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imf30.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=lst.de; spf=pass (imf30.hostedemail.com: domain of hch@lst.de designates 213.95.11.211 as permitted sender) smtp.mailfrom=hch@lst.de ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1791982989; b=uOoJoqAwlbTRVKvQZRQqi6j8vOalM+ZKVR0lLpIVNF7vzdJy2s9xaIb1JaGkdekXuAU5E8 HB/kVbcc28vj/k9S3NG/G+apqB7LvfxFLti9BWPFsnwhI5bkbO2GhFCUT8TyXb8gcyoMqr zJFHdX/Lo6h4HMfE084CxQiDuwiP2to= Received: by verein.lst.de (Postfix, from userid 2407) id 8FF64227A88; Wed, 14 Oct 2026 15:03:02 +0200 (CEST) Date: Wed, 14 Oct 2026 15:03:01 +0200 From: Christoph Hellwig To: Vitaly Wool Cc: Harry Yoo , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Roman Gushchin , David Rientjes , Christoph Lameter , Hao Li , Andrew Morton , Vlastimil Babka , Damien Le Moal , Christoph Hellwig , vitaly.vul@partner.samsung.com Subject: Re: [PATCH] mempool: optimize mempool resizing Message-ID: <20261014130301.GC15407@lst.de> References: <20261013091408.1231786-1-vitaly.wool@konsulko.se> <20261014084528.1280968-1-vitaly.wool@konsulko.se> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261014084528.1280968-1-vitaly.wool@konsulko.se> User-Agent: Mutt/1.5.17 (2007-11-01) X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: C87678001C X-Rspam-User: X-Stat-Signature: e7hqd7stgwk9sub1r5mx6jaxeku615qd X-HE-Tag: 1791982988-991648 X-HE-Meta: U2FsdGVkX1++BNMOh2+SBhx4rUbD63mfFcerdwuyMYzqr4DsW5OSCANjWF35lSdlRUReQdvQ/HfQCn2qwInVOnWpS43SXY5OMGyLC4U1nwz+syea42YKDhIj7fDMB+aSKF9Jf+CqAE4oZgqpZJF691+tqavCz9yHXQKtBvBjnsNAPQRwp74nu+l/DZ31Y9V70avekXwqWh/iM7TNz91eyiwc/DDhQ0EjPZvM9KJYSePGhgExRV1FgWWiEFnQ7cYuul7lo0n4dnIVx9jI1sgTd9USeNJzAoV2hi2nrJlwXfVcVgJ0wfcvQ6dicyo44ny3HQDqLbKf9LCAK5twNm7hr1CciovOCh8X0m0y4J+4TKEM1iEopmocrEVhL8VmTr1ildBEDX9owyaoI7YPNwrqmbzXwlRI/BgNQS7ckBe50jM79SNU2WCcvUcdsComojNLi3z934M9hVHCtTQipljsF1c6N8UVjuVPYL2ZJZ7oN2LzATte4iqQRoKny6Qxxx1dcd+L48TgPwg5wsBr0AtJFWe8INbgjgEYFeFgS+mFR9SMBYJiixCdnhbaptyYGqujJT2ytr8taG+wvQqTNStm/AFSeFQCiEBW2vcwqWwDMzGc4IWYcfPlK1Q8iHwCTmxRhXJy7p1uJBFDm/wcom3x43mOfwjwk7/FLxr4F1aLeD5Lg1FoTPECtV2XCvb8VpK1EvNBqjUBPdNvkSTfd+pqzSV2UlIS85hw3eOPmJzUd/JbI61q/32XVWJmtZK1+8eNF8Wqz8xgSO5PwQO2aUAN40d45zFJx3ek858Q4CxsdFizamYSWyxL0ZyWTFT960YtHcjt/94X40DVHXuSID1tuXf0HzvzepeJIzMk0YETtiOGcWaLzw0MNTD+o0k6wjHEMrbLeUUGwH/3Qwyuy0J/WNkOAGdWXh93o0ySwukzgGWZjBAclxEfiza0Iii2xIDsM24N2xMWF0NHWJrL/gI lPWfOzI3 WvFS5/r6PYUQeKpXZ/FOfczO1krvkZkI6sQlAuE5hW2myhqLptIUFbAQFzcepdpTygYxxV1NTHrjb77HCcz+dCBE1f2fe0zgdly5SekswKfiYBoL5UCbqVuqcdw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Oct 14, 2026 at 10:45:28AM +0200, Vitaly Wool wrote: > We are using mempool to store a large set of preallocated rather big buffers. In case > of memory pressure we'd call mempool_resize() (via shrinker callbacks) to reduce the > amount of memory occupied by that set, and when the situation stabilizes, we'd go back > to the original set again. > > Imagine you have a mempool with 10000 elements, and you have to reduce it to 3000. Then > if you at some point want to go back to 10000, you'll end up reallocating the elements Who is "we" and where is the code? This is a highly unusual, not to say most like broken usage of mempools. If you need changes to support such a use case you should include a link to the intree user (or bundle it with the submission of the new code).