From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0CF0A129; Sun, 3 Dec 2023 23:52:55 -0800 (PST) Received: by verein.lst.de (Postfix, from userid 2407) id 868B5227A8E; Mon, 4 Dec 2023 08:52:52 +0100 (CET) Date: Mon, 4 Dec 2023 08:52:52 +0100 From: Christoph Hellwig To: Bart Van Assche Cc: Jens Axboe , linux-block@vger.kernel.org, linux-scsi@vger.kernel.org, "Martin K . Petersen" , Christoph Hellwig Subject: Re: [PATCH v6 0/6] Disable fair tag sharing for UFS devices Message-ID: <20231204075252.GA29579@lst.de> References: <20231130193139.880955-1-bvanassche@acm.org> Precedence: bulk X-Mailing-List: linux-scsi@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: <20231130193139.880955-1-bvanassche@acm.org> User-Agent: Mutt/1.5.17 (2007-11-01) On Thu, Nov 30, 2023 at 11:31:27AM -0800, Bart Van Assche wrote: > Hi Jens, > > The fair tag sharing algorithm reduces performance for UFS devices > significantly. This is because UFS devices have multiple logical units, a > limited queue depth (32 for UFS 3.1 devices), because it happens often that > multiple logical units are accessed and also because it takes time to > give tags back after activity on a request queue has stopped. This patch series > restores UFS device performance to that of the legacy block layer by disabling > fair tag sharing for UFS devices. I feel like a broken record: fair tag sharing exists for a reason. Opting out of it for a specific driver does not make any sense. Either you can make a good argument why you don't want it at all, or for specific configurations you can clearly explain, or you make it work faster. A "treat my driver special" flag is never acceptable.