From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752351Ab2AZKDW (ORCPT ); Thu, 26 Jan 2012 05:03:22 -0500 Received: from mail-ey0-f174.google.com ([209.85.215.174]:57241 "EHLO mail-ey0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752269Ab2AZKDQ (ORCPT ); Thu, 26 Jan 2012 05:03:16 -0500 From: Gilad Ben-Yossef To: linux-kernel@vger.kernel.org Cc: Gilad Ben-Yossef , Christoph Lameter , Chris Metcalf , Peter Zijlstra , Frederic Weisbecker , Russell King , linux-mm@kvack.org, Pekka Enberg , Matt Mackall , Sasha Levin , Rik van Riel , Andi Kleen , Mel Gorman , Andrew Morton , Alexander Viro , linux-fsdevel@vger.kernel.org, Avi Kivity , Michal Nazarewicz , Kosaki Motohiro , Milton Miller Subject: [v7 5/8] slub: only IPI CPUs that have per cpu obj to flush Date: Thu, 26 Jan 2012 12:01:58 +0200 Message-Id: <1327572121-13673-6-git-send-email-gilad@benyossef.com> X-Mailer: git-send-email 1.7.0.4 In-Reply-To: <1327572121-13673-1-git-send-email-gilad@benyossef.com> References: <1327572121-13673-1-git-send-email-gilad@benyossef.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org flush_all() is called for each kmem_cahce_destroy(). So every cache being destroyed dynamically ends up sending an IPI to each CPU in the system, regardless if the cache has ever been used there. For example, if you close the Infinband ipath driver char device file, the close file ops calls kmem_cache_destroy(). So running some infiniband config tool on one a single CPU dedicated to system tasks might interrupt the rest of the 127 CPUs dedicated to some CPU intensive or latency sensitive task. I suspect there is a good chance that every line in the output of "git grep kmem_cache_destroy linux/ | grep '\->'" has a similar scenario. This patch attempts to rectify this issue by sending an IPI to flush the per cpu objects back to the free lists only to CPUs that seem to have such objects. The check which CPU to IPI is racy but we don't care since asking a CPU without per cpu objects to flush does no damage and as far as I can tell the flush_all by itself is racy against allocs on remote CPUs anyway, so if you required the flush_all to be determinstic, you had to arrange for locking regardless. Without this patch the following artificial test case: $ cd /sys/kernel/slab $ for DIR in *; do cat $DIR/alloc_calls > /dev/null; done produces 166 IPIs on an cpuset isolated CPU. With it it produces none. The code path of memory allocation failure for CPUMASK_OFFSTACK=y config was tested using fault injection framework. Signed-off-by: Gilad Ben-Yossef CC: Christoph Lameter CC: Chris Metcalf CC: Peter Zijlstra CC: Frederic Weisbecker CC: Russell King CC: linux-mm@kvack.org CC: Pekka Enberg CC: Matt Mackall CC: Sasha Levin CC: Rik van Riel CC: Andi Kleen CC: Mel Gorman CC: Andrew Morton CC: Alexander Viro CC: linux-fsdevel@vger.kernel.org CC: Avi Kivity CC: Michal Nazarewicz CC: Kosaki Motohiro CC: Milton Miller --- mm/slub.c | 10 +++++++++- 1 files changed, 9 insertions(+), 1 deletions(-) diff --git a/mm/slub.c b/mm/slub.c index 4907563..3d75f89 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -2018,9 +2018,17 @@ static void flush_cpu_slab(void *d) __flush_cpu_slab(s, smp_processor_id()); } +static bool has_cpu_slab(int cpu, void *info) +{ + struct kmem_cache *s = info; + struct kmem_cache_cpu *c = per_cpu_ptr(s->cpu_slab, cpu); + + return !!(c->page); +} + static void flush_all(struct kmem_cache *s) { - on_each_cpu(flush_cpu_slab, s, 1); + on_each_cpu_cond(has_cpu_slab, flush_cpu_slab, s, 1, GFP_ATOMIC); } /* -- 1.7.0.4