From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx114.postini.com [74.125.245.114]) by kanga.kvack.org (Postfix) with SMTP id 7BDB86B02A9 for ; Tue, 13 Dec 2011 21:31:16 -0500 (EST) Subject: Re: [PATCH 1/3] slub: set a criteria for slub node partial adding From: Shaohua Li In-Reply-To: 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: Wed, 14 Dec 2011 10:43:42 +0800 Message-ID: <1323830622.22361.407.camel@sli10-conroe> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: David Rientjes Cc: "Shi, Alex" , Christoph Lameter , "penberg@kernel.org" , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , Andi Kleen On Wed, 2011-12-14 at 09:29 +0800, David Rientjes wrote: > On Mon, 12 Dec 2011, Shaohua Li wrote: > > > With the per-cpu partial list, I didn't see any workload which is still > > suffering from the list lock, so I suppose both the trashing approach > > and pick 25% used slab approach don't help. > > This doesn't necessarily have anything to do with contention on list_lock, > it has to do with the fact that ~99% of allocations come from the slowpath > since the cpu slab only has one free object when it is activated, that's > what the statistics indicated for kmalloc-256 and kmalloc-2k. That's what > I called "slab thrashing": the continual deactivation of the cpu slab and > picking from the partial list that would only have one or two free objects > causing the vast majority of allocations to require the slowpath. if vast majority of allocation needs picking from partial list of node, the list_lock will have contention too. But I'd say avoiding the slab thrashing does increase fastpath. How much it can improve performance I don't know. The slowpath (not involving list_lock case, so picking per-cpu partial list) is already _very_ fast these days. -- 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