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

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Date:   Mon, 11 Nov 2019 11:50:49 +0100
From:   Andrea Vai <andrea.vai@...pv.it>
To:     Ming Lei <ming.lei@...hat.com>
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

Il giorno dom, 10/11/2019 alle 06.28 +0800, Ming Lei ha scritto:
> On Thu, Nov 07, 2019 at 07:59:44PM +0100, 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?
> 
> 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?

Of course I would to it, but I see that with the "good" kernel the
output of "cat /sys/block/sdf/queue/scheduler" (yes, now it's sdf) is

noop deadline [cfq]

, i.e. it doesn't show "none". Does it matter? (sorry if it's a silly
question)

Thanks, and bye
Andrea