Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752296AbbD0Etl (ORCPT ); Mon, 27 Apr 2015 00:49:41 -0400 Received: from mga02.intel.com ([134.134.136.20]:37866 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751744AbbD0Eth (ORCPT ); Mon, 27 Apr 2015 00:49:37 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.11,655,1422950400"; d="scan'208";a="701254952" From: Yuanhan Liu To: neilb@suse.de Cc: linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org, Yuanhan Liu , Ingo Molnar , Peter Zijlstra Subject: [PATCH 1/3] wait: introduce wait_event_cmd_exclusive Date: Mon, 27 Apr 2015 12:51:01 +0800 Message-Id: <1430110263-23977-1-git-send-email-yuanhan.liu@linux.intel.com> X-Mailer: git-send-email 1.9.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2044 Lines: 60 It's just a variant of wait_event_cmd, with exclusive flag being set. For cases like RAID5, which puts many processes to sleep until 1/4 resources are free, a wake_up wakes up all processes to run, but there is one process being able to get the resource as it's protected by a spin lock. That ends up introducing heavy lock contentions, and hurts performance badly. Here introduce wait_event_cmd_exclusive to relieve the lock contention naturally by letting wake_up() just wake up one process. Cc: Ingo Molnar Cc: Peter Zijlstra Signed-off-by: Yuanhan Liu --- include/linux/wait.h | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/include/linux/wait.h b/include/linux/wait.h index 2db8334..6c3b4de 100644 --- a/include/linux/wait.h +++ b/include/linux/wait.h @@ -358,10 +358,18 @@ do { \ __ret; \ }) -#define __wait_event_cmd(wq, condition, cmd1, cmd2) \ - (void)___wait_event(wq, condition, TASK_UNINTERRUPTIBLE, 0, 0, \ +#define __wait_event_cmd(wq, condition, cmd1, cmd2, exclusive) \ + (void)___wait_event(wq, condition, TASK_UNINTERRUPTIBLE, exclusive, 0, \ cmd1; schedule(); cmd2) + +#define wait_event_cmd_exclusive(wq, condition, cmd1, cmd2) \ +do { \ + if (condition) \ + break; \ + __wait_event_cmd(wq, condition, cmd1, cmd2, 1); \ +} while (0) + /** * wait_event_cmd - sleep until a condition gets true * @wq: the waitqueue to wait on @@ -380,7 +388,7 @@ do { \ do { \ if (condition) \ break; \ - __wait_event_cmd(wq, condition, cmd1, cmd2); \ + __wait_event_cmd(wq, condition, cmd1, cmd2, 0); \ } while (0) #define __wait_event_interruptible(wq, condition) \ -- 1.9.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/