From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752174Ab1LLERH (ORCPT ); Sun, 11 Dec 2011 23:17:07 -0500 Received: from mga03.intel.com ([143.182.124.21]:57065 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752020Ab1LLERD (ORCPT ); Sun, 11 Dec 2011 23:17:03 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.71,315,1320652800"; d="scan'208";a="84635495" Subject: Re: [PATCH 1/3] slub: set a criteria for slub node partial adding From: "Alex,Shi" To: "Li, Shaohua" Cc: David Rientjes , Christoph Lameter , "penberg@kernel.org" , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , Andi Kleen In-Reply-To: <1323657793.22361.383.camel@sli10-conroe> References: <1322814189-17318-1-git-send-email-alex.shi@intel.com> <1323076965.16790.670.camel@debian> <1323234673.22361.372.camel@sli10-conroe> <1323657793.22361.383.camel@sli10-conroe> Content-Type: text/plain; charset="UTF-8" Date: Mon, 12 Dec 2011 12:14:11 +0800 Message-ID: <1323663251.16790.6115.camel@debian> Mime-Version: 1.0 X-Mailer: Evolution 2.28.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2011-12-12 at 10:43 +0800, Li, Shaohua wrote: > On Wed, 2011-12-07 at 15:28 +0800, David Rientjes wrote: > > On Wed, 7 Dec 2011, Shaohua Li wrote: > > > > > interesting. I did similar experiment before (try to sort the page > > > according to free number), but it appears quite hard. The free number of > > > a page is dynamic, eg more slabs can be freed when the page is in > > > partial list. And in netperf test, the partial list could be very very > > > long. Can you post your patch, I definitely what to look at it. > > > > It was over a couple of years ago and the slub code has changed > > significantly since then, but you can see the general concept of the "slab > > thrashing" problem with netperf and my solution back then: > > > > http://marc.info/?l=linux-kernel&m=123839191416478 > > http://marc.info/?l=linux-kernel&m=123839203016592 > > http://marc.info/?l=linux-kernel&m=123839202916583 > > > > I also had a separate patchset that, instead of this approach, would just > > iterate through the partial list in get_partial_node() looking for > > anything where the number of free objects met a certain threshold, which > > still defaulted to 25% and instantly picked it. The overhead was taking > > slab_lock() for each page, but that was nullified by the performance > > speedup of using the alloc fastpath a majority of the time for both > > kmalloc-256 and kmalloc-2k when in the past it had only been able to serve > > one or two allocs. If no partial slab met the threshold, the slab_lock() > > is held of the partial slab with the most free objects and returned > > instead. > With the per-cpu partial list, I didn't see any workload which is still > suffering from the list lock, The merge error that you fixed in 3.2-rc1 for hackbench regression is due to add slub to node partial head. And data of hackbench show node partial is still heavy used in allocation. /sys/kernel/slab/kmalloc-256/alloc_fastpath:225208640 /sys/kernel/slab/kmalloc-256/alloc_from_partial:5276300 /sys/kernel/slab/kmalloc-256/alloc_from_pcp:8326041