From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx194.postini.com [74.125.245.194]) by kanga.kvack.org (Postfix) with SMTP id 6789F6B0036 for ; Fri, 14 Jun 2013 10:32:13 -0400 (EDT) Date: Fri, 14 Jun 2013 14:32:11 +0000 From: Christoph Lameter Subject: Re: [PATCH] slub: Avoid direct compaction if possible In-Reply-To: <51BB1802.8050108@yandex-team.ru> Message-ID: <0000013f4319cb46-a5a3de58-1207-4037-ae39-574b58135ea2-000000@email.amazonses.com> References: <51BB1802.8050108@yandex-team.ru> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Roman Gushchin Cc: penberg@kernel.org, mpm@selenic.com, akpm@linux-foundation.org, mgorman@suse.de, rientjes@google.com, glommer@parallels.com, hannes@cmpxchg.org, minchan@kernel.org, jiang.liu@huawei.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org On Fri, 14 Jun 2013, Roman Gushchin wrote: > Slub tries to allocate contiguous pages even if memory is fragmented and > there are no free contiguous pages. In this case it calls direct compaction > to allocate contiguous page. Compaction requires the taking of some heavily > contended locks (e.g. zone locks). So, running compaction (direct and using > kswapd) simultaneously on several processors can cause serious performance > issues. The main thing that this patch does is to add a nocompact flag to the page allocator. That needs to be a separate patch. Also fix the description. Slub does not invoke compaction. The page allocator initiates compaction under certain conditions. > It's possible to avoid such problems (or at least to make them less probable) > by avoiding direct compaction. If it's not possible to allocate a contiguous > page without compaction, slub will fall back to order 0 page(s). In this case > kswapd will be woken to perform asynchronous compaction. So, slub can return > to default order allocations as soon as memory will be de-fragmented. Sounds like a good idea. Do you have some numbers to show the effect of this patch? -- 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/ . Don't email: email@kvack.org