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bh=1CqYEUJwt6aLzQ4KOZXFVSUAM01BociElAUc+Y4eAbY=; b=FbxcXiJw8xkFgGCLOChcBWLVobGdIZIh1K+hR2SNpiMSYo9HggQG/vDsyz4xxEoLPKHDFK IkYrbpfkDCKDuA2UEF49mCGBX13QuPIwb27R5NHwmSlI+DZgdsaxatEqyvOyGv0zM8AAmU rIHQThZiA0UeS6uw78ZJpnW7miAHne4= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 3683E13524; Thu, 9 Nov 2023 10:33:25 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id wi81DXW1TGXEdgAAMHmgww (envelope-from ); Thu, 09 Nov 2023 10:33:25 +0000 Date: Thu, 9 Nov 2023 11:33:24 +0100 From: Michal Hocko To: Charan Teja Kalla Cc: akpm@linux-foundation.org, mgorman@techsingularity.net, david@redhat.com, vbabka@suse.cz, hannes@cmpxchg.org, quic_pkondeti@quicinc.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH V3 3/3] mm: page_alloc: drain pcp lists before oom kill Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Stat-Signature: 6xt8yarinc43qpguab5wkf4cppwdt93t X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: AC35F40010 X-HE-Tag: 1699526006-970796 X-HE-Meta: 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 DfMyr8eO 9X0N/dIf5yZ2DH4a220ZbMhVv3BbfsxWR2RK3NxMPofZEBRA7MtRdcUTLIVrf+tWJtLXqDOmzFA9VwObZ48/uz8ySxpeYAVKrHKM5tKGr2SC+KcHJc935heTZTTxxcPA1pRz2BAPgPhBL8gZeb2XmrjfzRcZGHyy3nXjLElm4Bkcv33zDlaIVLxCl7cOBMTQzC6vaJoVFLpyIkCT1qkvN6dnHa5CJNdCe8orpyFVvBLpXHp2k1n2DjPLhAZcposeYpFE3sSxP1JafxAxUd/aDT6rnT9885sOI7gQt 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: List-Subscribe: List-Unsubscribe: On Sun 05-11-23 18:20:50, Charan Teja Kalla wrote: > pcp lists are drained from __alloc_pages_direct_reclaim(), only if some > progress is made in the attempt. > > struct page *__alloc_pages_direct_reclaim() { > ..... > *did_some_progress = __perform_reclaim(gfp_mask, order, ac); > if (unlikely(!(*did_some_progress))) > goto out; > retry: > page = get_page_from_freelist(); > if (!page && !drained) { > drain_all_pages(NULL); > drained = true; > goto retry; > } > out: > } > > After the above, allocation attempt can fallback to > should_reclaim_retry() to decide reclaim retries. If it too return > false, allocation request will simply fallback to oom kill path without > even attempting the draining of the pcp pages that might help the > allocation attempt to succeed. > > VM system running with ~50MB of memory shown the below stats during OOM > kill: > Normal free:760kB boost:0kB min:768kB low:960kB high:1152kB > reserved_highatomic:0KB managed:49152kB free_pcp:460kB > > Though in such system state OOM kill is imminent, but the current kill > could have been delayed if the pcp is drained as pcp + free is even > above the high watermark. TBH I am not sure this is really worth it. Does it really reduce the risk of the OOM in any practical situation? > Fix this missing drain of pcp list in should_reclaim_retry() along with > unreserving the high atomic page blocks, like it is done in > __alloc_pages_direct_reclaim(). > > Signed-off-by: Charan Teja Kalla > --- > mm/page_alloc.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index b91c99e..8eee292 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -3857,8 +3857,10 @@ should_reclaim_retry(gfp_t gfp_mask, unsigned order, > cond_resched(); > out: > /* Before OOM, exhaust highatomic_reserve */ > - if (!ret) > - return unreserve_highatomic_pageblock(ac, true); > + if (!ret) { > + ret = unreserve_highatomic_pageblock(ac, true); > + drain_all_pages(NULL); > + } > > return ret; > } > -- > 2.7.4 -- Michal Hocko SUSE Labs