From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with SMTP id 883C66B003D for ; Mon, 14 Dec 2009 09:40:47 -0500 (EST) Message-ID: <4B264E66.9050206@redhat.com> Date: Mon, 14 Dec 2009 09:40:38 -0500 From: Rik van Riel MIME-Version: 1.0 Subject: Re: [PATCH] vmscan: limit concurrent reclaimers in shrink_zone References: <20091210185626.26f9828a@cuia.bos.redhat.com> <87pr6hya86.fsf@basil.nowhere.org> In-Reply-To: <87pr6hya86.fsf@basil.nowhere.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Andi Kleen Cc: lwoodman@redhat.com, kosaki.motohiro@jp.fujitsu.com, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, aarcange@redhat.com List-ID: On 12/14/2009 08:08 AM, Andi Kleen wrote: > Rik van Riel writes: > >> +max_zone_concurrent_reclaim: >> + >> +The number of processes that are allowed to simultaneously reclaim >> +memory from a particular memory zone. >> + >> +With certain workloads, hundreds of processes end up in the page >> +reclaim code simultaneously. This can cause large slowdowns due >> +to lock contention, freeing of way too much memory and occasionally >> +false OOM kills. >> + >> +To avoid these problems, only allow a smaller number of processes >> +to reclaim pages from each memory zone simultaneously. >> + >> +The default value is 8. > > I don't like the hardcoded number. Is the same number good for a 128MB > embedded system as for as 1TB server? Seems doubtful. > > This should be perhaps scaled with memory size and number of CPUs? The limit is per _zone_, so the number of concurrent reclaimers is automatically scaled by the number of memory zones in the system. Scaling up the per-zone value as well looks like it could lead to the kind of lock contention we are aiming to avoid in the first place. -- All rights reversed. -- 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