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Message-ID: <BYAPR04MB5816ECD4302AD94338CB9072E77B0@BYAPR04MB5816.namprd04.prod.outlook.com>
Date: Fri, 8 Nov 2019 08:42:53 +0000
From: Damien Le Moal <Damien.LeMoal@....com>
To: Andrea Vai <andrea.vai@...pv.it>
CC: Alan Stern <stern@...land.harvard.edu>,
Jens Axboe <axboe@...nel.dk>,
Johannes Thumshirn <jthumshirn@...e.de>,
USB list <linux-usb@...r.kernel.org>,
SCSI development list <linux-scsi@...r.kernel.org>,
Himanshu Madhani <himanshu.madhani@...ium.com>,
Hannes Reinecke <hare@...e.com>,
Ming Lei <ming.lei@...hat.com>, Omar Sandoval <osandov@...com>,
"Martin K. Petersen" <martin.petersen@...cle.com>,
Greg KH <gregkh@...uxfoundation.org>,
Hans Holmberg <Hans.Holmberg@....com>,
Kernel development list <linux-kernel@...r.kernel.org>
Subject: Re: Slow I/O on USB media after commit
f664a3cc17b7d0a2bc3b3ab96181e1029b0ec0e6
On 2019/11/08 4:00, Andrea Vai wrote:
> [Sorry for the duplicate message, it didn't reach the lists due to
> html formatting]
> Il giorno gio 7 nov 2019 alle ore 08:54 Damien Le Moal
> <Damien.LeMoal@....com> ha scritto:
>>
>> On 2019/11/07 16:04, Andrea Vai wrote:
>>> Il giorno mer, 06/11/2019 alle 22.13 +0000, Damien Le Moal ha scritto:
>>>>
>>>>
>>>> Please simply try your write tests after doing this:
>>>>
>>>> echo mq-deadline > /sys/block/<name of your USB
>>>> disk>/queue/scheduler
>>>>
>>>> And confirm that mq-deadline is selected with:
>>>>
>>>> cat /sys/block/<name of your USB disk>/queue/scheduler
>>>> [mq-deadline] kyber bfq none
>>>
>>> ok, which kernel should I test with this: the fresh git cloned, or the
>>> one just patched with Alan's patch, or doesn't matter which one?
>>
>> Probably all of them to see if there are any differences.
>
> with both kernels, the output of
> cat /sys/block/sdh/queue/schedule
>
> already contains [mq-deadline]: is it correct to assume that the echo
> command and the subsequent testing is useless? What to do now?
Probably, yes. Have you obtained a blktrace of the workload during these
tests ? Any significant difference in the IO pattern (IO size and
randomness) and IO timing (any device idle time where the device has no
command to process) ? Asking because the problem may be above the block
layer, with the file system for instance.
>
> Thanks, and bye
> Andrea
>
--
Damien Le Moal
Western Digital Research
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