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([2620:10d:c090:180::d575]) by smtp.gmail.com with ESMTPSA id j4sm492799pjf.25.2019.11.05.15.29.20 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 05 Nov 2019 15:29:22 -0800 (PST) Subject: Re: Slow I/O on USB media after commit f664a3cc17b7d0a2bc3b3ab96181e1029b0ec0e6 To: Alan Stern , Andrea Vai Cc: Damien Le Moal , Johannes Thumshirn , USB list , SCSI development list , Himanshu Madhani , Hannes Reinecke , Ming Lei , Omar Sandoval , "Martin K. Petersen" , Greg KH , Hans Holmberg , Kernel development list References: From: Jens Axboe Message-ID: <61033407-731e-8cf5-8590-b07e2567693a@kernel.dk> Date: Tue, 5 Nov 2019 16:29:18 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On 11/5/19 11:31 AM, Alan Stern wrote: > On Tue, 5 Nov 2019, Andrea Vai wrote: > >> Il giorno lun, 04/11/2019 alle 13.20 -0500, Alan Stern ha scritto: > >>> You should be able to do something like this: >>> >>> cd linux >>> patch -p1 >> >>> and that should work with no errors. You don't need to use git to >>> apply a patch. >>> >>> In case that patch2 file was mangled somewhere along the way, I >>> have >>> attached a copy to this message. >> >> Ok, so the "patch" command worked, the kernel compiled and ran, but >> the test still failed (273, 108, 104, 260, 177, 236, 179, 1123, 289, >> 873 seconds to copy a 500MB file, vs. ~30 seconds with the "good" >> kernel). >> >> Let me know what else could I do, > > I'm out of suggestions. If anyone else knows how to make a kernel with > no legacy queuing support -- only multiqueue -- issue I/O requests > sequentially, please speak up. Do we know for a fact that the device needs strictly serialized requests to not stall? And writes in particular? I won't comment on how broken that is, just trying to establish this as the problem that's making this particular device be slow? I've lost track of this thread, but has mq-deadline been tried as the IO scheduler? We do have support for strictly serialized (writes) since that's required for zoned device, wouldn't be hard at all to make this cover a blacklisted device like this one. > In the absence of any responses, after a week or so I will submit a > patch to revert the f664a3cc17b7 ("scsi: kill off the legacy IO path") > commit. That's not going to be feasible. -- Jens Axboe