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[49.181.60.96]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-740590a463fsm9917368b3a.173.2025.05.06.14.46.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 06 May 2025 14:46:04 -0700 (PDT) Received: from dave by dread.disaster.area with local (Exim 4.98.2) (envelope-from ) id 1uCQ6z-00000000GTQ-0jbm; Wed, 07 May 2025 07:46:01 +1000 Date: Wed, 7 May 2025 07:46:01 +1000 From: Dave Chinner To: Anton Gavriliuk Cc: Laurence Oberman , linux-nvme@lists.infradead.org, linux-xfs@vger.kernel.org, linux-block@vger.kernel.org Subject: Re: Sequential read from NVMe/XFS twice slower on Fedora 42 than on Rocky 9.5 Message-ID: References: <7c33f38a52ccff8b94f20c0714b60b61b061ad58.camel@redhat.com> Precedence: bulk X-Mailing-List: linux-xfs@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 Tue, May 06, 2025 at 02:03:37PM +0300, Anton Gavriliuk wrote: > > So is this MD chunk size related? i.e. what is the chunk size > > the MD device? Is it smaller than the IO size (256kB) or larger? > > Does the regression go away if the chunk size matches the IO size, > > or if the IO size vs chunk size relationship is reversed? > > According to the output below, the chunk size is 512K, Ok. `iostat -dxm 5` output during the fio run on both kernels will give us some indication of the differences in IO patterns, queue depths, etc. Silly question: if you use DM to create the same RAID 0 array with a dm table such as: 0 75011629056 striped 12 1024 /dev/nvme7n1 0 /dev/nvme0n1 0 .... /dev/nvme12n1 0 to create a similar 38TB raid 0 array, do you see the same perf degradation? -Dave. -- Dave Chinner david@fromorbit.com