From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 16A01C433E0 for ; Fri, 12 Jun 2020 16:15:47 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id B741D20801 for ; Fri, 12 Jun 2020 16:15:46 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B741D20801 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 346658D00C8; Fri, 12 Jun 2020 12:15:46 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2F7C38D00A0; Fri, 12 Jun 2020 12:15:46 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1E3D28D00C8; Fri, 12 Jun 2020 12:15:46 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0152.hostedemail.com [216.40.44.152]) by kanga.kvack.org (Postfix) with ESMTP id 09D158D00A0 for ; Fri, 12 Jun 2020 12:15:46 -0400 (EDT) Received: from smtpin06.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id C1664186664 for ; Fri, 12 Jun 2020 16:15:45 +0000 (UTC) X-FDA: 76921060650.06.love99_5d1260a26ddd Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin06.hostedemail.com (Postfix) with ESMTP id C1ED41021B7B4 for ; Fri, 12 Jun 2020 16:15:43 +0000 (UTC) X-HE-Tag: love99_5d1260a26ddd X-Filterd-Recvd-Size: 6176 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf44.hostedemail.com (Postfix) with ESMTP for ; Fri, 12 Jun 2020 16:15:43 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 39361AF4C; Fri, 12 Jun 2020 16:15:45 +0000 (UTC) Subject: Re: [PATCH] mm, page_alloc: skip ->watermark_boost for atomic order-0 allocations-fix To: Charan Teja Kalla , Andrew Morton , mgorman@techsingularity.net, linux-mm@kvack.org Cc: LKML , vinmenon@codeaurora.org References: <31556793-57b1-1c21-1a9d-22674d9bd938@codeaurora.org> From: Vlastimil Babka Message-ID: <1a745bb9-9aca-cdee-e97e-991118b3d2b5@suse.cz> Date: Fri, 12 Jun 2020 18:15:39 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.1 MIME-Version: 1.0 In-Reply-To: <31556793-57b1-1c21-1a9d-22674d9bd938@codeaurora.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: C1ED41021B7B4 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam04 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 6/11/20 2:09 PM, Charan Teja Kalla wrote: > When boosting is enabled, it is observed that rate of atomic order-0 > allocation failures are high due to the fact that free levels in the > system are checked with ->watermark_boost offset. This is not a problem > for sleepable allocations but for atomic allocations which looks like > regression. > > This problem is seen frequently on system setup of Android kernel > running on Snapdragon hardware with 4GB RAM size. When no extfrag event > occurred in the system, ->watermark_boost factor is zero, thus the > watermark configurations in the system are: > _watermark = ( > [WMARK_MIN] = 1272, --> ~5MB > [WMARK_LOW] = 9067, --> ~36MB > [WMARK_HIGH] = 9385), --> ~38MB > watermark_boost = 0 > > After launching some memory hungry applications in Android which can > cause extfrag events in the system to an extent that ->watermark_boost > can be set to max i.e. default boost factor makes it to 150% of high > watermark. > _watermark = ( > [WMARK_MIN] = 1272, --> ~5MB > [WMARK_LOW] = 9067, --> ~36MB > [WMARK_HIGH] = 9385), --> ~38MB > watermark_boost = 14077, -->~57MB > > With default system configuration, for an atomic order-0 allocation to > succeed, having free memory of ~2MB will suffice. But boosting makes > the min_wmark to ~61MB thus for an atomic order-0 allocation to be > successful system should have minimum of ~23MB of free memory(from > calculations of zone_watermark_ok(), min = 3/4(min/2)). But failures are > observed despite system is having ~20MB of free memory. In the testing, > this is reproducible as early as first 300secs since boot and with > furtherlowram configurations(<2GB) it is observed as early as first > 150secs since boot. > > These failures can be avoided by excluding the ->watermark_boost in > watermark caluculations for atomic order-0 allocations. > > Fix-suggested-by: Mel Gorman > Signed-off-by: Charan Teja Reddy For the patch+fix: Acked-by: Vlastimil Babka The boost and highatomic stuff certainly made the whole thing more subtle. > --- > > Change in linux-next: https://lore.kernel.org/patchwork/patch/1244272/ > > mm/page_alloc.c | 36 ++++++++++++++++++++---------------- > 1 file changed, 20 insertions(+), 16 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 0c435b2..18f407e 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -3580,7 +3580,7 @@ bool zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark, > > static inline bool zone_watermark_fast(struct zone *z, unsigned int order, > unsigned long mark, int highest_zoneidx, > - unsigned int alloc_flags) > + unsigned int alloc_flags, gfp_t gfp_mask) > { > long free_pages = zone_page_state(z, NR_FREE_PAGES); > long cma_pages = 0; > @@ -3602,8 +3602,23 @@ static inline bool zone_watermark_fast(struct zone *z, unsigned int order, > mark + z->lowmem_reserve[highest_zoneidx]) > return true; > > - return __zone_watermark_ok(z, order, mark, highest_zoneidx, alloc_flags, > - free_pages); > + if (__zone_watermark_ok(z, order, mark, highest_zoneidx, alloc_flags, > + free_pages)) > + return true; > + /* > + * Ignore watermark boosting for GFP_ATOMIC order-0 allocations > + * when checking the min watermark. The min watermark is the > + * point where boosting is ignored so that kswapd is woken up > + * when below the low watermark. > + */ > + if (unlikely(!order && (gfp_mask & __GFP_ATOMIC) && z->watermark_boost > + && ((alloc_flags & ALLOC_WMARK_MASK) == WMARK_MIN))) { > + mark = z->_watermark[WMARK_MIN]; > + return __zone_watermark_ok(z, order, mark, highest_zoneidx, > + alloc_flags, free_pages); > + } > + > + return false; > } > > bool zone_watermark_ok_safe(struct zone *z, unsigned int order, > @@ -3746,20 +3761,9 @@ static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone) > } > > mark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK); > - /* > - * Allow GFP_ATOMIC order-0 allocations to exclude the > - * zone->watermark_boost in their watermark calculations. > - * We rely on the ALLOC_ flags set for GFP_ATOMIC requests in > - * gfp_to_alloc_flags() for this. Reason not to use the > - * GFP_ATOMIC directly is that we want to fall back to slow path > - * thus wake up kswapd. > - */ > - if (unlikely(!order && !(alloc_flags & ALLOC_WMARK_MASK) && > - (alloc_flags & (ALLOC_HARDER | ALLOC_HIGH)))) { > - mark = zone->_watermark[WMARK_MIN]; > - } > if (!zone_watermark_fast(zone, order, mark, > - ac->highest_zoneidx, alloc_flags)) { > + ac->highest_zoneidx, alloc_flags, > + gfp_mask)) { > int ret; > > #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT >