Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752874AbaFYAs6 (ORCPT ); Tue, 24 Jun 2014 20:48:58 -0400 Received: from lgeamrelo01.lge.com ([156.147.1.125]:35192 "EHLO lgeamrelo01.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751862AbaFYAs5 (ORCPT ); Tue, 24 Jun 2014 20:48:57 -0400 X-Original-SENDERIP: 10.177.220.145 X-Original-MAILFROM: iamjoonsoo.kim@lge.com Date: Wed, 25 Jun 2014 09:53:35 +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: <20140625005335.GA29373@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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <53A99C7A.7000806@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 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. And, One additional note. You can move update_pageblock_skip() to isolate_migratepages() now. Thanks. -- 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/