From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751775Ab2AUGTg (ORCPT ); Sat, 21 Jan 2012 01:19:36 -0500 Received: from mga09.intel.com ([134.134.136.24]:4472 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751019Ab2AUGTc (ORCPT ); Sat, 21 Jan 2012 01:19:32 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.67,351,1309762800"; d="scan'208";a="101126956" Message-ID: <1327126770.7922.34.camel@yhuang-dev> Subject: Re: x86, mce, Use user return notifier in mce From: Huang Ying To: Tejun Heo Cc: Tony Luck , linux-kernel@vger.kernel.org, Ingo Molnar , Borislav Petkov , Chen Gong , Hidetoshi Seto Date: Sat, 21 Jan 2012 14:19:30 +0800 In-Reply-To: References: <1326415001-2145-1-git-send-email-ying.huang@intel.com> <1326436352.8294.22.camel@yhuang-dev> <1326676875.8294.30.camel@yhuang-dev> <20120120173427.GC3336@dhcp-172-17-108-109.mtv.corp.google.com> <1327113843.7922.27.camel@yhuang-dev> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.2-1 Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2012-01-20 at 21:56 -0800, Tejun Heo wrote: > Hello, > > On Fri, Jan 20, 2012 at 6:44 PM, Huang Ying wrote: > > It appears that WQ_HIGHPRI only provides priority between work queue, > > not between the work queue backing kthread and other tasks. Is there > > any mechanism for that? > > No, it doesn't. > > > If my understanding was correct, WQ_MEM_RECLAIM has some side-effect for > > that. Because hardware errors occurs seldom, the reserved kthread for > > WQ_MEME_RECLAIM just sleeps most of the time. When first hardware error > > occurs and the work item is queued, the reserved kthread is waked up. > > Because the reserved kthread sleeps for long time, it is highly possible > > for it to be scheduled at the next schedule point. > > But rescuer is used only under memory pressure. It doesn't help latency at all. > > > Because hardware error usually has no locality, WQ_UNBOUND can be used > > for it so that the work item can be put on relative low-load CPU. From > > the document, it is said WQ_UNBOUND work items will be executed ASAP > > too. Compared with WQ_HIGHPRI, how about the priority of WQ_UNBOUND? > > Maybe, maybe not. I suggest just using WQ_HIGHPRI for now and worrying > about it later if the scheduling latency actually turns out to matter. This is a performance issue. So maybe we need to measure the actual latency firstly. The first step can be using WQ_HIGHPRI as you suggested. Thanks for your information! Best Regards, Huang Ying