Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754182AbaFXPmz (ORCPT ); Tue, 24 Jun 2014 11:42:55 -0400 Received: from cantor2.suse.de ([195.135.220.15]:47554 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751859AbaFXPmy (ORCPT ); Tue, 24 Jun 2014 11:42:54 -0400 Message-ID: <53A99C7A.7000806@suse.cz> Date: Tue, 24 Jun 2014 17:42:50 +0200 From: Vlastimil Babka User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0 MIME-Version: 1.0 To: Joonsoo Kim 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() References: <1403279383-5862-1-git-send-email-vbabka@suse.cz> <1403279383-5862-5-git-send-email-vbabka@suse.cz> <20140624083325.GG4836@js1304-P5Q-DELUXE> In-Reply-To: <20140624083325.GG4836@js1304-P5Q-DELUXE> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. > 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/