From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx164.postini.com [74.125.245.164]) by kanga.kvack.org (Postfix) with SMTP id E19D56B00B2 for ; Sun, 11 Dec 2011 23:28:12 -0500 (EST) Subject: Re: [PATCH 1/3] slub: set a criteria for slub node partial adding From: "Alex,Shi" In-Reply-To: <1323664514.22361.385.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> <1323663251.16790.6115.camel@debian> <1323664514.22361.385.camel@sli10-conroe> Content-Type: text/plain; charset="UTF-8" Date: Mon, 12 Dec 2011 12:25:21 +0800 Message-ID: <1323663921.16790.6118.camel@debian> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: "Li, Shaohua" Cc: David Rientjes , Christoph Lameter , "penberg@kernel.org" , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , Andi Kleen On Mon, 2011-12-12 at 12:35 +0800, Li, Shaohua wrote: > On Mon, 2011-12-12 at 12:14 +0800, Shi, Alex wrote: > > 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. > The patch is already in base kernel, did you mean even with it you still > saw the list locking issue with latest kernel? > Yes, list_lock still hurt performance. It will be helpful if you can do some optimize for it. -- 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