linux-kernel - Re: Slow I/O on USB media after commit f664a3cc17b7d0a2bc3b3ab96181e1029b0ec0e6

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Date:   Sat, 23 Nov 2019 15:28:20 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     Andrea Vai <andrea.vai@...pv.it>
Cc:     Damien Le Moal <Damien.LeMoal@....com>,
        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>,
        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 Fri, Nov 22, 2019 at 08:16:30PM +0100, Andrea Vai wrote:
> Il giorno dom, 10/11/2019 alle 06.28 +0800, Ming Lei ha scritto:
> > Another thing we could try is to use 'none' via the following
> > command:
> > 
> >  echo none > /sys/block/sdh/queue/scheduler  #suppose 'sdh' points
> > to the usb storage disk
> > 
> > Because USB storage HBA is single hw queue, which depth is 1. This
> > way
> > should change to dispatch IO in the order of bio submission.
> > 
> > Andrea, could you switch io scheduler to none and update us if
> > difference
> > can be made?
> 
> Using the new kernel, there is indeed a difference because the time to
> copy a file is 1800 seconds with [mq-deadline], and 340 seconds with
> [none]. But that is still far away from the old kernel, which performs
> the copy of the same file in 76 seconds.

Please post the log of 'lsusb -v', and I will try to make a patch for
addressing the issue.


thanks, 
Ming