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

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Date:   Mon, 25 Nov 2019 23:15:35 +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 Mon, Nov 25, 2019 at 03:58:34PM +0100, Andrea Vai wrote:
> Il giorno lun, 25/11/2019 alle 18.29 +0800, Ming Lei ha scritto:
> > On Mon, Nov 25, 2019 at 11:11:00AM +0100, Andrea Vai wrote:
> > > Il giorno lun, 25/11/2019 alle 11.54 +0800, Ming Lei ha scritto:
> > > > On Sat, Nov 23, 2019 at 04:44:55PM +0100, Andrea Vai wrote:
> > > > > Il giorno sab, 23/11/2019 alle 15.28 +0800, Ming Lei ha
> > scritto:
> > > > > > 
> > > > > > Please post the log of 'lsusb -v', and I will try to make a
> > > > patch
> > > > > > for
> > > > > > addressing the issue.
> > > > > 
> > > > > attached,
> > > > 
> > > > Please apply the attached patch, and re-build & install & reboot
> > > > kernel.
> > > > 
> > > > This time, please don't switch io scheduler.
> > > 
> > > # patch -p1 < usb.patch outputs:
> > > 
> > > (Stripping trailing CRs from patch; use --binary to disable.)
> > > patching file block/blk-mq.c
> > > Hunk #1 succeeded at 1465 (offset 29 lines).
> > > Hunk #2 succeeded at 3061 (offset 13 lines).
> > > (Stripping trailing CRs from patch; use --binary to disable.)
> > > patching file drivers/scsi/scsi_lib.c
> > > Hunk #1 succeeded at 1902 (offset -37 lines).
> > > (Stripping trailing CRs from patch; use --binary to disable.)
> > > patching file drivers/usb/storage/scsiglue.c
> > > Hunk #1 succeeded at 651 (offset -10 lines).
> > > (Stripping trailing CRs from patch; use --binary to disable.)
> > > patching file include/linux/blk-mq.h
> > > Hunk #1 succeeded at 226 (offset -162 lines).
> > > (Stripping trailing CRs from patch; use --binary to disable.)
> > > patching file include/scsi/scsi_host.h
> > > patch unexpectedly ends in middle of line
> > > patch unexpectedly ends in middle of line
> > > 
> > > Just to be sure I have to go on, is this correct? Sounds like an
> > error
> > > but I don't know if it is important.
> > 
> > Looks there is small conflict, however it has been fixed by patch,
> > so
> > it is correct, please go on your test.
> 
> Done, it still fails (2000 seconds or more to copy 1GB) :-(
> 
> cat /sys/block/sdf/queue/scheduler outputs:
> [mq-deadline] none
> 
> What to try next?

1) cat /sys/kernel/debug/block/$DISK/hctx0/flags

note: replace $DISK with disk name of your usb drive, such as, if it is
/dev/sdb, pass $DISK as sdb.

2) echo 128 > /sys/block/$DISK/queue/nr_requests and run your copy 1GB
test again.


Thanks, 
Ming