Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752569AbaF0FwS (ORCPT ); Fri, 27 Jun 2014 01:52:18 -0400 Received: from lgeamrelo04.lge.com ([156.147.1.127]:56233 "EHLO lgeamrelo04.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751127AbaF0FwQ (ORCPT ); Fri, 27 Jun 2014 01:52:16 -0400 X-Original-SENDERIP: 10.177.220.145 X-Original-MAILFROM: iamjoonsoo.kim@lge.com Date: Fri, 27 Jun 2014 14:57:08 +0900 From: Joonsoo Kim To: Vlastimil Babka Cc: linux-mm@kvack.org, Andrew Morton , David Rientjes , Minchan Kim , Mel Gorman , Michal Nazarewicz , Naoya Horiguchi , Christoph Lameter , Rik van Riel , Zhang Yanfei , linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 04/13] mm, compaction: move pageblock checks up from isolate_migratepages_range() Message-ID: <20140627055708.GA9511@js1304-P5Q-DELUXE> References: <1403279383-5862-1-git-send-email-vbabka@suse.cz> <1403279383-5862-5-git-send-email-vbabka@suse.cz> <20140624083325.GG4836@js1304-P5Q-DELUXE> <53A99C7A.7000806@suse.cz> <20140625005335.GA29373@js1304-P5Q-DELUXE> <53AA8F67.5020700@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <53AA8F67.5020700@suse.cz> 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 Wed, Jun 25, 2014 at 10:59:19AM +0200, Vlastimil Babka wrote: > On 06/25/2014 02:53 AM, Joonsoo Kim wrote: > >On Tue, Jun 24, 2014 at 05:42:50PM +0200, Vlastimil Babka wrote: > >>On 06/24/2014 10:33 AM, Joonsoo Kim wrote: > >>>On Fri, Jun 20, 2014 at 05:49:34PM +0200, Vlastimil Babka wrote: > >>>>isolate_migratepages_range() is the main function of the compaction scanner, > >>>>called either on a single pageblock by isolate_migratepages() during regular > >>>>compaction, or on an arbitrary range by CMA's __alloc_contig_migrate_range(). > >>>>It currently perfoms two pageblock-wide compaction suitability checks, and > >>>>because of the CMA callpath, it tracks if it crossed a pageblock boundary in > >>>>order to repeat those checks. > >>>> > >>>>However, closer inspection shows that those checks are always true for CMA: > >>>>- isolation_suitable() is true because CMA sets cc->ignore_skip_hint to true > >>>>- migrate_async_suitable() check is skipped because CMA uses sync compaction > >>>> > >>>>We can therefore move the checks to isolate_migratepages(), reducing variables > >>>>and simplifying isolate_migratepages_range(). The update_pageblock_skip() > >>>>function also no longer needs set_unsuitable parameter. > >>>> > >>>>Furthermore, going back to compact_zone() and compact_finished() when pageblock > >>>>is unsuitable is wasteful - the checks are meant to skip pageblocks quickly. > >>>>The patch therefore also introduces a simple loop into isolate_migratepages() > >>>>so that it does not return immediately on pageblock checks, but keeps going > >>>>until isolate_migratepages_range() gets called once. Similarily to > >>>>isolate_freepages(), the function periodically checks if it needs to reschedule > >>>>or abort async compaction. > >>>> > >>>>Signed-off-by: Vlastimil Babka > >>>>Cc: Minchan Kim > >>>>Cc: Mel Gorman > >>>>Cc: Joonsoo Kim > >>>>Cc: Michal Nazarewicz > >>>>Cc: Naoya Horiguchi > >>>>Cc: Christoph Lameter > >>>>Cc: Rik van Riel > >>>>Cc: David Rientjes > >>>>--- > >>>> mm/compaction.c | 112 +++++++++++++++++++++++++++++--------------------------- > >>>> 1 file changed, 59 insertions(+), 53 deletions(-) > >>>> > >>>>diff --git a/mm/compaction.c b/mm/compaction.c > >>>>index 3064a7f..ebe30c9 100644 > >>>>--- a/mm/compaction.c > >>>>+++ b/mm/compaction.c > >>>>@@ -132,7 +132,7 @@ void reset_isolation_suitable(pg_data_t *pgdat) > >>>> */ > >>>> static void update_pageblock_skip(struct compact_control *cc, > >>>> struct page *page, unsigned long nr_isolated, > >>>>- bool set_unsuitable, bool migrate_scanner) > >>>>+ bool migrate_scanner) > >>>> { > >>>> struct zone *zone = cc->zone; > >>>> unsigned long pfn; > >>>>@@ -146,12 +146,7 @@ static void update_pageblock_skip(struct compact_control *cc, > >>>> if (nr_isolated) > >>>> return; > >>>> > >>>>- /* > >>>>- * Only skip pageblocks when all forms of compaction will be known to > >>>>- * fail in the near future. > >>>>- */ > >>>>- if (set_unsuitable) > >>>>- set_pageblock_skip(page); > >>>>+ set_pageblock_skip(page); > >>>> > >>>> pfn = page_to_pfn(page); > >>>> > >>>>@@ -180,7 +175,7 @@ static inline bool isolation_suitable(struct compact_control *cc, > >>>> > >>>> static void update_pageblock_skip(struct compact_control *cc, > >>>> struct page *page, unsigned long nr_isolated, > >>>>- bool set_unsuitable, bool migrate_scanner) > >>>>+ bool migrate_scanner) > >>>> { > >>>> } > >>>> #endif /* CONFIG_COMPACTION */ > >>>>@@ -345,8 +340,7 @@ isolate_fail: > >>>> > >>>> /* Update the pageblock-skip if the whole pageblock was scanned */ > >>>> if (blockpfn == end_pfn) > >>>>- update_pageblock_skip(cc, valid_page, total_isolated, true, > >>>>- false); > >>>>+ update_pageblock_skip(cc, valid_page, total_isolated, false); > >>>> > >>>> count_compact_events(COMPACTFREE_SCANNED, nr_scanned); > >>>> if (total_isolated) > >>>>@@ -474,14 +468,12 @@ unsigned long > >>>> isolate_migratepages_range(struct zone *zone, struct compact_control *cc, > >>>> unsigned long low_pfn, unsigned long end_pfn, bool unevictable) > >>>> { > >>>>- unsigned long last_pageblock_nr = 0, pageblock_nr; > >>>> unsigned long nr_scanned = 0, nr_isolated = 0; > >>>> struct list_head *migratelist = &cc->migratepages; > >>>> struct lruvec *lruvec; > >>>> unsigned long flags; > >>>> bool locked = false; > >>>> struct page *page = NULL, *valid_page = NULL; > >>>>- bool set_unsuitable = true; > >>>> const isolate_mode_t mode = (cc->mode == MIGRATE_ASYNC ? > >>>> ISOLATE_ASYNC_MIGRATE : 0) | > >>>> (unevictable ? ISOLATE_UNEVICTABLE : 0); > >>>>@@ -545,28 +537,6 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc, > >>>> if (!valid_page) > >>>> valid_page = page; > >>>> > >>>>- /* If isolation recently failed, do not retry */ > >>>>- pageblock_nr = low_pfn >> pageblock_order; > >>>>- if (last_pageblock_nr != pageblock_nr) { > >>>>- int mt; > >>>>- > >>>>- last_pageblock_nr = pageblock_nr; > >>>>- if (!isolation_suitable(cc, page)) > >>>>- goto next_pageblock; > >>>>- > >>>>- /* > >>>>- * For async migration, also only scan in MOVABLE > >>>>- * blocks. Async migration is optimistic to see if > >>>>- * the minimum amount of work satisfies the allocation > >>>>- */ > >>>>- mt = get_pageblock_migratetype(page); > >>>>- if (cc->mode == MIGRATE_ASYNC && > >>>>- !migrate_async_suitable(mt)) { > >>>>- set_unsuitable = false; > >>>>- goto next_pageblock; > >>>>- } > >>>>- } > >>>>- > >>>> /* > >>>> * Skip if free. page_order cannot be used without zone->lock > >>>> * as nothing prevents parallel allocations or buddy merging. > >>>>@@ -668,8 +638,7 @@ next_pageblock: > >>>> * if the whole pageblock was scanned without isolating any page. > >>>> */ > >>>> if (low_pfn == end_pfn) > >>>>- update_pageblock_skip(cc, valid_page, nr_isolated, > >>>>- set_unsuitable, true); > >>>>+ update_pageblock_skip(cc, valid_page, nr_isolated, true); > >>>> > >>>> trace_mm_compaction_isolate_migratepages(nr_scanned, nr_isolated); > >>>> > >>>>@@ -840,34 +809,74 @@ typedef enum { > >>>> } isolate_migrate_t; > >>>> > >>>> /* > >>>>- * Isolate all pages that can be migrated from the block pointed to by > >>>>- * the migrate scanner within compact_control. > >>>>+ * Isolate all pages that can be migrated from the first suitable block, > >>>>+ * starting at the block pointed to by the migrate scanner pfn within > >>>>+ * compact_control. > >>>> */ > >>>> static isolate_migrate_t isolate_migratepages(struct zone *zone, > >>>> struct compact_control *cc) > >>>> { > >>>> unsigned long low_pfn, end_pfn; > >>>>+ struct page *page; > >>>> > >>>>- /* Do not scan outside zone boundaries */ > >>>>- low_pfn = max(cc->migrate_pfn, zone->zone_start_pfn); > >>>>+ /* Start at where we last stopped, or beginning of the zone */ > >>>>+ low_pfn = cc->migrate_pfn; > >>>> > >>>> /* Only scan within a pageblock boundary */ > >>>> end_pfn = ALIGN(low_pfn + 1, pageblock_nr_pages); > >>>> > >>>>- /* Do not cross the free scanner or scan within a memory hole */ > >>>>- if (end_pfn > cc->free_pfn || !pfn_valid(low_pfn)) { > >>>>- cc->migrate_pfn = end_pfn; > >>>>- return ISOLATE_NONE; > >>>>- } > >>>>+ /* > >>>>+ * Iterate over whole pageblocks until we find the first suitable. > >>>>+ * Do not cross the free scanner. > >>>>+ */ > >>>>+ for (; end_pfn <= cc->free_pfn; > >>>>+ low_pfn = end_pfn, end_pfn += pageblock_nr_pages) { > >>>>+ > >>>>+ /* > >>>>+ * This can potentially iterate a massively long zone with > >>>>+ * many pageblocks unsuitable, so periodically check if we > >>>>+ * need to schedule, or even abort async compaction. > >>>>+ */ > >>>>+ if (!(low_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages)) > >>>>+ && compact_should_abort(cc)) > >>>>+ break; > >>>> > >>>>- /* Perform the isolation */ > >>>>- low_pfn = isolate_migratepages_range(zone, cc, low_pfn, end_pfn, false); > >>>>- if (!low_pfn || cc->contended) > >>>>- return ISOLATE_ABORT; > >>>>+ /* Do not scan within a memory hole */ > >>>>+ if (!pfn_valid(low_pfn)) > >>>>+ continue; > >>>>+ > >>>>+ page = pfn_to_page(low_pfn); > >>>>+ /* If isolation recently failed, do not retry */ > >>>>+ if (!isolation_suitable(cc, page)) > >>>>+ continue; > >>>> > >>>>+ /* > >>>>+ * For async compaction, also only scan in MOVABLE blocks. > >>>>+ * Async compaction is optimistic to see if the minimum amount > >>>>+ * of work satisfies the allocation. > >>>>+ */ > >>>>+ if (cc->mode == MIGRATE_ASYNC && > >>>>+ !migrate_async_suitable(get_pageblock_migratetype(page))) > >>>>+ continue; > >>>>+ > >>>>+ /* Perform the isolation */ > >>>>+ low_pfn = isolate_migratepages_range(zone, cc, low_pfn, > >>>>+ end_pfn, false); > >>>>+ if (!low_pfn || cc->contended) > >>>>+ return ISOLATE_ABORT; > >>>>+ > >>>>+ /* > >>>>+ * Either we isolated something and proceed with migration. Or > >>>>+ * we failed and compact_zone should decide if we should > >>>>+ * continue or not. > >>>>+ */ > >>>>+ break; > >>>>+ } > >>>>+ > >>>>+ /* Record where migration scanner will be restarted */ > >>> > >>>If we make isolate_migratepages* interface like as isolate_freepages*, > >>>we can get more clean and micro optimized code. Because > >>>isolate_migratepages_range() can handle arbitrary range and this patch > >>>make isolate_migratepages() also handle arbitrary range, there would > >>>be some redundant codes. :) > >> > >>I'm not sure if it's worth already. Where is the arbitrary range > >>adding overhead? I can only imagine that next_pageblock: label could > >>do a 'break;' instead of setting up next_capture_pfn, but that's > >>about it AFAICS. > > > >In fact, there is just minor overhead, pfn_valid(). > >And isolate_freepages variants seems to do this correctly. :) > > > >Someone could wonder why there are two isolate_migratepages variants > >with arbitrary range compaction ability. IMHO, one > >isolate_migratepage_xxx for pageblock range and two > >isolate_migratepage_yyy/zzz for compaction and CMA is better > >architecture. > > OK, I will try. But we need to resolve the "where to test for > page_zone() == cc->zone?" question. > Hello, I have no idea here. :) I saw the discussion between you and Naoya, and I also wonder when we should check page_zone == cc->zone. Maybe we need help from more experienced developers such as Andrew and others. 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