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imf20.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=lst.de; spf=pass (imf20.hostedemail.com: domain of hch@lst.de designates 213.95.11.211 as permitted sender) smtp.mailfrom=hch@lst.de ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1770737940; a=rsa-sha256; cv=none; b=kRKhUTelK1OnPUEqxFxOh0mzJnvHKeefgJnvN+Tg/jfKxxItTlz6QeQQXV4Y03XXQRXPIG i+WC6wh5VqjRiyf0yOpVUp4Rw5NTro2DuRyYiVVcjw1E7WNNFVj26dlwvKVte3Kn+brGXp PwlcnjQIZsG0zJ9dyfoROj2mjG05qoY= Received: by verein.lst.de (Postfix, from userid 2407) id E3B9468CFE; Tue, 10 Feb 2026 16:38:54 +0100 (CET) Date: Tue, 10 Feb 2026 16:38:54 +0100 From: Christoph Hellwig To: Kundan Kumar Cc: Christoph Hellwig , Brian Foster , viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, willy@infradead.org, mcgrof@kernel.org, clm@meta.com, david@fromorbit.com, amir73il@gmail.com, axboe@kernel.dk, ritesh.list@gmail.com, djwong@kernel.org, dave@stgolabs.net, cem@kernel.org, wangyufei@vivo.com, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-xfs@vger.kernel.org, gost.dev@samsung.com, anuj20.g@samsung.com, vishak.g@samsung.com, joshi.k@samsung.com Subject: Re: [PATCH v3 0/6] AG aware parallel writeback for XFS Message-ID: <20260210153854.GA2484@lst.de> References: <20260116100818.7576-1-kundan.kumar@samsung.com> <20260206062527.GA25841@lst.de> <5b11145d-15e2-485c-a978-365b58854371@samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <5b11145d-15e2-485c-a978-365b58854371@samsung.com> User-Agent: Mutt/1.5.17 (2007-11-01) X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 024CC1C0006 X-Stat-Signature: gbtn9jyeh55mm9bpyy5gyiiumjych4r5 X-Rspam-User: X-HE-Tag: 1770737939-110684 X-HE-Meta: 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 /kRfo+Fq XEMfk78RGoIymwWFCi4llQWJzObPLquAoiN9sMCrZ2PKDhfDpVTyOYnT7TVOmp6sIHikrcD15mdMIgY5IdVXAfUdPPmuwETEVMBVEMLagFnCStNjFuP6kxBYNy5ngmO54SeFBGmFki4NI5UzlRaMKxWsjQXVk2DTFEztlfmsvRpYcarzaVmP97E5BvkIPbS1JYdF/ 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 Mon, Feb 09, 2026 at 09:24:49PM +0530, Kundan Kumar wrote: > - Create a bounded number of bdi wb contexts at mount time (capped, > e.g. ≤ agcount). Yeah. And then optimally map them to CPU cores, similar to the blk-mq cpumap. > - Store a per-inode stream/shard id (no per-folio state). Yes. > - Assign the stream id once and use it to select the wb context for > writeback. Yes. > - In the delalloc allocator, bias AG selection from the stream id by > partitioning AG space into per-stream "bands" and rotating the start > AG within that band; fall back to the existing allocator when > allocation can't be satisfied. Yes. We might also need something that falls back to less helpers if the free space is distributed unevently, but probably not for the first prototype.