From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S967520Ab3DRQKd (ORCPT ); Thu, 18 Apr 2013 12:10:33 -0400 Received: from cantor2.suse.de ([195.135.220.15]:59858 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S966792Ab3DRQKc (ORCPT ); Thu, 18 Apr 2013 12:10:32 -0400 Date: Thu, 18 Apr 2013 16:58:54 +0100 From: Mel Gorman To: Johannes Weiner Cc: Andrew Morton , Jiri Slaby , Valdis Kletnieks , Rik van Riel , Zlatko Calusic , dormando , Michal Hocko , Kamezawa Hiroyuki , Linux-MM , LKML Subject: Re: [PATCH 02/10] mm: vmscan: Obey proportional scanning requirements for kswapd Message-ID: <20130418155854.GA2215@suse.de> References: <1365710278-6807-1-git-send-email-mgorman@suse.de> <1365710278-6807-3-git-send-email-mgorman@suse.de> <20130418150105.GD2018@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20130418150105.GD2018@cmpxchg.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 18, 2013 at 08:01:05AM -0700, Johannes Weiner wrote: > On Thu, Apr 11, 2013 at 08:57:50PM +0100, Mel Gorman wrote: > > @@ -1841,17 +1848,58 @@ static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc) > > lruvec, sc); > > } > > } > > + > > + if (nr_reclaimed < nr_to_reclaim || scan_adjusted) > > + continue; > > + > > /* > > - * On large memory systems, scan >> priority can become > > - * really large. This is fine for the starting priority; > > - * we want to put equal scanning pressure on each zone. > > - * However, if the VM has a harder time of freeing pages, > > - * with multiple processes reclaiming pages, the total > > - * freeing target can get unreasonably large. > > + * For global direct reclaim, reclaim only the number of pages > > + * requested. Less care is taken to scan proportionally as it > > + * is more important to minimise direct reclaim stall latency > > + * than it is to properly age the LRU lists. > > */ > > - if (nr_reclaimed >= nr_to_reclaim && > > - sc->priority < DEF_PRIORITY) > > + if (global_reclaim(sc) && !current_is_kswapd()) > > break; > > + > > + /* > > + * For kswapd and memcg, reclaim at least the number of pages > > + * requested. Ensure that the anon and file LRUs shrink > > + * proportionally what was requested by get_scan_count(). We > > + * stop reclaiming one LRU and reduce the amount scanning > > + * proportional to the original scan target. > > + */ > > + nr_file = nr[LRU_INACTIVE_FILE] + nr[LRU_ACTIVE_FILE]; > > + nr_anon = nr[LRU_INACTIVE_ANON] + nr[LRU_ACTIVE_ANON]; > > + > > + if (nr_file > nr_anon) { > > + unsigned long scan_target = targets[LRU_INACTIVE_ANON] + > > + targets[LRU_ACTIVE_ANON] + 1; > > + lru = LRU_BASE; > > + percentage = nr_anon * 100 / scan_target; > > + } else { > > + unsigned long scan_target = targets[LRU_INACTIVE_FILE] + > > + targets[LRU_ACTIVE_FILE] + 1; > > + lru = LRU_FILE; > > + percentage = nr_file * 100 / scan_target; > > + } > > + > > + /* Stop scanning the smaller of the LRU */ > > + nr[lru] = 0; > > + nr[lru + LRU_ACTIVE] = 0; > > + > > + /* > > + * Recalculate the other LRU scan count based on its original > > + * scan target and the percentage scanning already complete > > + */ > > + lru = (lru == LRU_FILE) ? LRU_BASE : LRU_FILE; > > + nr[lru] = targets[lru] * (100 - percentage) / 100; > > + nr[lru] -= min(nr[lru], (targets[lru] - nr[lru])); > > This doesn't seem right. Say percentage is 60, then > > nr[lru] = targets[lru] * (100 - percentage) / 100; > > sets nr[lru] to 40% of targets[lru], and so in > > nr[lru] -= min(nr[lru], (targets[lru] - nr[lru])); > > targets[lru] - nr[lru] is 60% of targets[lru], making it bigger than > nr[lru], which is in turn subtracted from itself, i.e. it leaves the > remaining type at 0 if >= 50% of the other type were scanned, and at > half of the inverted scan percentage if less than 50% were scanned. > > Would this be more sensible? > > already_scanned = targets[lru] - nr[lru]; > nr[lru] = targets[lru] * percentage / 100; /* adjusted original target */ > nr[lru] -= min(nr[lru], already_scanned); /* minus work already done */ Bah, yes, that was the intent as I was writing it. It's not what came out my fingers. Thanks for the bashing with a clue stick. -- Mel Gorman SUSE Labs From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx167.postini.com [74.125.245.167]) by kanga.kvack.org (Postfix) with SMTP id 159EA6B0006 for ; Thu, 18 Apr 2013 12:10:32 -0400 (EDT) Date: Thu, 18 Apr 2013 16:58:54 +0100 From: Mel Gorman Subject: Re: [PATCH 02/10] mm: vmscan: Obey proportional scanning requirements for kswapd Message-ID: <20130418155854.GA2215@suse.de> References: <1365710278-6807-1-git-send-email-mgorman@suse.de> <1365710278-6807-3-git-send-email-mgorman@suse.de> <20130418150105.GD2018@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20130418150105.GD2018@cmpxchg.org> Sender: owner-linux-mm@kvack.org List-ID: To: Johannes Weiner Cc: Andrew Morton , Jiri Slaby , Valdis Kletnieks , Rik van Riel , Zlatko Calusic , dormando , Michal Hocko , Kamezawa Hiroyuki , Linux-MM , LKML On Thu, Apr 18, 2013 at 08:01:05AM -0700, Johannes Weiner wrote: > On Thu, Apr 11, 2013 at 08:57:50PM +0100, Mel Gorman wrote: > > @@ -1841,17 +1848,58 @@ static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc) > > lruvec, sc); > > } > > } > > + > > + if (nr_reclaimed < nr_to_reclaim || scan_adjusted) > > + continue; > > + > > /* > > - * On large memory systems, scan >> priority can become > > - * really large. This is fine for the starting priority; > > - * we want to put equal scanning pressure on each zone. > > - * However, if the VM has a harder time of freeing pages, > > - * with multiple processes reclaiming pages, the total > > - * freeing target can get unreasonably large. > > + * For global direct reclaim, reclaim only the number of pages > > + * requested. Less care is taken to scan proportionally as it > > + * is more important to minimise direct reclaim stall latency > > + * than it is to properly age the LRU lists. > > */ > > - if (nr_reclaimed >= nr_to_reclaim && > > - sc->priority < DEF_PRIORITY) > > + if (global_reclaim(sc) && !current_is_kswapd()) > > break; > > + > > + /* > > + * For kswapd and memcg, reclaim at least the number of pages > > + * requested. Ensure that the anon and file LRUs shrink > > + * proportionally what was requested by get_scan_count(). We > > + * stop reclaiming one LRU and reduce the amount scanning > > + * proportional to the original scan target. > > + */ > > + nr_file = nr[LRU_INACTIVE_FILE] + nr[LRU_ACTIVE_FILE]; > > + nr_anon = nr[LRU_INACTIVE_ANON] + nr[LRU_ACTIVE_ANON]; > > + > > + if (nr_file > nr_anon) { > > + unsigned long scan_target = targets[LRU_INACTIVE_ANON] + > > + targets[LRU_ACTIVE_ANON] + 1; > > + lru = LRU_BASE; > > + percentage = nr_anon * 100 / scan_target; > > + } else { > > + unsigned long scan_target = targets[LRU_INACTIVE_FILE] + > > + targets[LRU_ACTIVE_FILE] + 1; > > + lru = LRU_FILE; > > + percentage = nr_file * 100 / scan_target; > > + } > > + > > + /* Stop scanning the smaller of the LRU */ > > + nr[lru] = 0; > > + nr[lru + LRU_ACTIVE] = 0; > > + > > + /* > > + * Recalculate the other LRU scan count based on its original > > + * scan target and the percentage scanning already complete > > + */ > > + lru = (lru == LRU_FILE) ? LRU_BASE : LRU_FILE; > > + nr[lru] = targets[lru] * (100 - percentage) / 100; > > + nr[lru] -= min(nr[lru], (targets[lru] - nr[lru])); > > This doesn't seem right. Say percentage is 60, then > > nr[lru] = targets[lru] * (100 - percentage) / 100; > > sets nr[lru] to 40% of targets[lru], and so in > > nr[lru] -= min(nr[lru], (targets[lru] - nr[lru])); > > targets[lru] - nr[lru] is 60% of targets[lru], making it bigger than > nr[lru], which is in turn subtracted from itself, i.e. it leaves the > remaining type at 0 if >= 50% of the other type were scanned, and at > half of the inverted scan percentage if less than 50% were scanned. > > Would this be more sensible? > > already_scanned = targets[lru] - nr[lru]; > nr[lru] = targets[lru] * percentage / 100; /* adjusted original target */ > nr[lru] -= min(nr[lru], already_scanned); /* minus work already done */ Bah, yes, that was the intent as I was writing it. It's not what came out my fingers. Thanks for the bashing with a clue stick. -- 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