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Mon, 28 Oct 2024 18:29:45 +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 HhgkNhnYH2eNRwAAD6G6ig (envelope-from ); Mon, 28 Oct 2024 18:29:45 +0000 Message-ID: <0c8205b3-29e2-4edb-be5d-5abf0183696b@suse.cz> Date: Mon, 28 Oct 2024 19:29:45 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH mm-unstable v2] mm/page_alloc: keep track of free highatomic 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> <8459b884-5877-41bd-a882-546e046b9dad@suse.cz> <6ac7a38f-30df-4403-8723-a43829bcdba5@suse.cz> 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+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-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: AC2BA4000B X-Stat-Signature: wdofdhaz4ksesmp9wmax545zfgdkacy8 X-HE-Tag: 1730140157-531912 X-HE-Meta: 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 ziZ2NBSR 290c0qCYwgxWvYbtkuz6tRw3Qay1ztTItL+LjFcqGp9P9Oox/Cut3/4Fc1vnwztT7u93ptL3OdQeIBEmNBLt8QGR7dVEQTciep0EswLThJglwPVS+dYtapaatuBw8d8VNOhD85UEkeFmyxqeBGl9dnVWH1pDJSgFsQzUJ/l0azGIri1YzKlFdtIRf5RqX4qlP5cW3B/v3LPFMxQsRfdjAUwvcJWf3/8ee6/CEfbPpYKOUScK0iNs5C/GCGwcVXhqqehp+sNuaQ2wNEPD+Y3SKcO77e1M9oZI+5PzweKDdSQV7LYyCR1LpCiz0xYQ77LixFSLAebGGQ/5yQctJtjpzJP00UQdIMIsgRDoYkxtcchguk2E= 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 10/28/24 18:54, Yu Zhao wrote: > On Mon, Oct 28, 2024 at 5:01 AM Vlastimil Babka wrote: >> >> Yes you're right. But since we don't plan to backport it beyond 6.12, >> sorry for sidetracking the discussion unnecessarily. More importantly, >> is it possible to change the implementation as I suggested? > > The only reason I didn't fold account_highatomic_freepages() into > account_freepages() is because the former must be called under the > zone lock, which is also how the latter is called but not as a > requirement. Ah, I guess we can document the requirement/add an lockdep assert. Using __mod_zone_page_state() already implies some context restrictions although not zone lock specifically. > I understand where you come from when suggesting a new per-cpu counter > for free highatomic. I have to disagree with that because 1) free > highatomic is relatively small and drifting might defeat its purpose; > 2) per-cpu memory is among the top kernel memory overhead in our fleet > -- it really adds up. So I prefer not to use per-cpu counters unless > necessary. OK, didn't think of these drawbacks. > So if it's ok with you, I'll just fold account_highatomic_freepages() > into account_freepages(), but keep the counter as per zone, not per > cpu. OK, thanks! >> [1] Hooking >> to __del_page_from_free_list() and __add_to_free_list() means extra work >> in every loop iteration in expand() and __free_one_page(). The >> migratetype hygiene should ensure it's not necessary to intercept every >> freelist add/move and hooking to account_freepages() should be >> sufficient and in line with the intended design. > > Agreed.