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From: Andrea Vai <andrea.vai@unipv.it>
To: Ming Lei <ming.lei@redhat.com>, "Theodore Y. Ts'o" <tytso@mit.edu>
Cc: "Schmid, Carsten" <Carsten_Schmid@mentor.com>,
	Finn Thain <fthain@telegraphics.com.au>,
	Damien Le Moal <Damien.LeMoal@wdc.com>,
	Alan Stern <stern@rowland.harvard.edu>,
	Jens Axboe <axboe@kernel.dk>,
	Johannes Thumshirn <jthumshirn@suse.de>,
	USB list <linux-usb@vger.kernel.org>,
	SCSI development list <linux-scsi@vger.kernel.org>,
	Himanshu Madhani <himanshu.madhani@cavium.com>,
	Hannes Reinecke <hare@suse.com>, Omar Sandoval <osandov@fb.com>,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	Greg KH <gregkh@linuxfoundation.org>,
	Hans Holmberg <Hans.Holmberg@wdc.com>,
	Kernel development list <linux-kernel@vger.kernel.org>,
	linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: AW: Slow I/O on USB media after commit f664a3cc17b7d0a2bc3b3ab96181e1029b0ec0e6
Date: Mon, 23 Dec 2019 15:02:35 +0100
Message-ID: <fc6f73fc5f57ade8890b472d63c7f0bd559de538.camel@unipv.it> (raw)
In-Reply-To: <20191223130828.GA25948@ming.t460p>


[-- Attachment #1: Type: text/plain, Size: 7172 bytes --]

Il giorno lun, 23/12/2019 alle 21.08 +0800, Ming Lei ha scritto:
> On Mon, Dec 23, 2019 at 12:22:45PM +0100, Andrea Vai wrote:
> > Il giorno mer, 18/12/2019 alle 17.48 +0800, Ming Lei ha scritto:
> > > On Wed, Dec 18, 2019 at 09:25:02AM +0100, Andrea Vai wrote:
> > > > Il giorno gio, 12/12/2019 alle 05.33 +0800, Ming Lei ha
> scritto:
> > > > > On Wed, Dec 11, 2019 at 11:07:45AM -0500, Theodore Y. Ts'o
> > > wrote:
> > > > > > On Wed, Dec 11, 2019 at 12:00:58PM +0800, Ming Lei wrote:
> > > > > > > I didn't reproduce the issue in my test environment, and
> > > follows
> > > > > > > Andrea's test commands[1]:
> > > > > > > 
> > > > > > >   mount UUID=$uuid /mnt/pendrive 2>&1 |tee -a $logfile
> > > > > > >   SECONDS=0
> > > > > > >   cp $testfile /mnt/pendrive 2>&1 |tee -a $logfile
> > > > > > >   umount /mnt/pendrive 2>&1 |tee -a $logfile
> > > > > > > 
> > > > > > > The 'cp' command supposes to open/close the file just
> once,
> > > > > however
> > > > > > > ext4_release_file() & write pages is observed to run for
> > > 4358
> > > > > times
> > > > > > > when executing the above 'cp' test.
> > > > > > 
> > > > > > Why are we sure the ext4_release_file() / _fput() is
> coming
> > > from
> > > > > the
> > > > > > cp command, as opposed to something else that might be
> running
> > > on
> > > > > the
> > > > > > system under test?  _fput() is called by the kernel when
> the
> > > last
> > > > > 
> > > > > Please see the log:
> > > > > 
> > > > > 
> > > 
> https://lore.kernel.org/linux-scsi/3af3666920e7d46f8f0c6d88612f143ffabc743c.camel@unipv.it/2-log_ming.zip
> > > > > 
> > > > > Which is collected by:
> > > > > 
> > > > > #!/bin/sh
> > > > > MAJ=$1
> > > > > MIN=$2
> > > > > MAJ=$(( $MAJ << 20 ))
> > > > > DEV=$(( $MAJ | $MIN ))
> > > > > 
> > > > > /usr/share/bcc/tools/trace -t -C \
> > > > >     't:block:block_rq_issue (args->dev == '$DEV') "%s %d
> %d",
> > > args-
> > > > > >rwbs, args->sector, args->nr_sector' \
> > > > >     't:block:block_rq_insert (args->dev == '$DEV') "%s %d
> %d",
> > > args-
> > > > > >rwbs, args->sector, args->nr_sector'
> > > > > 
> > > > > $MAJ:$MIN points to the USB storage disk.
> > > > > 
> > > > > From the above IO trace, there are two write paths, one is
> from
> > > cp,
> > > > > another is from writeback wq.
> > > > > 
> > > > > The stackcount trace[1] is consistent with the IO trace log
> > > since it
> > > > > only shows two IO paths, that is why I concluded that the
> write
> > > done
> > > > > via
> > > > > ext4_release_file() is from 'cp'.
> > > > > 
> > > > > [1] 
> > > > > 
> > > 
> https://lore.kernel.org/linux-scsi/320b315b9c87543d4fb919ecbdf841596c8fbcea.camel@unipv.it/2-log_ming_20191129_150609.zip
> > > > > 
> > > > > > reference to a struct file is released.  (Specifically, if
> you
> > > > > have a
> > > > > > fd which is dup'ed, it's only when the last fd
> corresponding
> > > to
> > > > > the
> > > > > > struct file is closed, and the struct file is about to be
> > > > > released,
> > > > > > does the file system's f_ops->release function get
> called.)
> > > > > > 
> > > > > > So the first question I'd ask is whether there is anything
> > > else
> > > > > going
> > > > > > on the system, and whether the writes are happening to the
> USB
> > > > > thumb
> > > > > > drive, or to some other storage device.  And if there is
> > > something
> > > > > > else which is writing to the pendrive, maybe that's why no
> one
> > > > > else
> > > > > > has been able to reproduce the OP's complaint....
> > > > > 
> > > > > OK, we can ask Andrea to confirm that via the following
> trace,
> > > which
> > > > > will add pid/comm info in the stack trace:
> > > > > 
> > > > > /usr/share/bcc/tools/stackcount
> blk_mq_sched_request_inserted
> > > > > 
> > > > > Andrew, could you collect the above log again when running
> > > new/bad
> > > > > kernel for confirming if the write done by
> ext4_release_file()
> > > is
> > > > > from
> > > > > the 'cp' process?
> > > > 
> > > > You can find the stackcount log attached. It has been produced
> by:
> > > > 
> > > > - /usr/share/bcc/tools/stackcount
> blk_mq_sched_request_inserted >
> > > trace.log
> > > > - wait some seconds
> > > > - run the test (1 copy trial), wait for the test to finish,
> wait
> > > some seconds
> > > > - stop the trace (ctrl+C)
> > > 
> > > Thanks for collecting the log, looks your 'stackcount' doesn't
> > > include
> > > comm/pid info, seems there is difference between your bcc and
> > > my bcc in fedora 30.
> > > 
> > > Could you collect above log again via the following command?
> > > 
> > > /usr/share/bcc/tools/stackcount -P -K t:block:block_rq_insert
> > > 
> > > which will show the comm/pid info.
> > 
> > ok, attached (trace_20191219.txt), the test (1 trial) took 3684
> > seconds.
> 
> From the above trace:
> 
>   b'blk_mq_sched_request_inserted'
>   b'blk_mq_sched_request_inserted'
>   b'dd_insert_requests'
>   b'blk_mq_sched_insert_requests'
>   b'blk_mq_flush_plug_list'
>   b'blk_flush_plug_list'
>   b'io_schedule_prepare'
>   b'io_schedule'
>   b'rq_qos_wait'
>   b'wbt_wait'
>   b'__rq_qos_throttle'
>   b'blk_mq_make_request'
>   b'generic_make_request'
>   b'submit_bio'
>   b'ext4_io_submit'
>   b'ext4_writepages'
>   b'do_writepages'
>   b'__filemap_fdatawrite_range'
>   b'ext4_release_file'
>   b'__fput'
>   b'task_work_run'
>   b'exit_to_usermode_loop'
>   b'do_syscall_64'
>   b'entry_SYSCALL_64_after_hwframe'
>     b'cp' [19863]
>     4400
> 
> So this write is clearly from 'cp' process, and it should be one
> ext4 fs issue.
> 
> Ted, can you take a look at this issue?
> 
> > 
> > > > I also tried the usual test with btrfs and xfs. Btrfs behavior
> > > looks
> > > > "good". xfs seems sometimes better, sometimes worse, I would
> say.
> > > I
> > > > don't know if it matters, anyway you can also find the results
> of
> > > the
> > > > two tests (100 trials each). Basically, btrfs is always
> between 68
> > > and
> > > > 89 seconds, with a cyclicity (?) with "period=2 trials". xfs
> looks
> > > > almost always very good (63-65s), but sometimes "bad" (>300s).
> > > 
> > > If you are interested in digging into this one, the following
> trace
> > > should be helpful:
> > > 
> > > 
> https://lore.kernel.org/linux-scsi/f38db337cf26390f7c7488a0bc2076633737775b.camel@unipv.it/T/#m5aa008626e07913172ad40e1eb8e5f2ffd560fc6
> > > 
> > 
> > Attached:
> > - trace_xfs_20191223.txt (7 trials, then aborted while doing the
> 8th),
> > times to complete:
> > 64s
> > 63s
> > 64s
> > 833s
> > 1105s
> > 63s
> > 64s
> 
> oops, looks we have to collect io insert trace with the following
> bcc script
> on xfs for confirming if there is similar issue with ext4, could you
> run
> it again on xfs? And only post the trace done in case of slow 'cp'.
> 
> 
> #!/bin/sh
> 
> MAJ=$1
> MIN=$2
> MAJ=$(( $MAJ << 20 ))
> DEV=$(( $MAJ | $MIN ))
> 
> /usr/share/bcc/tools/trace -t -C \
>     't:block:block_rq_issue (args->dev == '$DEV') "%s %d %d", args-
> >rwbs, args->sector, args->nr_sector' \
>     't:block:block_rq_insert (args->dev == '$DEV') "%s %d %d", args-
> >rwbs, args->sector, args->nr_sector'
> 
> 
here it is (1 trial, 313 seconds to finish)

Thanks,
Andrea

[-- Attachment #2: trace_20191223_xfs_new.zip --]
[-- Type: application/zip, Size: 129317 bytes --]

  reply index

Thread overview: 102+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [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
2019-09-18 15:25           ` Andrea Vai
2019-09-18 16:30             ` Alan Stern
2019-09-19  7:33               ` Andrea Vai
2019-09-19 17:54                 ` Alan Stern
2019-09-20  7:25                   ` Andrea Vai
2019-09-20  7:44                     ` Greg KH
2019-09-19  8:26               ` Damien Le Moal
2019-09-19  8:55                 ` Ming Lei
2019-09-19  9:09                   ` Damien Le Moal
2019-09-19  9:21                     ` Ming Lei
2019-09-19 14:01                 ` Alan Stern
2019-09-19 14:14                   ` Damien Le Moal
2019-09-20  7:03                     ` Andrea Vai
2019-09-25 19:30                       ` Alan Stern
2019-09-25 19:36                         ` Jens Axboe
2019-09-27 15:47                           ` Andrea Vai
2019-11-04 16:00                             ` Andrea Vai
2019-11-04 18:20                               ` Alan Stern
2019-11-05 11:48                                 ` Andrea Vai
2019-11-05 18:31                                   ` Alan Stern
2019-11-05 23:29                                     ` Jens Axboe
2019-11-06 16:03                                       ` Alan Stern
2019-11-06 22:13                                         ` Damien Le Moal
2019-11-07  7:04                                           ` Andrea Vai
2019-11-07  7:54                                             ` Damien Le Moal
2019-11-07 18:59                                               ` Andrea Vai
2019-11-08  8:42                                                 ` Damien Le Moal
2019-11-08 14:33                                                   ` Jens Axboe
2019-11-11 10:46                                                     ` Andrea Vai
2019-11-09 10:09                                                   ` Ming Lei
2019-11-09 22:28                                                 ` Ming Lei
2019-11-11 10:50                                                   ` Andrea Vai
2019-11-11 11:05                                                     ` Ming Lei
2019-11-11 11:13                                                       ` Andrea Vai
2019-11-22 19:16                                                   ` Andrea Vai
2019-11-23  7:28                                                     ` Ming Lei
2019-11-23 15:44                                                       ` Andrea Vai
2019-11-25  3:54                                                         ` Ming Lei
2019-11-25 10:11                                                           ` Andrea Vai
2019-11-25 10:29                                                             ` Ming Lei
2019-11-25 14:58                                                               ` Andrea Vai
2019-11-25 15:15                                                                 ` Ming Lei
2019-11-25 18:51                                                                   ` Andrea Vai
2019-11-26  2:32                                                                     ` Ming Lei
2019-11-26  7:46                                                                       ` Andrea Vai
2019-11-26  9:15                                                                         ` Ming Lei
2019-11-26 10:24                                                                           ` Ming Lei
2019-11-26 11:14                                                                           ` Andrea Vai
2019-11-27  2:05                                                                             ` Ming Lei
2019-11-27  9:39                                                                               ` Andrea Vai
2019-11-27 13:08                                                                                 ` Ming Lei
2019-11-27 15:01                                                                                   ` Andrea Vai
2019-11-27  0:21                                                                         ` Finn Thain
2019-11-27  8:14                                                                           ` AW: " Schmid, Carsten
2019-11-27 21:49                                                                             ` Finn Thain
2019-11-28  7:46                                                                             ` Andrea Vai
2019-11-28  8:12                                                                               ` AW: " Schmid, Carsten
2019-11-28 11:40                                                                                 ` Andrea Vai
2019-11-28 17:39                                                                                 ` Alan Stern
2019-11-28  9:17                                                                               ` Ming Lei
2019-11-28 17:34                                                                                 ` Andrea Vai
2019-11-29  0:57                                                                                   ` Ming Lei
2019-11-29  2:35                                                                                     ` Ming Lei
2019-11-29 14:41                                                                                       ` Andrea Vai
2019-12-03  2:23                                                                                         ` Ming Lei
2019-12-10  7:35                                                                                           ` Andrea Vai
2019-12-10  8:05                                                                                             ` Ming Lei
2019-12-11  2:41                                                                                               ` Theodore Y. Ts'o
2019-12-11  4:00                                                                                                 ` Ming Lei
2019-12-11 16:07                                                                                                   ` Theodore Y. Ts'o
2019-12-11 21:33                                                                                                     ` Ming Lei
2019-12-12  7:34                                                                                                       ` Andrea Vai
2019-12-18  8:25                                                                                                       ` Andrea Vai
2019-12-18  9:48                                                                                                         ` Ming Lei
     [not found]                                                                                                           ` <b1b6a0e9d690ecd9432025acd2db4ac09f834040.camel@unipv.it>
2019-12-23 13:08                                                                                                             ` Ming Lei
2019-12-23 14:02                                                                                                               ` Andrea Vai [this message]
2019-12-24  1:32                                                                                                                 ` Ming Lei
2019-12-24  8:04                                                                                                                   ` Andrea Vai
2019-12-24  8:47                                                                                                                     ` Ming Lei
2019-12-23 16:26                                                                                                               ` Theodore Y. Ts'o
2019-12-23 16:29                                                                                                                 ` Andrea Vai
2019-12-23 17:22                                                                                                                   ` Theodore Y. Ts'o
2019-12-23 18:45                                                                                                                     ` Andrea Vai
2019-12-23 19:53                                                                                                                       ` Theodore Y. Ts'o
2019-12-24  1:27                                                                                                                         ` Ming Lei
2019-12-24  6:49                                                                                                                           ` Andrea Vai
2019-12-24  8:51                                                                                                                           ` Andrea Vai
2019-12-24  9:35                                                                                                                             ` Ming Lei
2019-12-25  5:17                                                                                                                           ` Theodore Y. Ts'o
2019-12-26  2:27                                                                                                                             ` Ming Lei
2019-12-26  3:30                                                                                                                               ` Theodore Y. Ts'o
2019-12-26  8:37                                                                                                                                 ` Ming Lei
2020-01-07  7:51                                                                                                                                   ` Andrea Vai
     [not found]                                                                                                                                 ` <20200101074310.10904-1-hdanton@sina.com>
2020-01-01 13:53                                                                                                                                   ` slow IO on USB media Ming Lei
2019-11-29 11:44                                                                                     ` AW: Slow I/O on USB media after commit f664a3cc17b7d0a2bc3b3ab96181e1029b0ec0e6 Bernd Schubert
2019-12-02  7:01                                                                                       ` Andrea Vai
2019-11-28 17:10                                                                           ` Andrea Vai

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