From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx123.postini.com [74.125.245.123]) by kanga.kvack.org (Postfix) with SMTP id 76ECF6B0002 for ; Wed, 20 Mar 2013 21:20:26 -0400 (EDT) Message-ID: <514A604E.40303@redhat.com> Date: Wed, 20 Mar 2013 21:20:14 -0400 From: Rik van Riel MIME-Version: 1.0 Subject: Re: [PATCH 05/10] mm: vmscan: Do not allow kswapd to scan at maximum priority References: <1363525456-10448-1-git-send-email-mgorman@suse.de> <1363525456-10448-6-git-send-email-mgorman@suse.de> In-Reply-To: <1363525456-10448-6-git-send-email-mgorman@suse.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman Cc: Linux-MM , Jiri Slaby , Valdis Kletnieks , Zlatko Calusic , Johannes Weiner , dormando , Satoru Moriya , Michal Hocko , LKML On 03/17/2013 09:04 AM, Mel Gorman wrote: > Page reclaim at priority 0 will scan the entire LRU as priority 0 is > considered to be a near OOM condition. Kswapd can reach priority 0 quite > easily if it is encountering a large number of pages it cannot reclaim > such as pages under writeback. When this happens, kswapd reclaims very > aggressively even though there may be no real risk of allocation failure > or OOM. > > This patch prevents kswapd reaching priority 0 and trying to reclaim > the world. Direct reclaimers will still reach priority 0 in the event > of an OOM situation. > > Signed-off-by: Mel Gorman > --- > mm/vmscan.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 7513bd1..af3bb6f 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -2891,7 +2891,7 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order, > */ > if (raise_priority || !this_reclaimed) > sc.priority--; > - } while (sc.priority >= 0 && > + } while (sc.priority >= 1 && > !pgdat_balanced(pgdat, order, *classzone_idx)); > > out: > If priority 0 is way way way way way too aggressive, what makes priority 1 safe? This makes me wonder, are the priorities useful at all to kswapd? -- 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