From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx171.postini.com [74.125.245.171]) by kanga.kvack.org (Postfix) with SMTP id BA99E6B0033 for ; Fri, 14 Jun 2013 12:16:58 -0400 (EDT) Message-ID: <51BB41EF.7080508@redhat.com> Date: Fri, 14 Jun 2013 12:16:47 -0400 From: Rik van Riel MIME-Version: 1.0 Subject: Re: [PATCH 1/7] mm: remove ZONE_RECLAIM_LOCKED References: <1370445037-24144-1-git-send-email-aarcange@redhat.com> <1370445037-24144-2-git-send-email-aarcange@redhat.com> <20130606090430.GC1936@suse.de> <51B0C8D8.7070708@redhat.com> In-Reply-To: <51B0C8D8.7070708@redhat.com> Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman Cc: Andrea Arcangeli , linux-mm@kvack.org, Hugh Dickins , Richard Davies , Shaohua Li , Rafael Aquini On 06/06/2013 01:37 PM, Rik van Riel wrote: > On 06/06/2013 05:04 AM, Mel Gorman wrote: >> On Wed, Jun 05, 2013 at 05:10:31PM +0200, Andrea Arcangeli wrote: >>> Zone reclaim locked breaks zone_reclaim_mode=1. If more than one >>> thread allocates memory at the same time, it forces a premature >>> allocation into remote NUMA nodes even when there's plenty of clean >>> cache to reclaim in the local nodes. >>> >>> Signed-off-by: Andrea Arcangeli >> >> Be aware that after this patch is applied that it is possible to have a >> situation like this >> >> 1. 4 processes running on node 1 >> 2. Each process tries to allocate 30% of memory >> 3. Each process reads the full buffer in a loop (stupid, just an example) >> >> In this situation the processes will continually interfere with each >> other until one of them gets migrated to another zone by the scheduler. > > This is a very good point. > > Andrea, I suspect we will need some kind of safeguard against > this problem. Never mind me. In __zone_reclaim we set the flags in swap_control so we never unmap pages or swap pages out at all by default, so this should not be an issue at all. In order to get the problem illustrated above, the user will have to enable RECLAIM_SWAP through sysfs manually. The series looks fine as is. -- 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