From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx122.postini.com [74.125.245.122]) by kanga.kvack.org (Postfix) with SMTP id 64FA06B004D for ; Sun, 1 Jan 2012 11:50:39 -0500 (EST) Message-ID: <4F008ECA.5040703@redhat.com> Date: Sun, 01 Jan 2012 18:50:18 +0200 From: Avi Kivity MIME-Version: 1.0 Subject: Re: [PATCH v4 4/5] slub: Only IPI CPUs that have per cpu obj to flush References: <1321960128-15191-1-git-send-email-gilad@benyossef.com> <1321960128-15191-5-git-send-email-gilad@benyossef.com> <4F00547A.9090204@redhat.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Gilad Ben-Yossef Cc: Pekka Enberg , linux-kernel@vger.kernel.org, Chris Metcalf , Peter Zijlstra , Frederic Weisbecker , Russell King , linux-mm@kvack.org, Matt Mackall , Sasha Levin , Rik van Riel , Andi Kleen , apkm@linux-foundation.org On 01/01/2012 06:12 PM, Gilad Ben-Yossef wrote: > > > > Since this seems to be a common pattern, how about: > > > > zalloc_cpumask_var_or_all_online_cpus(&cpus, GFTP_ATOMIC); > > ... > > free_cpumask_var(cpus); > > > > The long-named function at the top of the block either returns a newly > > allocated zeroed cpumask, or a static cpumask with all online cpus set. > > The code in the middle is only allowed to set bits in the cpumask > > (should be the common usage). free_cpumask_var() needs to check whether > > the freed object is the static variable. > > Thanks for the feedback and advice! I totally agree the repeating > pattern needs abstracting. > > I ended up chosing to try a different abstraction though - basically a wrapper > on_each_cpu_cond that gets a predicate function to run per CPU to > build the mask > to send the IPI to. It seems cleaner to me not having to mess with > free_cpumask_var > and it abstracts more of the general pattern. > This converts the algorithm to O(NR_CPUS) from a potentially lower complexity algorithm. Also, the existing algorithm may not like to be driven by cpu number. Both are true for kvm. -- error compiling committee.c: too many arguments to function -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org