From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756578Ab0JUBlr (ORCPT ); Wed, 20 Oct 2010 21:41:47 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.123]:51311 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753749Ab0JUBlp (ORCPT ); Wed, 20 Oct 2010 21:41:45 -0400 X-Authority-Analysis: v=1.1 cv=NFUeGz0loTdi/T6hXKngYYtckjed7x3pKvNOqmBBK18= c=1 sm=0 a=2_Pmyx3PJ40A:10 a=bbbx4UPp9XUA:10 a=OPBmh+XkhLl+Enan7BmTLg==:17 a=20KFwNOVAAAA:8 a=meVymXHHAAAA:8 a=WuZ4ZFVFXnlC1iJpLo4A:9 a=u7klmoz3noR3SwJhM3-dfs1FW0cA:4 a=jEp0ucaQiEUA:10 a=jeBq3FmKZ4MA:10 a=JbYq4k0lO0tzsvLY:21 a=efMSToZSwOiIxC0E:21 a=OPBmh+XkhLl+Enan7BmTLg==:117 X-Cloudmark-Score: 0 X-Originating-IP: 67.242.120.143 Message-Id: <20101021014142.692298333@goodmis.org> User-Agent: quilt/0.48-1 Date: Wed, 20 Oct 2010 21:39:07 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Andrew Morton , Thomas Gleixner , Frederic Weisbecker Subject: [PATCH v2 1/8] ring-buffer: Make write slow path out of line References: <20101021013906.507064528@goodmis.org> Content-Disposition: inline; filename=0001-ring-buffer-Make-write-slow-path-out-of-line.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Steven Rostedt Gcc inlines the slow path of the ring buffer write which can hurt performance. This patch simply forces the slow path function rb_move_tail() to always be a function. The ring_buffer_benchmark module with reader_disabled=1 shows that this patch changes the time to record an event from 135 ns to 132 ns. (3 ns or 2.22% improvement) Signed-off-by: Steven Rostedt --- kernel/trace/ring_buffer.c | 7 +++++-- 1 files changed, 5 insertions(+), 2 deletions(-) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index bca9637..0b88df8 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -1823,7 +1823,10 @@ 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) @@ -1943,7 +1946,7 @@ __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); -- 1.7.1