From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx129.postini.com [74.125.245.129]) by kanga.kvack.org (Postfix) with SMTP id 176B46B0006 for ; Tue, 19 Mar 2013 05:55:20 -0400 (EDT) Date: Tue, 19 Mar 2013 09:55:15 +0000 From: Mel Gorman Subject: Re: [PATCH 01/10] mm: vmscan: Limit the number of pages kswapd reclaims at each priority Message-ID: <20130319095514.GA2055@suse.de> References: <1363525456-10448-1-git-send-email-mgorman@suse.de> <1363525456-10448-2-git-send-email-mgorman@suse.de> <5147A8EC.5010908@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <5147A8EC.5010908@gmail.com> Sender: owner-linux-mm@kvack.org List-ID: To: Simon Jeons Cc: Linux-MM , Jiri Slaby , Valdis Kletnieks , Rik van Riel , Zlatko Calusic , Johannes Weiner , dormando , Satoru Moriya , Michal Hocko , LKML On Tue, Mar 19, 2013 at 07:53:16AM +0800, Simon Jeons wrote: > Hi Mel, > On 03/17/2013 09:04 PM, Mel Gorman wrote: > >The number of pages kswapd can reclaim is bound by the number of pages it > >scans which is related to the size of the zone and the scanning priority. In > >many cases the priority remains low because it's reset every SWAP_CLUSTER_MAX > >reclaimed pages but in the event kswapd scans a large number of pages it > >cannot reclaim, it will raise the priority and potentially discard a large > >percentage of the zone as sc->nr_to_reclaim is ULONG_MAX. The user-visible > >effect is a reclaim "spike" where a large percentage of memory is suddenly > >freed. It would be bad enough if this was just unused memory but because > > Since there is nr_reclaimed >= nr_to_reclaim check if priority is > large than DEF_PRIORITY in shrink_lruvec, how can a large percentage > of memory is suddenly freed happen? > Because of the priority checks made in get_scan_count(). Patch 5 has more detail on why this happens. -- Mel Gorman SUSE Labs -- 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