From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 905A12F7CE0; Wed, 2 Jul 2025 18:43:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751481793; cv=none; b=Sl6FaDd7DkNWFEhMdcHxXB2PRjW1/+6t9lX7yCWDNCf5rFapvcStwXw0VjuBqD6Cjf0Q/TXHylNexGXUpeyRVEME5bCNps+1IPsUccXRfdKforhoWDHxvQNwKGTVqC6IGcFThvz08ATFrgS5VGO7CDfwl4fmy0apqiq0ni8XAps= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751481793; c=relaxed/simple; bh=vpOtYH6IkCc3Tvi53eKq06iBzA4VwoEL2AhoYmgnNLM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=aSXyykV3JqOztuAMmb1t40AxCm/arimBW/GENDQS33eag5BgCXZ8v6dVw5rpTsbZ/6UHs7GFBwzyvj2001HUlp+qYkYIlmyGZ8J/NSsriken6t/dRMIIUPF9swjMGkGK5PGSqe6mBRnyz3A/cFtRgzi5SDhiAhCD8VGQfU+xdyk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Mp9QE6jK; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Mp9QE6jK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F0BD3C4CEE7; Wed, 2 Jul 2025 18:43:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1751481793; bh=vpOtYH6IkCc3Tvi53eKq06iBzA4VwoEL2AhoYmgnNLM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Mp9QE6jKoqnYehysrCVztxiyxSSHiGRnDH2Qhtx4fs8y0HsxQX6vvecQV5NOGuHd4 dN2C6Jg3iGlANnZCYd4TlAb9AWyMUFxItiOlq14SkSb91ODq8+5/1l1z2B1I3OgjYW F0wVh5fyeadMA5Q1lsag3eS/QqfUasaa5xBk5yWNbHmtJKsxYOJKT2d2dv28g5FNoo WZ1cAUj7G/l+tnyaZvpQoZ6hGpnmRaPA9IGCEEQlaIW44anDrsRjt8iNgxeXLUpnQX 3pwwQRHFlotk675GVhzntEDmVsQcndnhIRwdVp8CN2Kh9DCG3T+y4FCBorxXXeIfML gMcEnPfgASDQA== Date: Wed, 2 Jul 2025 11:43:12 -0700 From: "Darrick J. Wong" To: Kundan Kumar Cc: Andrew Morton , Kundan Kumar , jaegeuk@kernel.org, chao@kernel.org, viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, miklos@szeredi.hu, agruenba@redhat.com, trondmy@kernel.org, anna@kernel.org, willy@infradead.org, mcgrof@kernel.org, clm@meta.com, david@fromorbit.com, amir73il@gmail.com, axboe@kernel.dk, hch@lst.de, ritesh.list@gmail.com, dave@stgolabs.net, p.raghav@samsung.com, da.gomez@samsung.com, linux-f2fs-devel@lists.sourceforge.net, linux-fsdevel@vger.kernel.org, gfs2@lists.linux.dev, linux-nfs@vger.kernel.org, linux-mm@kvack.org, gost.dev@samsung.com Subject: Re: [PATCH 00/13] Parallelizing filesystem writeback Message-ID: <20250702184312.GC9991@frogsfrogsfrogs> References: <20250529111504.89912-1-kundan.kumar@samsung.com> <20250529203708.9afe27783b218ad2d2babb0c@linux-foundation.org> Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Wed, Jun 25, 2025 at 09:14:51PM +0530, Kundan Kumar wrote: > > > > Makes sense. It would be good to test this on a non-SMP machine, if > > you can find one ;) > > > > Tested with kernel cmdline with maxcpus=1. The parallel writeback falls > back to 1 thread behavior, showing nochange in BW. > > - On PMEM: > Base XFS : 70.7 MiB/s > Parallel Writeback XFS : 70.5 MiB/s > Base EXT4 : 137 MiB/s > Parallel Writeback EXT4 : 138 MiB/s > > - On NVMe: > Base XFS : 45.2 MiB/s > Parallel Writeback XFS : 44.5 MiB/s > Base EXT4 : 81.2 MiB/s > Parallel Writeback EXT4 : 80.1 MiB/s > > > > > Please test the performance on spinning disks, and with more filesystems? > > > > On a spinning disk, random IO bandwidth remains unchanged, while sequential > IO performance declines. However, setting nr_wb_ctx = 1 via configurable > writeback(planned in next version) eliminates the decline. > > echo 1 > /sys/class/bdi/8:16/nwritebacks > > We can fetch the device queue's rotational property and allocate BDI with > nr_wb_ctx = 1 for rotational disks. Hope this is a viable solution for > spinning disks? Sounds good to me, spinning rust isn't known for iops. Though: What about a raid0 of spinning rust? Do you see the same declines for sequential IO? --D > - Random IO > Base XFS : 22.6 MiB/s > Parallel Writeback XFS : 22.9 MiB/s > Base EXT4 : 22.5 MiB/s > Parallel Writeback EXT4 : 20.9 MiB/s > > - Sequential IO > Base XFS : 156 MiB/s > Parallel Writeback XFS : 133 MiB/s (-14.7%) > Base EXT4 : 147 MiB/s > Parallel Writeback EXT4 : 124 MiB/s (-15.6%) > > -Kundan >