer, event)))
+ delta = 0;
- case 0:
- length -= RB_EVNT_HDR_SIZE;
- if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT)
- event->array[0] = length;
- else
- event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
- break;
- default:
- BUG();
+ /*
+ * If we need to add a timestamp, then we
+ * add it to the start of the resevered space.
+ */
+ if (unlikely(add_timestamp)) {
+ event = rb_add_time_stamp(event, delta);
+ length -= RB_LEN_TIME_EXTEND;
+ delta = 0;
}
+
+ event->time_delta = delta;
+ length -= RB_EVNT_HDR_SIZE;
+ if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) {
+ event->type_len = 0;
+ event->array[0] = length;
+ } else
+ event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
}
/*
@@ -1823,10 +1879,13 @@ rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
local_sub(length, &tail_page->write);
}
-static struct ring_buffer_event *
+/*
+ * This is the slow path, force gcc not to inline it.
+ */
+static noinline struct ring_buffer_event *
rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
unsigned long length, unsigned long tail,
- struct buffer_page *tail_page, u64 *ts)
+ struct buffer_page *tail_page, u64 ts)
{
struct buffer_page *commit_page = cpu_buffer->commit_page;
struct ring_buffer *buffer = cpu_buffer->buffer;
@@ -1909,8 +1968,8 @@ rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
* Nested commits always have zero deltas, so
* just reread the time stamp
*/
- *ts = rb_time_stamp(buffer);
- next_page->page->time_stamp = *ts;
+ ts = rb_time_stamp(buffer);
+ next_page->page->time_stamp = ts;
}
out_again:
@@ -1929,12 +1988,21 @@ rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
static struct ring_buffer_event *
__rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
- unsigned type, unsigned long length, u64 *ts)
+ unsigned long length, u64 ts,
+ u64 delta, int add_timestamp)
{
struct buffer_page *tail_page;
struct ring_buffer_event *event;
unsigned long tail, write;
+ /*
+ * If the time delta since the last event is too big to
+ * hold in the time field of the event, then we append a
+ * TIME EXTEND event ahead of the data event.
+ */
+ if (unlikely(add_timestamp))
+ length += RB_LEN_TIME_EXTEND;
+
tail_page = cpu_buffer->tail_page;
write = local_add_return(length, &tail_page->write);
@@ -1943,7 +2011,7 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
tail = write - length;
/* See if we shot pass the end of this buffer page */
- if (write > BUF_PAGE_SIZE)
+ if (unlikely(write > BUF_PAGE_SIZE))
return rb_move_tail(cpu_buffer, length, tail,
tail_page, ts);
@@ -1951,18 +2019,16 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
event = __rb_page_index(tail_page, tail);
kmemcheck_annotate_bitfield(event, bitfield);
- rb_update_event(event, type, length);
+ rb_update_event(cpu_buffer, event, length, add_timestamp, delta);
- /* The passed in type is zero for DATA */
- if (likely(!type))
- local_inc(&tail_page->entries);
+ local_inc(&tail_page->entries);
/*
* If this is the first commit on the page, then update
* its timestamp.
*/
if (!tail)
- tail_page->page->time_stamp = *ts;
+ tail_page->page->time_stamp = ts;
return event;
}
@@ -1977,7 +2043,7 @@ rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
unsigned long addr;
new_index = rb_event_index(event);
- old_index = new_index + rb_event_length(event);
+ old_index = new_index + rb_event_ts_length(event);
addr = (unsigned long)event;
addr &= PAGE_MASK;
@@ -2003,76 +2069,13 @@ rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
return 0;
}
-static int
-rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer,
- u64 *ts, u64 *delta)
-{
- struct ring_buffer_event *event;
- int ret;
-
- WARN_ONCE(*delta > (1ULL << 59),
- KERN_WARNING "Delta way too big! %llu ts=%llu write stamp = %llu\n",
- (unsigned long long)*delta,
- (unsigned long long)*ts,
- (unsigned long long)cpu_buffer->write_stamp);
-
- /*
- * The delta is too big, we to add a
- * new timestamp.
- */
- event = __rb_reserve_next(cpu_buffer,
- RINGBUF_TYPE_TIME_EXTEND,
- RB_LEN_TIME_EXTEND,
- ts);
- if (!event)
- return -EBUSY;
-
- if (PTR_ERR(event) == -EAGAIN)
- return -EAGAIN;
-
- /* Only a commited time event can update the write stamp */
- if (rb_event_is_commit(cpu_buffer, event)) {
- /*
- * If this is the first on the page, then it was
- * updated with the page itself. Try to discard it
- * and if we can't just make it zero.
- */
- if (rb_event_index(event)) {
- event->time_delta = *delta & TS_MASK;
- event->array[0] = *delta >> TS_SHIFT;
- } else {
- /* try to discard, since we do not need this */
- if (!rb_try_to_discard(cpu_buffer, event)) {
- /* nope, just zero it */
- event->time_delta = 0;
- event->array[0] = 0;
- }
- }
- cpu_buffer->write_stamp = *ts;
- /* let the caller know this was the commit */
- ret = 1;
- } else {
- /* Try to discard the event */
- if (!rb_try_to_discard(cpu_buffer, event)) {
- /* Darn, this is just wasted space */
- event->time_delta = 0;
- event->array[0] = 0;
- }
- ret = 0;
- }
-
- *delta = 0;
-
- return ret;
-}
-
static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
{
local_inc(&cpu_buffer->committing);
local_inc(&cpu_buffer->commits);
}
-static void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
+static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
{
unsigned long commits;
@@ -2110,9 +2113,10 @@ rb_reserve_next_event(struct ring_buffer *buffer,
unsigned long length)
{
struct ring_buffer_event *event;
- u64 ts, delta = 0;
- int commit = 0;
+ u64 ts, delta;
int nr_loops = 0;
+ int add_timestamp;
+ u64 diff;
rb_start_commit(cpu_buffer);
@@ -2133,6 +2137,9 @@ rb_reserve_next_event(struct ring_buffer *buffer,
length = rb_calculate_event_length(length);
again:
+ add_timestamp = 0;
+ delta = 0;
+
/*
* We allow for interrupts to reenter here and do a trace.
* If one does, it will cause this original code to loop
@@ -2146,56 +2153,32 @@ rb_reserve_next_event(struct ring_buffer *buffer,
goto out_fail;
ts = rb_time_stamp(cpu_buffer->buffer);
+ diff = ts - cpu_buffer->write_stamp;
- /*
- * Only the first commit can update the timestamp.
- * Yes there is a race here. If an interrupt comes in
- * just after the conditional and it traces too, then it
- * will also check the deltas. More than one timestamp may
- * also be made. But only the entry that did the actual
- * commit will be something other than zero.
- */
- if (likely(cpu_buffer->tail_page == cpu_buffer->commit_page &&
- rb_page_write(cpu_buffer->tail_page) ==
- rb_commit_index(cpu_buffer))) {
- u64 diff;
-
- diff = ts - cpu_buffer->write_stamp;
-
- /* make sure this diff is calculated here */
- barrier();
-
- /* Did the write stamp get updated already? */
- if (unlikely(ts < cpu_buffer->write_stamp))
- goto get_event;
+ /* make sure this diff is calculated here */
+ barrier();
+ /* Did the write stamp get updated already? */
+ if (likely(ts >= cpu_buffer->write_stamp)) {
delta = diff;
if (unlikely(test_time_stamp(delta))) {
-
- commit = rb_add_time_stamp(cpu_buffer, &ts, &delta);
- if (commit == -EBUSY)
- goto out_fail;
-
- if (commit == -EAGAIN)
- goto again;
-
- RB_WARN_ON(cpu_buffer, commit < 0);
+ WARN_ONCE(delta > (1ULL << 59),
+ KERN_WARNING "Delta way too big! %llu ts=%llu write stamp = %llu\n",
+ (unsigned long long)delta,
+ (unsigned long long)ts,
+ (unsigned long long)cpu_buffer->write_stamp);
+ add_timestamp = 1;
}
}
- get_event:
- event = __rb_reserve_next(cpu_buffer, 0, length, &ts);
+ event = __rb_reserve_next(cpu_buffer, length, ts,
+ delta, add_timestamp);
if (unlikely(PTR_ERR(event) == -EAGAIN))
goto again;
if (!event)
goto out_fail;
- if (!rb_event_is_commit(cpu_buffer, event))
- delta = 0;
-
- event->time_delta = delta;
-
return event;
out_fail:
@@ -2207,13 +2190,9 @@ rb_reserve_next_event(struct ring_buffer *buffer,
#define TRACE_RECURSIVE_DEPTH 16
-static int trace_recursive_lock(void)
+/* Keep this code out of the fast path cache */
+static noinline void trace_recursive_fail(void)
{
- current->trace_recursion++;
-
- if (likely(current->trace_recursion < TRACE_RECURSIVE_DEPTH))
- return 0;
-
/* Disable all tracing before we do anything else */
tracing_off_permanent();
@@ -2225,10 +2204,21 @@ static int trace_recursive_lock(void)
in_nmi());
WARN_ON_ONCE(1);
+}
+
+static inline int trace_recursive_lock(void)
+{
+ current->trace_recursion++;
+
+ if (likely(current->trace_recursion < TRACE_RECURSIVE_DEPTH))
+ return 0;
+
+ trace_recursive_fail();
+
return -1;
}
-static void trace_recursive_unlock(void)
+static inline void trace_recursive_unlock(void)
{
WARN_ON_ONCE(!current->trace_recursion);
@@ -2308,12 +2298,28 @@ static void
rb_update_write_stamp(struct ring_buffer_per_cpu *cpu_buffer,
struct ring_buffer_event *event)
{
+ u64 delta;
+
/*
* The event first in the commit queue updates the
* time stamp.
*/
- if (rb_event_is_commit(cpu_buffer, event))
- cpu_buffer->write_stamp += event->time_delta;
+ if (rb_event_is_commit(cpu_buffer, event)) {
+ /*
+ * A commit event that is first on a page
+ * updates the write timestamp with the page stamp
+ */
+ if (!rb_event_index(event))
+ cpu_buffer->write_stamp =
+ cpu_buffer->commit_page->page->time_stamp;
+ else if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) {
+ delta = event->array[0];
+ delta <<= TS_SHIFT;
+ delta += event->time_delta;
+ cpu_buffer->write_stamp += delta;
+ } else
+ cpu_buffer->write_stamp += event->time_delta;
+ }
}
static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
@@ -2353,6 +2359,9 @@ EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
static inline void rb_event_discard(struct ring_buffer_event *event)
{
+ if (event->type_len == RINGBUF_TYPE_TIME_EXTEND)
+ event = skip_time_extend(event);
+
/* array[0] holds the actual length for the discarded event */
event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
event->type_len = RINGBUF_TYPE_PADDING;
@@ -3049,12 +3058,12 @@ rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts,
again:
/*
- * We repeat when a timestamp is encountered. It is possible
- * to get multiple timestamps from an interrupt entering just
- * as one timestamp is about to be written, or from discarded
- * commits. The most that we can have is the number on a single page.
+ * We repeat when a time extend is encountered.
+ * Since the time extend is always attached to a data event,
+ * we should never loop more than once.
+ * (We never hit the following condition more than twice).
*/
- if (RB_WARN_ON(cpu_buffer, ++nr_loops > RB_TIMESTAMPS_PER_PAGE))
+ if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
return NULL;
reader = rb_get_reader_page(cpu_buffer);
@@ -3130,14 +3139,12 @@ rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
return NULL;
/*
- * We repeat when a timestamp is encountered.
- * We can get multiple timestamps by nested interrupts or also
- * if filtering is on (discarding commits). Since discarding
- * commits can be frequent we can get a lot of timestamps.
- * But we limit them by not adding timestamps if they begin
- * at the start of a page.
+ * We repeat when a time extend is encountered.
+ * Since the time extend is always attached to a data event,
+ * we should never loop more than once.
+ * (We never hit the following condition more than twice).
*/
- if (RB_WARN_ON(cpu_buffer, ++nr_loops > RB_TIMESTAMPS_PER_PAGE))
+ if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
return NULL;
if (rb_per_cpu_empty(cpu_buffer))
@@ -3835,7 +3842,8 @@ int ring_buffer_read_page(struct ring_buffer *buffer,
if (len > (commit - read))
len = (commit - read);
- size = rb_event_length(event);
+ /* Always keep the time extend and data together */
+ size = rb_event_ts_length(event);
if (len < size)
goto out_unlock;
@@ -3857,7 +3865,8 @@ int ring_buffer_read_page(struct ring_buffer *buffer,
break;
event = rb_reader_event(cpu_buffer);
- size = rb_event_length(event);
+ /* Always keep the time extend and data together */
+ size = rb_event_ts_length(event);
} while (len > size);
/* update bpage */

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