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bh=dlYDuPOUIP5Fm/6XAmo0jwWCwPvSjNhrx8uDJ0U/ccs=; b=rTdPkiWYpMuerHdj+gIfmtQ90X0YjZB2UDkzSA/Nxoo+XrQK5kREmILQGuBQ2CiKvhNBl4 cQ7iq8tj7h/VEP/O9YhhbF/SBLJpgk+5nHV3AiuPiarpakheEBW01WUQYihVoYnc8n1tg6 oW7IaMAkaxKEr9KrvmFB61emvveMKcY= ARC-Authentication-Results: i=1; imf02.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=lst.de; spf=pass (imf02.hostedemail.com: domain of hch@lst.de designates 213.95.11.211 as permitted sender) smtp.mailfrom=hch@lst.de Received: by verein.lst.de (Postfix, from userid 2407) id 66F5568B05; Fri, 26 Jun 2026 06:22:52 +0200 (CEST) Date: Fri, 26 Jun 2026 06:22:52 +0200 From: Christoph Hellwig To: Vitaly Wool Cc: Andrew Morton , Jens Axboe , Damien Le Moal , Keith Busch , Christoph Hellwig , Sagi Grimberg , Vlastimil Babka , Harry Yoo , Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin , linux-block@vger.kernel.org, linux-nvme@lists.infradead.org, linux-mm@kvack.org, Vitaly Vul Subject: Re: [PATCH] mempool: optimize mempool resizing Message-ID: <20260626042252.GA7997@lst.de> References: <20260625194915.387663-1-vitaly.wool@konsulko.se> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260625194915.387663-1-vitaly.wool@konsulko.se> User-Agent: Mutt/1.5.17 (2007-11-01) X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 38C7080007 X-Stat-Signature: 76wokp6ruu1c749m3nmtpq9q1d3nxrii X-HE-Tag: 1782447777-992863 X-HE-Meta: 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 vHvj4pM6 HOnw38j8VYoq2tUkDtn1wAhn2kMZ4J1oC0Ilc17uqiIr57FSEGymFP2qaomi4ghhLwGZRZqEchR8SlPjSj0hMQkp9+JfY8/niR6Ikcxusg35VsyC4VMmoFrC6gQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Jun 25, 2026 at 09:49:15PM +0200, Vitaly Wool wrote: > From: Vitaly Vul > > Resizing mempool to a bigger size currently requires a new allocation and a > data copy to a new larger elements array which doesn't go well with the > idea of having a fast and deadlock free memory allocations during exreme VM > load. mempool_resize already is a very rare operations, and none of the existing callers knowns the upper bound. So what is the use case of doing this under predictable I/O load where we can't stay at the old pool size? And if you care about it, why don't you size the mempool to the max from the start?