Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751386AbaBMOFb (ORCPT ); Thu, 13 Feb 2014 09:05:31 -0500 Received: from mail-wi0-f180.google.com ([209.85.212.180]:64096 "EHLO mail-wi0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750839AbaBMOF3 (ORCPT ); Thu, 13 Feb 2014 09:05:29 -0500 Date: Thu, 13 Feb 2014 15:05:25 +0100 From: Frederic Weisbecker To: "Paul E. McKenney" Cc: Tejun Heo , Kevin Hilman , Lai Jiangshan , Zoran Markovic , linux-kernel@vger.kernel.org, Shaibal Dutta , Dipankar Sarma Subject: Re: [RFC PATCH] rcu: move SRCU grace period work to power efficient workqueue Message-ID: <20140213140523.GB14383@localhost.localdomain> References: <1391197986-12774-1-git-send-email-zoran.markovic@linaro.org> <52F8A51F.4090909@cn.fujitsu.com> <20140210184729.GL4250@linux.vnet.ibm.com> <20140212182336.GD5496@localhost.localdomain> <20140212190241.GD4250@linux.vnet.ibm.com> <20140212192354.GC26809@htj.dyndns.org> <20140212195922.GE4250@linux.vnet.ibm.com> <20140212230454.GA14383@localhost.localdomain> <20140213003311.GJ4250@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140213003311.GJ4250@linux.vnet.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 12, 2014 at 04:33:11PM -0800, Paul E. McKenney wrote: > > Fair point! I wordsmithed it into the following. Seem reasonable? > > Thanx, Paul > > ------------------------------------------------------------------------ > > Documentation/kernel-per-CPU-kthreads.txt: Workqueue affinity > > This commit documents the ability to apply CPU affinity to WQ_SYSFS > workqueues, thus offloading them from the desired worker CPUs. > > Signed-off-by: Paul E. McKenney > Reviewed-by: Tejun Heo > Acked-by: Frederic Weisbecker > > diff --git a/Documentation/kernel-per-CPU-kthreads.txt b/Documentation/kernel-per-CPU-kthreads.txt > index 827104fb9364..f3cd299fcc41 100644 > --- a/Documentation/kernel-per-CPU-kthreads.txt > +++ b/Documentation/kernel-per-CPU-kthreads.txt > @@ -162,7 +162,18 @@ Purpose: Execute workqueue requests > To reduce its OS jitter, do any of the following: > 1. Run your workload at a real-time priority, which will allow > preempting the kworker daemons. > -2. Do any of the following needed to avoid jitter that your > +2. A given workqueue can be made visible in the sysfs filesystem > + by passing the WQ_SYSFS to that workqueue's alloc_workqueue(). > + Such a workqueue can be confined to a given subset of the > + CPUs using the /sys/devices/virtual/workqueue/*/cpumask sysfs > + files. The set of WQ_SYSFS workqueues can be displayed using > + "ls sys/devices/virtual/workqueue". That said, the workqueues > + maintainer would like to caution people against indiscriminately > + sprinkling WQ_SYSFS across all the workqueues. The reason for > + caution is that it is easy to add WQ_SYSFS, but because sysfs is > + part of the formal user/kernel API, it can be nearly impossible > + to remove it, even if its addition was a mistake. > +3. Do any of the following needed to avoid jitter that your > application cannot tolerate: > a. Build your kernel with CONFIG_SLUB=y rather than > CONFIG_SLAB=y, thus avoiding the slab allocator's periodic > Perfect!! -- 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/