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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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: 686z4msf75dq7ncradfed3ssdtx47c1x X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 1A8B21C000B X-Rspam-User: X-HE-Tag: 1751481793-490388 X-HE-Meta: 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 3nbxM48w DxrXWeYKoAJSNxTg5tpqyQb+Dei9tU3lxCOx6nRopK1jpN7I0Yxqj8Fi84/JRgz6SupJln0+rSDFJh2K8wVyb05gA6BUau8JyWGf/0PAoDDLwUK65wXFRlFhP6UN51wv7YQJp3gYJTdHEjcpvfOAfkC04ZfU90M2jW+C4OeQIfHpza9xRIfjh6KZEth3UuhmHGmUngtMALuvWm/K7Ijrvftrpsz1PiSlikogWCf9/J5Gc066Z9ob3XdpJ7pH+V+JzdJY11ZOgTXujSqJGSselMUCFsC/MVciKMFYedQQNLz/0Wth1CTv3Klo0dJirpVs10qg/ 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 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 >