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Tue, 14 Jan 2025 12:51:33 +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 bBtYItVdhmctOgAAD6G6ig (envelope-from ); Tue, 14 Jan 2025 12:51:33 +0000 Message-ID: <1ada3f6d-72bb-46a4-9fef-0bf6a7b32e62@suse.cz> Date: Tue, 14 Jan 2025 13:51:33 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V3] mm: compaction: skip memory compaction when there are not enough migratable pages Content-Language: en-US To: Ge Yang , akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, 21cnbao@gmail.com, david@redhat.com, baolin.wang@linux.alibaba.com, hannes@cmpxchg.org, liuzixing@hygon.cn References: <1736335854-548-1-git-send-email-yangge1116@126.com> <39709cd7-0de6-4247-a70a-9f81fccbce6a@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-Server: rspam03 X-Rspamd-Queue-Id: 98D1D40007 X-Stat-Signature: jo886ztfwr1g4crbot9wzptwcrwi3hra X-HE-Tag: 1736859095-720096 X-HE-Meta: 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 MXWvyTVh 11ByGWwNnXOYw5zJycJ+Vy6yKxONNlwGwsnOL02eaOZZ0EoUwmhfFeBC2yFvxt/2PmzyU86YMsmDI6ZgPYVw0kr10sN6WEOpWsz+EAfdThmFifqOW0nzYXgoirNGJ2llNpX48EXnsWbRogGLmX5DWJzQUWNnoqMWhNOiYTZmYfw+g+ca7ZrwDa6awETlPtKfBpegwN10uSp4bT1y2AeEyJFfBDhVWL3TZdUb2kHu95ExjBvsO3xYs1SKRt52gOkwYaFBP0nRoGGpc4TjxmLe4gjjJu0peuD49Nj7HvJgOeOgby18T+hjGb0V2k1N4lqcT3yWO8ebwxpw+iKvVTXTymHjFXtJ1lwa9oOQIoYzL55nzLKk7KH+rg+GyOOIIhcNQD+Ii1LxbEhiSJ+s= X-Bogosity: Ham, tests=bogofilter, spamicity=0.001611, 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 1/14/25 13:24, Ge Yang wrote: >> Hopefully also when done from the pin_user_pages_remote(..., FOLL_LONGTERM, >> ...) context the allocation gfp_mask correctly lacks __GFP_MOVABLE? > yes. > I guess >> it has to, otherwise it would allocate from the CMA pageblocks. >> >> Then I wonder if we could use the real allocation context to determine >> watermarks, as __compaction_suitable() is passing ALLOC_CMA instead because >> it's checking only for migration targets, which have to be CMA compatible by >> definition. But we could use the real unmovable allocation context to have >> __zone_watermark_unusable_free() subtract CMA pages, and thus we won't pass >> the order-0 check anymore once the non-CMA part is exhausted. >> >> There's some risk that in some different scenario the compaction could in >> fact migrate pages from the exhausted non-CMA part of the zone to the CMA >> part and succeed, and we'll skip it instead. But that should be rare? >> > Below is the previous discussion： > https://lore.kernel.org/lkml/1734436004-1212-1-git-send-email-yangge1116@126.com/ Right so Johannes had the same concern. >> Anyway given that concern I'm not sure about changing >> __compaction_suitable() for every caller like this. We could (at least >> initially) target this heuristic only for COMPACT_PRIO_ASYNC which is being >> used for this THP opportunistic attempt. >> >> So for example: >> - add a new bool flag to compact_control that is true for COMPACT_PRIO_ASYNC >> - pass cc pointer to compaction_suit_allocation_order() >> - in that function, add another check if the the new cc flag is true, >> between the current zone_watermark_ok() and compaction_suitable() checks, >> which works like __compaction_suitable() but uses alloc_flags (which should >> not be ALLOC_CMA in our pinned allocation case) instead of ALLOC_CMA, return >> COMPACT_SKIPPED if it fails. >> > I will send a new version of the patch based on the suggestions here. > Thank you. Yeah that way should hopefully limit the concern sufficiently. Maybe we could also add costly_order condition in addition to COMPACT_PRIO_ASYNC condition to set the new compact_control flag. But only __GFP_NORETRY allocations should be affected in the immediate "goto nopage" when compaction is skipped, others will attempt with DEF_COMPACT_PRIORITY anyway and won't fail without trying to compact-migrate the non-CMA pageblocks into CMA pageblocks first, so it should be fine.