From: Steven Rostedt (VMware) <rostedt@goodmis.org>
Date: Tue, 30 Jun 2020 13:04:35 +0000 (-0400)
Subject: ring-buffer: Mark the !tail (crossing a page) as unlikely
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=75b21c6dfa2d816bcabac24a530d9cffc12092b8;p=linux.git

ring-buffer: Mark the !tail (crossing a page) as unlikely

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>
---

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index ed1941304f698..888bc91779372 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 */