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Sun, 21 Dec 2025 20:43:02 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id ZvoiMNZbSGnnXAAAD6G6ig (envelope-from ); Sun, 21 Dec 2025 20:43:02 +0000 Message-ID: <9fcd1188-8ad7-4c7b-afd8-647d97b7aae1@suse.cz> Date: Sun, 21 Dec 2025 21:43:02 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm, page_alloc, thp: prevent reclaim for __GFP_THISNODE THP allocations To: Andrew Morton Cc: Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , David Rientjes , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Mike Rapoport , Joshua Hahn , Pedro Falcato , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20251219-costly-noretry-thisnode-fix-v1-1-e1085a4a0c34@suse.cz> <20251220141601.e6694f904167bf12fa319a89@linux-foundation.org> Content-Language: en-US From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJnyBr8BQka0IFQAAoJECJPp+fMgqZkqmMQ AIbGN95ptUMUvo6aAdhxaOCHXp1DfIBuIOK/zpx8ylY4pOwu3GRe4dQ8u4XS9gaZ96Gj4bC+ jwWcSmn+TjtKW3rH1dRKopvC07tSJIGGVyw7ieV/5cbFffA8NL0ILowzVg8w1ipnz1VTkWDr 2zcfslxJsJ6vhXw5/npcY0ldeC1E8f6UUoa4eyoskd70vO0wOAoGd02ZkJoox3F5ODM0kjHu Y97VLOa3GG66lh+ZEelVZEujHfKceCw9G3PMvEzyLFbXvSOigZQMdKzQ8D/OChwqig8wFBmV QCPS4yDdmZP3oeDHRjJ9jvMUKoYODiNKsl2F+xXwyRM2qoKRqFlhCn4usVd1+wmv9iLV8nPs 2Db1ZIa49fJet3Sk3PN4bV1rAPuWvtbuTBN39Q/6MgkLTYHb84HyFKw14Rqe5YorrBLbF3rl M51Dpf6Egu1yTJDHCTEwePWug4XI11FT8lK0LNnHNpbhTCYRjX73iWOnFraJNcURld1jL1nV r/LRD+/e2gNtSTPK0Qkon6HcOBZnxRoqtazTU6YQRmGlT0v+rukj/cn5sToYibWLn+RoV1CE Qj6tApOiHBkpEsCzHGu+iDQ1WT0Idtdynst738f/uCeCMkdRu4WMZjteQaqvARFwCy3P/jpK uvzMtves5HvZw33ZwOtMCgbpce00DaET4y/UzsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZ8gcVAUJFhTonwAKCRAiT6fnzIKmZLY8D/9uo3Ut9yi2YCuASWxr7QQZ lJCViArjymbxYB5NdOeC50/0gnhK4pgdHlE2MdwF6o34x7TPFGpjNFvycZqccSQPJ/gibwNA zx3q9vJT4Vw+YbiyS53iSBLXMweeVV1Jd9IjAoL+EqB0cbxoFXvnjkvP1foiiF5r73jCd4PR rD+GoX5BZ7AZmFYmuJYBm28STM2NA6LhT0X+2su16f/HtummENKcMwom0hNu3MBNPUOrujtW khQrWcJNAAsy4yMoJ2Lw51T/5X5Hc7jQ9da9fyqu+phqlVtn70qpPvgWy4HRhr25fCAEXZDp xG4RNmTm+pqorHOqhBkI7wA7P/nyPo7ZEc3L+ZkQ37u0nlOyrjbNUniPGxPxv1imVq8IyycG AN5FaFxtiELK22gvudghLJaDiRBhn8/AhXc642/Z/yIpizE2xG4KU4AXzb6C+o7LX/WmmsWP Ly6jamSg6tvrdo4/e87lUedEqCtrp2o1xpn5zongf6cQkaLZKQcBQnPmgHO5OG8+50u88D9I rywqgzTUhHFKKF6/9L/lYtrNcHU8Z6Y4Ju/MLUiNYkmtrGIMnkjKCiRqlRrZE/v5YFHbayRD dJKXobXTtCBYpLJM4ZYRpGZXne/FAtWNe4KbNJJqxMvrTOrnIatPj8NhBVI0RSJRsbilh6TE m6M14QORSWTLRg== In-Reply-To: <20251220141601.e6694f904167bf12fa319a89@linux-foundation.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: DE0C140005 X-Stat-Signature: ws5sdc5z314h4e865eepa3sn5o1jsx7n X-HE-Tag: 1766349784-361321 X-HE-Meta: U2FsdGVkX1/P0IEqrpXO+SNJsHpoz9nTYyBygEwHgViSzZioXzlwaaNaioJSBgDkVQdl5VmRxsmsWNT/AYwxjmAip/hjf/L7vsU2Ig9ipQ7zpJekgg5itXvsWD9w80GG628p/EnEd5CG42H2WRA9vIaJFoSPOHSlUZXT56Tf5Uqbbx4gbz+RroffgzjBhg0v48oSWUmghbA3v5JV21Qai7eO1vkqg09SbsHW5/1CWxp0XcbTWfZ1uxek+azpbMBznBIh/207ncGU2u9N4dr8va1kpdEhuFQxUJoPJgTqNZlkfPxxcNz4/XGYr1zvyVwbGpC1Cqv2zLlAvTEPoTqv9Y2ahh1hNCyHOsHcbAr3wrf7c+NQiPLNTIbi4zyAfAqfs7zRr/McrXbLdQ4KqS8e4nWo5zXQVOlFACK11hRFYGVkCJ9QQBeuAWV9OaArpaDw/TuBgE2PIjrEzgMfPhuGK4bg5pBA7WQrTU2Ln+4dX6ETdWRMsULrTKMxTD0TDxL/kk0S/2r2yow2SwK3T10UJtdSrTdiUVbh3/hnOwkuq6aSsU+iCFMPKQh6jj4Nv6+Yw/fjdIatXw/Si1ZaBJSqE9ONapzV+z3A1dBi2hnkcjZrR+NJKNmZFVLCmItUOhTZon9k83e4r4BDvH5wc2KQ6WbEtoZV6xqKm04NSYoAjMOIRFONHKL7rzI49U5TodIDgafgXNoissR15M7fFI+VkNT/srE7ABaul1ZQ3/piHylKls3hFCy/+irnTPq/kZOZMN9dndUn/TU1qevIaamzAbqL2K4VXMkkSkUepB1gEAbpnOGtsRpz6rKUN65Ga8S0BW8JXWCFSGEdYFgjY9Ivm2H1gOFyNznoS0V8GsDaT1leFo3no0n7c+/yngMdJ+fI4ZLfbpZULidEMlolsNnXO1v0WNL03crVsO51dAplalgNJWEmnMtHifAjpOpIdIIcjrfM9DWQXVPH992NJwH jo6xYjkt myqDLHN7aflYMDDYSwMAzvJOltiH6f9tQe5p+ntvmnSTfyinoEc5xwuyYZ6WFAEDBrhHQg3TgvQi2JtmPKx9Fk5Qv4w1B+4DXW0VkR2nowvcGkJeeXHUnZTyZEpAImy8WsQiJSA7CBc6O7xMRayOuUegkfFxSAqCpwJRHGwEJ0RlHWpBDFNmMR2E2Iddcy/5MbMvVULJbsH7rFrmdimPjt3ECiJU9ZtgDI3MWmFDDkYF6UkTcTZOwlOYUzZH0m4JDt0fhmiFpeSJ77Vvha5Y6bRd2Ms0buSdHa8BGWYn5niQtzqyhTs3yULhVPj7nsS4uqcdLBWvr4NAlV3pX7xjPGaTBHsSofVAG+EC8oy6gllkpFFUZKm0ARADOKQersCcBq1yD8eJ7dKpjtlyIj8MeYcvn2Q== 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 12/20/25 23:16, Andrew Morton wrote: > On Fri, 19 Dec 2025 17:31:57 +0100 Vlastimil Babka wrote: > >> Since commit cc638f329ef6 ("mm, thp: tweak reclaim/compaction effort of >> local-only and all-node allocations"), THP page fault allocations have >> settled on the following scheme (from the commit log): >> >> 1. local node only THP allocation with no reclaim, just compaction. >> 2. for madvised VMA's or when synchronous compaction is enabled always - THP >> allocation from any node with effort determined by global defrag setting >> and VMA madvise >> 3. fallback to base pages on any node >> >> Recent customer reports however revealed we have a gap in step 1 above. >> What we have seen is excessive reclaim due to THP page faults on a NUMA >> node that's close to its high watermark, while other nodes have plenty >> of free memory. >> >> The problem with step 1 is that it promises no reclaim after the >> compaction attempt, however reclaim is only avoided for certain >> compaction outcomes (deferred, or skipped due to insufficient free base >> pages), and not e.g. when compaction is actually performed but fails (we >> did see compact_fail vmstat counter increasing). >> >> THP page faults can therefore exhibit a zone_reclaim_mode-like behavior, >> which is not the intention. >> >> Thus add a check for __GFP_THISNODE that corresponds to this exact >> situation and prevents continuing with reclaim/compaction once the >> initial compaction attempt isn't successful in allocating the page. >> >> Note that commit cc638f329ef6 has not introduced this over-reclaim >> possibility; it appears to exist in some form since commit 2f0799a0ffc0 >> ("mm, thp: restore node-local hugepage allocations"). Followup commits >> b39d0ee2632d ("mm, page_alloc: avoid expensive reclaim when compaction >> may not succeed") and cc638f329ef6 have moved in the right direction, >> but left the abovementioned gap. > > Cool. What are your thoughts on which kernel version(s) should receive > this? We could just cc stable and let Fixes: do the job. Should be safe to backport.