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 ed1941304f69809428ab79fd71f5607c7df6a562..888bc917793727f80695c976a6940f89fffa8dc7 100644 (file)
--- 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 */