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Wed, 23 Oct 2024 09:44:24 +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 RxUVM3jFGGdoMgAAD6G6ig (envelope-from ); Wed, 23 Oct 2024 09:44:24 +0000 Message-ID: Date: Wed, 23 Oct 2024 11:44:24 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH mm-unstable v1] mm/page_alloc: try not to overestimate free highatomic Content-Language: en-US To: Matt Fleming Cc: Yu Zhao , Michal Hocko , Andrew Morton , David Rientjes , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Link Lin , Mel Gorman References: <20241020051315.356103-1-yuzhao@google.com> <82e6d623-bbf3-4dd8-af32-fdfc120fc759@suse.cz> <97ccf48e-f30c-4abd-b8ff-2b5310a8b60f@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-Stat-Signature: cekaenzocxghxe9qthbxumc6kpyssstr X-Rspamd-Queue-Id: 92679140006 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1729676654-696443 X-HE-Meta: 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 FjT8MQ4i DsQ415Bc2TsqH4RPFbiUyu1gZSfW7bb2CtHWv5uaY7DGHIOWjiUJj+63UwZ8/e45xI53VM702eWIdrFTDLd/HXH7x5x1tzS+H3xCvH1jLLz3SIzCMMaUAs3YecVVRVqUJWma4k8L3pHR+NUQKvGMQvK5yb+KabqV5Wkz8a22Pa7q/DpiIlH/M7O13AEkXcZ1ABzbZxJBbCBA6T3Sme+rKcwMaxjXYoxLu97nNjV8gtaYTXjXYbWtW6+WgtFo/cBL1LqD7ouXECTQqpmaEQpROxHF+lWucAgQ0b9rcF6NKHnN3rTwA2UoPJrdB0ZHDHcCjZylm+lT43zyIPuW/vFNj70prDVq8T/YigVkXKYksuyEAFQk= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000079, 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 10/23/24 11:25, Matt Fleming wrote: > On Wed, Oct 23, 2024 at 8:35 AM Vlastimil Babka wrote: >> >> I thought the alloc demand is only blocked on the pessimistic watermark >> calculation. Usable free pages exist, but the allocation is not allowed to >> use them. > > I'm confused -- I thought the problem was the inverse of your > statement: the allocation is attempted because > __zone_watermark_unusable_free() claims the highatomic pages are free > but they're not? AFAICS the fix is about GFP_HIGHUSER_MOVABLE allocation, so not eligible for highatomic reserves. Thus the watermark check in __zone_watermark_unusable_free() will add z->nr_reserved_highatomic as unusable_free, which is then subtracted from actual NR_FREE_PAGES. But since there are little or no actual free highatomic pages within the NR_FREE_PAGES, we're subtracting more than we should and this makes the watermark check very pessimistic and likely to fail. So the allocation is denied even if it would find many non-highatomic pages to allocate, and above the watermark. The problem you describe would apply to a highatomic allocation. Which would then try to reserve more, but maybe conclude we already have too many reserved, and not reserve anything. But highatomic pageblocks that are already full don't really contribute to that reserve anymore, so it would be better to stop marking and counting them as highatomic, and instead allow new ones to be reserved. So I think both kinds of allocations (highatomic or not) are losing here due to full highatomic pageblocks.