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Tue, 11 Jun 2024 19:20:28 +0800 (CST) Subject: Re: [PATCH] mm/gup: don't check page lru flag before draining it To: David Hildenbrand , Matthew Wilcox Cc: Baolin Wang , akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, liuzixing@hygon.cn References: <0d7a4405-9a2e-4bd1-ba89-a31486155233@redhat.com> <776de760-e817-43b2-bd00-8ce96f4e37a8@redhat.com> <7063920f-963a-4b3e-a3f3-c5cc227bc877@redhat.com> <48150a28-ed48-49ff-9432-9cd30cda4da4@linux.alibaba.com> <11ef3deb-d1e3-46d5-97ed-9ba3c1fbbba9@redhat.com> <697a9bc2-a655-4035-aa5e-7d3acb23e79d@redhat.com> <3a368e38-a4cb-413e-a6d9-41c6b3dbd5ae@redhat.com> <48fb0e58-16d1-7956-cf35-74741826617a@126.com> <617f9e36-9334-4630-a6b9-473f2dd570d4@redhat.com> From: yangge1116 Message-ID: <8351052a-5c21-c383-544b-3166e883587c@126.com> Date: Tue, 11 Jun 2024 19:20:26 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <617f9e36-9334-4630-a6b9-473f2dd570d4@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-CM-TRANSID:_____wDXvw77Mmhm7thyAw--.44907S2 X-Coremail-Antispam: 1Uf129KBjvJXoW7uF1xWr47XrW7urWrZFyUGFg_yoW8Gw1kpF 18KF98GF4qkryayFn2gwnrArsay3yrXFW5AFy3Zry7CF4DXF1a9rW0qa15CFy3Jr4Sqr1I ya1jq3WkuF15ZaDanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x07b0eOJUUUUU= X-Originating-IP: [118.242.3.34] X-CM-SenderInfo: 51dqwwjhrrila6rslhhfrp/1tbiGA36G2VLbs-xaAAAsi X-Rspam-User: X-Rspamd-Queue-Id: 72F6EA0003 X-Rspamd-Server: rspam01 X-Stat-Signature: ea7ien54rn9baxfjqhu6i8sqgtw9u33y X-HE-Tag: 1718104847-229789 X-HE-Meta: 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 xwx17BjN 4iwWVGhqDGft/O4BphYVCckPOI1I+YlGSW2JNbVY6teLFRh/MYjENRR25dlV28Hk266OF8MtYwNgp2g2PIjpF65NhNEZ6yzz8n0SFKK6Q5YungKZ5p+kE0CqP3Kh1o/Deq07vK8jIPIOeTHeOPxxs5nTtFm9F6ANkXcbQ1UD4/RajndLSi8BblZMPHtQGEezkeQOCgyP+LZEeWMPFW8M5k3/QfAcF7aGwq+LEOiqTA5Rfp9bFkcTC05yrR8yqZ6A69Hxfkh/OMqKj3mcdI2BTlWmgW100xrasqkds0CEdN33rQcMU204RhF/45JT884ooFGLfHgRnn7sYPVgnf51MChUPeFp/lmUmCs6Xt+/m8TXfI2g3vNTKabOUiy0fORaNL6IA3EHhCMVgY1s= 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: 在 2024/6/9 上午12:03, David Hildenbrand 写道: > On 08.06.24 17:15, Matthew Wilcox wrote: >> On Sat, Jun 08, 2024 at 12:38:49PM +0800, yangge1116 wrote: >>> Can we add a PG_lru_batch flag to determine whether a page is in lru >>> batch? >>> If we can, seems this problem will be easier. >> >> Page flags are in short supply.  You'd need a really good justification. >> > > A flag would not be able to handle the "part of multiple LRU batches" > that should currently possible (when to clear the flag?). Well, if we > have to keep supporting that. If we only to be part in a single LRU > batch, a new flag could work and we could still allow isolating a folio > from LRU while in some LRU batch. Yes, before adding a folio to LRU batch, check whether the folio has been added. Add the folio to LRU batch only if the folio has not been added. > > If we could handle it using the existing flags, that would of course be > better (wondering if we could store more information in the existing > flags by using a different encoding for the different states). If a folio contains more than one page, the folio will not be added to LRU batch. Can we use folio_test_large(folio) to filter? if (!folio_test_large(folio) && drain_allow) { lru_add_drain_all(); drain_allow = false; } > > The temporary clearing of the LRU flag we do right now tells me that > it's already not 100% reliable, so the question is how much more > unreliable we can make it before it would hurt :) >