From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752619AbbC0LLs (ORCPT ); Fri, 27 Mar 2015 07:11:48 -0400 Received: from resqmta-ch2-07v.sys.comcast.net ([69.252.207.39]:57781 "EHLO resqmta-ch2-07v.sys.comcast.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752235AbbC0LLr (ORCPT ); Fri, 27 Mar 2015 07:11:47 -0400 Date: Fri, 27 Mar 2015 06:11:44 -0500 (CDT) From: Christoph Lameter X-X-Sender: cl@gentwo.org To: Peter Zijlstra cc: Viresh Kumar , Andrew Morton , hannes@cmpxchg.org, Linaro Kernel Mailman List , Linux Kernel Mailing List , vinmenon@codeaurora.org, shashim@codeaurora.org, Michal Hocko , mgorman@suse.de, dave@stgolabs.net, koct9i@gmail.com, Linux Memory Management List , Suresh Siddha , Thomas Gleixner Subject: Re: [RFC] vmstat: Avoid waking up idle-cpu to service shepherd work In-Reply-To: <20150327093023.GA32047@worktop.ger.corp.intel.com> Message-ID: References: <359c926bc85cdf79650e39f2344c2083002545bb.1427347966.git.viresh.kumar@linaro.org> <20150326131822.fce6609efdd85b89ceb3f61c@linux-foundation.org> <20150327091613.GE27490@worktop.programming.kicks-ass.net> <20150327093023.GA32047@worktop.ger.corp.intel.com> Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 27 Mar 2015, Peter Zijlstra wrote: > > We could align the base on 8 bytes to gain an extra bit in the pointer > > and use that bit to indicate the running state. Then these sites can > > spin on that bit while we can change the actual base pointer. > > Even though tvec_base has ____cacheline_aligned stuck on, most are > allocated using kzalloc_node() which does not actually respect that but > already guarantees a minimum u64 alignment, so I think we can use that > third bit without too much magic. Create a new slab cache for this purpose that does the proper aligning?