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-rw-r--r--kernel/trace/ring_buffer.c37
1 files changed, 21 insertions, 16 deletions
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 5092660..7102d7a 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -370,6 +370,9 @@ 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_STAMP)
+
int ring_buffer_print_page_header(struct trace_seq *s)
{
struct buffer_data_page field;
@@ -1409,8 +1412,12 @@ rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer,
event->array[0] = *delta >> TS_SHIFT;
} else {
cpu_buffer->commit_page->page->time_stamp = *ts;
- event->time_delta = 0;
- event->array[0] = 0;
+ /* 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 */
@@ -2268,8 +2275,8 @@ static void rb_advance_iter(struct ring_buffer_iter *iter)
* Check if we are at the end of the buffer.
*/
if (iter->head >= rb_page_size(iter->head_page)) {
- if (RB_WARN_ON(buffer,
- iter->head_page == cpu_buffer->commit_page))
+ /* discarded commits can make the page empty */
+ if (iter->head_page == cpu_buffer->commit_page)
return;
rb_inc_iter(iter);
return;
@@ -2312,12 +2319,10 @@ rb_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts)
/*
* 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. The max times
- * that this can happen is the number of nested interrupts we
- * can have. Nesting 10 deep of interrupts is clearly
- * an anomaly.
+ * 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.
*/
- if (RB_WARN_ON(cpu_buffer, ++nr_loops > 10))
+ if (RB_WARN_ON(cpu_buffer, ++nr_loops > RB_TIMESTAMPS_PER_PAGE))
return NULL;
reader = rb_get_reader_page(cpu_buffer);
@@ -2383,14 +2388,14 @@ rb_iter_peek(struct ring_buffer_iter *iter, 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. The max times
- * that this can happen is the number of nested interrupts we
- * can have. Nesting 10 deep of interrupts is clearly
- * an anomaly.
+ * 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.
*/
- if (RB_WARN_ON(cpu_buffer, ++nr_loops > 10))
+ if (RB_WARN_ON(cpu_buffer, ++nr_loops > RB_TIMESTAMPS_PER_PAGE))
return NULL;
if (rb_per_cpu_empty(cpu_buffer))
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