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Wong" To: Kundan Kumar Cc: Christoph Hellwig , Dave Chinner , 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, akpm@linux-foundation.org, willy@infradead.org, mcgrof@kernel.org, clm@meta.com, amir73il@gmail.com, axboe@kernel.dk, ritesh.list@gmail.com, dave@stgolabs.net, wangyufei@vivo.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, anuj20.g@samsung.com, vishak.g@samsung.com, joshi.k@samsung.com Subject: Re: [PATCH v2 00/16] Parallelizing filesystem writeback Message-ID: <20251029060932.GS4015566@frogsfrogsfrogs> References: <20251014120845.2361-1-kundan.kumar@samsung.com> <20251022043930.GC2371@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Stat-Signature: u99o7cjg9qnowuerghobu1xi3gmsncig X-Rspamd-Queue-Id: 26B2E1A0007 X-Rspamd-Server: rspam09 X-HE-Tag: 1761718174-67139 X-HE-Meta: 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 aEpc7nHD 1oRFubJHXhxNQYztkEjfu7OWax5Jhy0cHbiXRJSwOPSiVxM53UtnOjLiiq3zAkTYT20llAEqz+sPDsbMcCmK5i2L6wokeJUcOP68tWErJHgPdkdSVx+lkKqwED99/sg+wTe48oVXTr/xdWtGOHtKTYOCaewKEZ7fXUAaSclw9S51/ikN7eI69FiEyI/h4WEuTM4+GZodHpzdqjeXOLC2kbg48EHBRl7AZMjr60Ro2+mAAypVKjQ8DEUFLFdWdiA4VAU0lBkK7CVVAsEhrmb5Iy68erD7cZmdE+rXtvm+xy0J+s0ABKPbzmbhQBkO3WQUYn39w 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, Oct 29, 2025 at 11:35:21AM +0530, Kundan Kumar wrote: > On 10/22/2025 10:09 AM, Christoph Hellwig wrote: > > On Tue, Oct 21, 2025 at 09:46:30AM +1100, Dave Chinner wrote: > >> Not necessarily. The allocator can (and will) select different AGs > >> for an inode as the file grows and the AGs run low on space. Once > >> they select a different AG for an inode, they don't tend to return > >> to the original AG because allocation targets are based on > >> contiguous allocation w.r.t. existing adjacent extents, not the AG > >> the inode is located in. > > > > Also, as pointed out in the last discussion of this for the RT > > subvolume there is zero relation between the AG the inode is in > > and the data placement. > > > > > I evaluated the effect of parallel writeback on realtime inodes and > observed no improvement in IOPS. We can limit writes for realtime > inodes to utilize a single default (0) writeback context. Do you > see it differently? Was that with or without rtgroups? metadir/rtgroups aren't enabled by default yet so you'd have to select that manually with mkfs.xfs -m metadir=1. (and you might still not see much change because of what hch said) --D