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[49.180.91.142]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-7992d0e2774sm19762406b3a.63.2025.10.15.13.49.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Oct 2025 13:49:23 -0700 (PDT) Received: from dave by dread.disaster.area with local (Exim 4.98.2) (envelope-from ) id 1v98Qy-0000000FJEJ-1QPI; Thu, 16 Oct 2025 07:49:20 +1100 Date: Thu, 16 Oct 2025 07:49:20 +1100 From: Dave Chinner To: Christoph Hellwig Cc: Christian Brauner , Jan Kara , Carlos Maiolino , Andrew Morton , willy@infradead.org, dlemoal@kernel.org, hans.holmberg@wdc.com, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-xfs@vger.kernel.org Subject: Re: [PATCH 2/3] writeback: allow the file system to override MIN_WRITEBACK_PAGES Message-ID: References: <20251015062728.60104-1-hch@lst.de> <20251015062728.60104-3-hch@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251015062728.60104-3-hch@lst.de> X-Stat-Signature: ty5c8wr6zumm96mypyuaxrej1mfd6qba X-Rspamd-Queue-Id: 06024C0006 X-Rspamd-Server: rspam06 X-Rspam-User: X-HE-Tag: 1760561367-252583 X-HE-Meta: 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 eKf0I/4v 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 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 15, 2025 at 03:27:15PM +0900, Christoph Hellwig wrote: > The relatively low minimal writeback size of 4MiB leads means that > written back inodes on rotational media are switched a lot. Besides > introducing additional seeks, this also can lead to extreme file > fragmentation on zoned devices when a lot of files are cached relative > to the available writeback bandwidth. > > Add a superblock field that allows the file system to override the > default size. Hmmm - won't changing this for the zoned rtdev also change behaviour for writeback on the data device? i.e. upping the minimum for the normal data device on XFS will mean writeback bandwidth sharing is a lot less "fair" and higher latency when we have a mix of different file sizes than it currently is... -Dave. -- Dave Chinner david@fromorbit.com