Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751631Ab0GMEse (ORCPT ); Tue, 13 Jul 2010 00:48:34 -0400 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:37495 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750881Ab0GMEsc (ORCPT ); Tue, 13 Jul 2010 00:48:32 -0400 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 From: KOSAKI Motohiro To: Minchan Kim Subject: Re: [PATCH] vmscan: stop meaningless loop iteration when no reclaimable slab Cc: kosaki.motohiro@jp.fujitsu.com, Andrew Morton , Christoph Lameter , LKML , linux-mm , Mel Gorman , Rik van Riel , Johannes Weiner In-Reply-To: References: <20100709195625.FA28.A69D9226@jp.fujitsu.com> Message-Id: <20100712101237.EA0E.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Mailer: Becky! ver. 2.50.07 [ja] Date: Tue, 13 Jul 2010 13:48:24 +0900 (JST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1688 Lines: 69 Hi > > old shrink_slab > > shrinker->nr += delta; /* Add delta to previous shrinker's remained count */ > total_scan = shrinker->nr; > > while(total_scan >= SHRINK_BATCH) { > nr_before = shrink(xxx); > total_scan =- this_scan; > } > > shrinker->nr += total_scan; > > The total_scan can always be the number < SHRINK_BATCH. > So, when next shrinker calcuates loop count, the number can affect. Correct. > > new shrink_slab > > shrinker->nr += delta; /* nr is always zero by your patch */ no. my patch don't change delta calculation at all. > total_scan = shrinker->nr; > > while(total_scan >= SHRINK_BATCH) { > nr_before = shrink(xxx); > if (nr_before == 0) { > total_scan = 0; > break; > } > } > > shrinker->nr += 0; > > But after your patch, total_scan is always zero. It never affect > next shrinker's loop count. No. after my patch this loop has two exiting way 1) total_scan are less than SHRINK_BATCH. -> no behavior change. we still pass shrinker->nr += total_scan code. 2) (*shrinker->shrink)(0, gfp_mask) return 0 don't increase shrinker->nr. because two reason, a) if total_scan are 10000, we shouldn't carry over such big number. b) now, we have zero slab objects, then we have been freed form the guilty of keeping balance page and slab reclaim. shrinker->nr += 0; have zero side effect. Thanks. > > Am I missing something? > -- > Kind regards, > Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/