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[109.81.91.122]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49cee7fec25sm53367115e9.13.2026.09.03.00.27.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 03 Sep 2026 00:27:05 -0700 (PDT) Date: Thu, 3 Sep 2026 09:27:04 +0200 From: Michal Hocko To: Yosry Ahmed Cc: Charan Teja Kalla , 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-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: EFA3C40006 X-Stat-Signature: isbtejw734xxop9f491uopp575qr5ho9 X-HE-Tag: 1788420427-936091 X-HE-Meta: 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 9YAwwTyy Or+BiqqUG37JvpyPrUXl13YOPlpJLcjMPOZUTz9NkV/vN9p+Neb/8OeXkTAiNrfFrAXEx1fbofzYVhFhzV2/OiHsLeRajZXPpMS2Gt+VVqA6KEnHkL7v4LEsYSdtt9hfDya1KBH/zVMChFl/2znLivkJtiQmQpJsKrp9wGra0cNzPQj52XS7777iS24HjI405kzTPkCNpIsttTjPwnTv1dhHDSRjGRNgefD1iZQGA5hKu9CHxYohQpvd1eebsFqc47L8+2zYgj79tvYDgIuenAFKKtHQdZUabXb6UidQ6OJbGFdZoZYrHmFISynzvwreEbGEUtMOCWaDKKDMFNOvC7UPIwElZ585kQRxBCaoCYe8o8eQlc9HtbrF6hjpZ3XfZ9C05JAaWLA3ETTrO0mZ/3XFo5wn++h6eSvrsavQaq1bk4VD1xTvEAjVqOzP5Re3OJyw6/i5HSsEVb50= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed 02-09-26 16:49:48, Yosry Ahmed wrote: > On Sun, Nov 05, 2023 at 06:20:50PM +0530, 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. > > > > 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 > > [Sorry for thread necromancy] > > Hi Charan, > > Are you planning to respin this patch? > > I know that Michal was questioning the need for it. While doing some > stress testing I came across a couple of OOM kills that had significant > amount of memory in pcplists. Something that would have been prevented > by this patch. Could you share some numbers to see the scale of the problem? -- Michal Hocko SUSE Labs