From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 04E1022B8AB; Tue, 10 Feb 2026 15:38:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.95.11.211 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770737940; cv=none; b=tTFg0zCFrdKF7fKvhszK5R8orKGRiQM9loo3OKaTfbo860XVKBwgC5Av5j7qBjQEwtziof3y4nahlnW7nFjZqE7bzVkHDhEqQSPSP35umReKZJCZlK33UUl0JiyO8WqO7e0WXqI4VWj9p6wz5oIEvBEGFMpPPhOeudCRI/JoRW4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770737940; c=relaxed/simple; bh=uFcjjkA3WFiZqFMy3mxET9pV3Rhqx7NQjS+2SqxHlZM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Qvn/xpIfGnXwDPdB7P1WlEL1PlGoa3iAhjM/WfmVyOxiVVvJuFyNnV7PjkncyIuJB3R7JkKajZLTxEW/0L9kkhD9tHq4MJkn/zvC7/o9QtXn1QW3V7eTkGIachb4aE6pt08y319OY9BPI7ErGQvdNkGRMhAYXpae2Qg2KuKtO9M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=lst.de; spf=pass smtp.mailfrom=lst.de; arc=none smtp.client-ip=213.95.11.211 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=lst.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=lst.de 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> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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) 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.