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Sun, 27 Oct 2024 20:36:39 +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 wu/MOVekHmc3cQAAD6G6ig (envelope-from ); Sun, 27 Oct 2024 20:36:39 +0000 Message-ID: <8459b884-5877-41bd-a882-546e046b9dad@suse.cz> Date: Sun, 27 Oct 2024 21:36:39 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH mm-unstable v2] mm/page_alloc: keep track of free highatomic Content-Language: en-US To: Yu Zhao Cc: Andrew Morton , Johannes Weiner , Zi Yan , Mel Gorman , Matt Fleming , David Rientjes , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Link Lin References: <20241026033625.2237102-1-yuzhao@google.com> <37a28ef7-e477-40b0-a8e4-3d74b747e323@suse.cz> 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+fMgqZkBQJkBREIBQkRadznAAoJECJPp+fMgqZkNxIQ ALZRqwdUGzqL2aeSavbum/VF/+td+nZfuH0xeWiO2w8mG0+nPd5j9ujYeHcUP1edE7uQrjOC Gs9sm8+W1xYnbClMJTsXiAV88D2btFUdU1mCXURAL9wWZ8Jsmz5ZH2V6AUszvNezsS/VIT87 AmTtj31TLDGwdxaZTSYLwAOOOtyqafOEq+gJB30RxTRE3h3G1zpO7OM9K6ysLdAlwAGYWgJJ V4JqGsQ/lyEtxxFpUCjb5Pztp7cQxhlkil0oBYHkudiG8j1U3DG8iC6rnB4yJaLphKx57NuQ PIY0Bccg+r9gIQ4XeSK2PQhdXdy3UWBr913ZQ9AI2usid3s5vabo4iBvpJNFLgUmxFnr73SJ KsRh/2OBsg1XXF/wRQGBO9vRuJUAbnaIVcmGOUogdBVS9Sun/Sy4GNA++KtFZK95U7J417/J Hub2xV6Ehc7UGW6fIvIQmzJ3zaTEfuriU1P8ayfddrAgZb25JnOW7L1zdYL8rXiezOyYZ8Fm ZyXjzWdO0RpxcUEp6GsJr11Bc4F3aae9OZtwtLL/jxc7y6pUugB00PodgnQ6CMcfR/HjXlae h2VS3zl9+tQWHu6s1R58t5BuMS2FNA58wU/IazImc/ZQA+slDBfhRDGYlExjg19UXWe/gMcl De3P1kxYPgZdGE2eZpRLIbt+rYnqQKy8UxlszsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZAUSmwUJDK5EZgAKCRAiT6fnzIKmZOJGEACOKABgo9wJXsbWhGWYO7mD 8R8mUyJHqbvaz+yTLnvRwfe/VwafFfDMx5GYVYzMY9TWpA8psFTKTUIIQmx2scYsRBUwm5VI EurRWKqENcDRjyo+ol59j0FViYysjQQeobXBDDE31t5SBg++veI6tXfpco/UiKEsDswL1WAr tEAZaruo7254TyH+gydURl2wJuzo/aZ7Y7PpqaODbYv727Dvm5eX64HCyyAH0s6sOCyGF5/p eIhrOn24oBf67KtdAN3H9JoFNUVTYJc1VJU3R1JtVdgwEdr+NEciEfYl0O19VpLE/PZxP4wX PWnhf5WjdoNI1Xec+RcJ5p/pSel0jnvBX8L2cmniYnmI883NhtGZsEWj++wyKiS4NranDFlA HdDM3b4lUth1pTtABKQ1YuTvehj7EfoWD3bv9kuGZGPrAeFNiHPdOT7DaXKeHpW9homgtBxj 8aX/UkSvEGJKUEbFL9cVa5tzyialGkSiZJNkWgeHe+jEcfRT6pJZOJidSCdzvJpbdJmm+eED w9XOLH1IIWh7RURU7G1iOfEfmImFeC3cbbS73LQEFGe1urxvIH5K/7vX+FkNcr9ujwWuPE9b 1C2o4i/yZPLXIVy387EjA6GZMqvQUFuSTs/GeBcv0NjIQi8867H3uLjz+mQy63fAitsDwLmR EP+ylKVEKb0Q2A== In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Action: no action X-Rspam-User: X-Rspamd-Queue-Id: C9295100013 X-Rspamd-Server: rspam01 X-Stat-Signature: ob551zgpzsi85k1knht6i5ezes97y8a6 X-HE-Tag: 1730061376-32015 X-HE-Meta: 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 k8ytZV+g 1t64yXebfG4mqKVQARLN1ZmtpraMHwF/yBpS1HOHs9u0d15NjWOxmgeEFc0/0DUOeIDrI55gefMz3uKC3BAVZKwtTcxEDRIGG40hlRZvU9hfKBhbtDxRonOzjPGkSwaQATCLn1LMDe9w9yA+nrqtxUg0qNTHnRF+n19kQM0lEbZjcTolCia4TeQqUb1m0ltH7YThOWPg4n5Cl9L22pFYomN3LFYvL4r/nbI2T3nZavwkanwakQQkIc/jyB98ab6tTAFRtY9rI1yklz94ufCXYJnVbqdHDiD1+n2Clqi5AEMtF8Uyb14oPVII//rfZvQjYNvnw9VQEv1JWi3xyJM/vi2ogFn87Zef7ADp/Uge1OtSk/nQ= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000091, 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 10/27/24 21:17, Yu Zhao wrote: > On Sun, Oct 27, 2024 at 1:53 PM Vlastimil Babka wrote: >> >> On 10/26/24 05:36, Yu Zhao wrote: >> > OOM kills due to vastly overestimated free highatomic reserves were >> > observed: >> > >> > ... invoked oom-killer: gfp_mask=0x100cca(GFP_HIGHUSER_MOVABLE), order=0 ... >> > Node 0 Normal free:1482936kB boost:0kB min:410416kB low:739404kB high:1068392kB reserved_highatomic:1073152KB ... >> > Node 0 Normal: 1292*4kB (ME) 1920*8kB (E) 383*16kB (UE) 220*32kB (ME) 340*64kB (E) 2155*128kB (UE) 3243*256kB (UE) 615*512kB (U) 1*1024kB (M) 0*2048kB 0*4096kB = 1477408kB >> > >> > The second line above shows that the OOM kill was due to the following >> > condition: >> > >> > free (1482936kB) - reserved_highatomic (1073152kB) = 409784KB < min (410416kB) >> > >> > And the third line shows there were no free pages in any >> > MIGRATE_HIGHATOMIC pageblocks, which otherwise would show up as type >> > 'H'. Therefore __zone_watermark_unusable_free() underestimated the >> > usable free memory by over 1GB, which resulted in the unnecessary OOM >> > kill above. >> > >> > The comments in __zone_watermark_unusable_free() warns about the >> > potential risk, i.e., >> > >> > If the caller does not have rights to reserves below the min >> > watermark then subtract the high-atomic reserves. This will >> > over-estimate the size of the atomic reserve but it avoids a search. >> > >> > However, it is possible to keep track of free pages in reserved >> > highatomic pageblocks with a new per-zone counter nr_free_highatomic >> > protected by the zone lock, to avoid a search when calculating the >> >> It's only possible to track this reliably since the "mm: page_alloc: >> freelist migratetype hygiene" patchset was merged, which explains why >> nr_reserved_highatomic was used until now, even if it's imprecise. > > I just refreshed my memory by quickly going through the discussion > around that series and didn't find anything that helps me understand > the above. More pointers please? For example: - a page is on pcplist in MIGRATE_MOVABLE list - we reserve its pageblock as highatomic, which does nothing to the page on the pcplist - page above is flushed from pcplist to zone freelist, but it remembers it was MIGRATE_MOVABLE, merges with another buddy/buddies from the now-highatomic list, the resulting order-X page ends up on the movable freelist despite being in highatomic pageblock. The counter of free highatomic is now wrong wrt the freelist reality The series has addressed various scenarios like that, where page can end up on the wrong freelist.