[for-next][PATCH 14/18] ring-buffer: Mark the !tail (crossing a page) as unlikely

Steven Rostedt
2020-07-02T21:58:53Z

It is the uncommon case where an event crosses a sub buffer boundary (page)
mark that check at the end of reserving an event as unlikely.

Suggested-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
kernel/trace/ring_buffer.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index ed1941304f69..888bc9177937 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -3260,7 +3260,7 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
* If this is the first commit on the page, then update
* its timestamp.
*/
- if (!tail)
+ if (unlikely(!tail))
tail_page->page->time_stamp = info->ts;

/* account for these added bytes */
--
2.26.2