Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751704AbcDUEfE (ORCPT ); Thu, 21 Apr 2016 00:35:04 -0400 Received: from out4133-34.mail.aliyun.com ([42.120.133.34]:5286 "EHLO out4133-34.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751280AbcDUEfC (ORCPT ); Thu, 21 Apr 2016 00:35:02 -0400 X-Greylist: delayed 3404 seconds by postgrey-1.27 at vger.kernel.org; Thu, 21 Apr 2016 00:35:01 EDT X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R191e4;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e02c03288;MF=hillf.zj@alibaba-inc.com;NM=1;PH=DS;RN=12;SR=0;TI=SMTPD_----4iuulPT_1461209533; Reply-To: "Hillf Danton" From: "Hillf Danton" To: "'Michal Hocko'" , "'Andrew Morton'" Cc: "'Linus Torvalds'" , "'Johannes Weiner'" , "'Mel Gorman'" , "'David Rientjes'" , "'Tetsuo Handa'" , "'Joonsoo Kim'" , "'Vlastimil Babka'" , , "'LKML'" , "'Michal Hocko'" References: <1461181647-8039-1-git-send-email-mhocko@kernel.org> <1461181647-8039-2-git-send-email-mhocko@kernel.org> In-Reply-To: <1461181647-8039-2-git-send-email-mhocko@kernel.org> Subject: Re: [PATCH 01/14] vmscan: consider classzone_idx in compaction_ready Date: Thu, 21 Apr 2016 11:32:13 +0800 Message-ID: <027701d19b7e$65b48910$311d9b30$@alibaba-inc.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Mailer: Microsoft Outlook 14.0 Thread-Index: AQG1HgS+iScJ1ld6BkmHPkLx52RrNAHP2oKVn75AAEA= Content-Language: zh-cn Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3582 Lines: 81 > > From: Michal Hocko > > while playing with the oom detection rework [1] I have noticed > that my heavy order-9 (hugetlb) load close to OOM ended up in an > endless loop where the reclaim hasn't made any progress but > did_some_progress didn't reflect that and compaction_suitable > was backing off because no zone is above low wmark + 1 << order. > > It turned out that this is in fact an old standing bug in compaction_ready > which ignores the requested_highidx and did the watermark check for > 0 classzone_idx. This succeeds for zone DMA most of the time as the zone > is mostly unused because of lowmem protection. This also means that the > OOM killer wouldn't be triggered for higher order requests even when > there is no reclaim progress and we essentially rely on order-0 request > to find this out. Thanks. > This has been broken in one way or another since > fe4b1b244bdb ("mm: vmscan: when reclaiming for compaction, ensure there > are sufficient free pages available") but only since 7335084d446b ("mm: > vmscan: do not OOM if aborting reclaim to start compaction") we are not > invoking the OOM killer based on the wrong calculation. > > Propagate requested_highidx down to compaction_ready and use it for both > the watermak check and compaction_suitable to fix this issue. > > [1] http://lkml.kernel.org/r/1459855533-4600-1-git-send-email-mhocko@kernel.org > > Acked-by: Vlastimil Babka > Signed-off-by: Michal Hocko > --- Acked-by: Hillf Danton > mm/vmscan.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index c839adc13efd..3e6347e2a5fc 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -2482,7 +2482,7 @@ static bool shrink_zone(struct zone *zone, struct scan_control *sc, > * Returns true if compaction should go ahead for a high-order request, or > * the high-order allocation would succeed without compaction. > */ > -static inline bool compaction_ready(struct zone *zone, int order) > +static inline bool compaction_ready(struct zone *zone, int order, int classzone_idx) > { > unsigned long balance_gap, watermark; > bool watermark_ok; > @@ -2496,7 +2496,7 @@ static inline bool compaction_ready(struct zone *zone, int order) > balance_gap = min(low_wmark_pages(zone), DIV_ROUND_UP( > zone->managed_pages, KSWAPD_ZONE_BALANCE_GAP_RATIO)); > watermark = high_wmark_pages(zone) + balance_gap + (2UL << order); > - watermark_ok = zone_watermark_ok_safe(zone, 0, watermark, 0); > + watermark_ok = zone_watermark_ok_safe(zone, 0, watermark, classzone_idx); > > /* > * If compaction is deferred, reclaim up to a point where > @@ -2509,7 +2509,7 @@ static inline bool compaction_ready(struct zone *zone, int order) > * If compaction is not ready to start and allocation is not likely > * to succeed without it, then keep reclaiming. > */ > - if (compaction_suitable(zone, order, 0, 0) == COMPACT_SKIPPED) > + if (compaction_suitable(zone, order, 0, classzone_idx) == COMPACT_SKIPPED) > return false; > > return watermark_ok; > @@ -2589,7 +2589,7 @@ static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc) > if (IS_ENABLED(CONFIG_COMPACTION) && > sc->order > PAGE_ALLOC_COSTLY_ORDER && > zonelist_zone_idx(z) <= requested_highidx && > - compaction_ready(zone, sc->order)) { > + compaction_ready(zone, sc->order, requested_highidx)) { > sc->compaction_ready = true; > continue; > } > -- > 2.8.0.rc3