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From: Andrea Vai <andrea.vai@unipv.it>
To: Jens Axboe <axboe@kernel.dk>
Cc: linux-usb@vger.kernel.org, linux-scsi@vger.kernel.org,
	Himanshu Madhani <himanshu.madhani@cavium.com>,
	Hannes Reinecke <hare@suse.com>, Ming Lei <ming.lei@redhat.com>,
	Omar Sandoval <osandov@fb.com>,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	Greg KH <gregkh@linuxfoundation.org>,
	Alan Stern <stern@rowland.harvard.edu>
Subject: Slow I/O on USB media after commit f664a3cc17b7d0a2bc3b3ab96181e1029b0ec0e6
Date: Tue, 02 Jul 2019 12:46:45 +0200
Message-ID: <cc54d51ec7a203eceb76d62fc230b378b1da12e1.camel@unipv.it> (raw)

Hi,
  I have a problem writing data to a USB pendrive, and it seems
kernel-related. With the help of Greg an Alan (thanks) and some
bisect, I found out the offending commit being

commit f664a3cc17b7d0a2bc3b3ab96181e1029b0ec0e6
Author: Jens Axboe <axboe@kernel.dk>
Date:   Thu Nov 1 16:36:27 2018 -0600

    scsi: kill off the legacy IO path
    
    This removes the legacy (non-mq) IO path for SCSI.
    
So, here I am to notify you about the problem and ask you if I can
help in any way to work it out and fix it.

The problem is that if I copy a file from the internal SATA HD to the
pendrive, it takes ~10 times to complete (in respect of the time
needed with the patch reverted).

The test script, which I use to detect if the problem triggers or not,
is:

#!/bin/bash
logfile=...
uname -a | tee -a $logfile
echo -n "Begin: " | tee -a $logfile
date | tee -a $logfile
touch inizio
SECONDS=0
mount UUID="05141239-4ea5-494d-aa91-acd67db89ce5" /mnt/pendrive
cp /NoBackup/buttare/testfile /mnt/pendrive
umount /mnt/pendrive
tempo=$SECONDS
touch fine
echo -n "...end: " | tee -a $logfile
date | tee -a $logfile
echo "It took $tempo seconds!" | tee -a $logfile

If I run the test with a 512MB file it takes >10min vs. half a minute.

The problem is still present in last tested git (cloned today in the
morning).

You can see the previous discussion that lead to these results at

https://marc.info/?t=155922230700001&r=1&w=2

Thanks, and bye
Andrea


             reply index

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-02 10:46 Andrea Vai [this message]
2019-07-02 11:51 ` Johannes Thumshirn
2019-07-02 22:36   ` Andrea Vai
2019-07-03  7:29     ` Johannes Thumshirn
2019-07-03 14:23       ` Alan Stern
2019-07-06 22:06         ` Andrea Vai
2019-07-08 15:38           ` Alan Stern
2019-07-02 12:01 ` Ming Lei
2019-07-02 22:39   ` Andrea Vai
2019-07-03  2:01     ` Ming Lei
2019-07-03  5:11       ` Andrea Vai
2019-07-03  6:36         ` Ming Lei
2019-07-03 15:27           ` Chris Murphy
2019-07-06  9:33           ` Andrea Vai
2019-07-08  1:01             ` Ming Lei
2019-07-09 21:18               ` Andrea Vai
2019-07-10  2:44                 ` Ming Lei
     [not found] <e3f87757f7a0fdf551e911ad32fc8122eebe04c7.camel@unipv.it>
2019-08-13 19:52 ` Alan Stern
     [not found] <307581a490b610c3025ee80f79a465a89d68ed19.camel@unipv.it>
2019-08-20 17:13 ` Alan Stern
2019-08-23 10:39   ` Andrea Vai
2019-08-23 20:42     ` Alan Stern
2019-08-26  6:09       ` Andrea Vai
2019-08-26 16:33         ` Alan Stern

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