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From: Ming Lei <ming.lei@redhat.com>
To: "Theodore Y. Ts'o" <tytso@mit.edu>
Cc: Andrea Vai <andrea.vai@unipv.it>,
	"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: Wed, 11 Dec 2019 12:00:58 +0800
Message-ID: <20191211040058.GC6864@ming.t460p> (raw)
In-Reply-To: <20191211024137.GB61323@mit.edu>

On Tue, Dec 10, 2019 at 09:41:37PM -0500, Theodore Y. Ts'o wrote:
> On Tue, Dec 10, 2019 at 04:05:50PM +0800, Ming Lei wrote:
> > > > The path[2] is expected behaviour. Not sure path [1] is correct,
> > > > given
> > > > ext4_release_file() is supposed to be called when this inode is
> > > > released. That means the file is closed 4358 times during 1GB file
> > > > copying to usb storage.
> > > > 
> > > > [1] insert requests when returning to user mode from syscall
> > > > 
> > > >   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'
> > > >     4358
> 
> I'm guessing that your workload is repeatedly truncating a file (or
> calling open with O_TRUNC) and then writing data to it.  When you do
> this, then when the file is closed, we assume that since you were
> replacing the previous contents of a file with new contents, that you
> would be unhappy if the file contents was replaced by a zero length
> file after a crash.  That's because ten years, ago there were a *huge*
> number of crappy applications that would replace a file by reading it
> into memory, truncating it, and then write out the new contents of the
> file.  This could be a high score file for a game, or a KDE or GNOME
> state file, etc.
> 
> So if someone does open, truncate, write, close, we still immediately
> writing out the data on the close, assuming that the programmer really
> wanted open, truncate, write, fsync, close, but was too careless to
> actually do the right thing.
> 
> Some workaround[1] like this is done by all of the major file systems,
> and was fallout the agreement from the "O_PONIES"[2] controversy.
> This was discussed and agreed to at the 2009 LSF/MM workshop.  (See
> the "rename, fsync, and ponies" section.)
> 
> [1] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/317781/comments/45
> [2] https://blahg.josefsipek.net/?p=364
> [3] https://lwn.net/Articles/327601/
> 
> So if you're seeing a call to filemap_fdatawrite_range as the result
> of a fput, that's why.
> 
> In any case, this behavior has been around for a decade, and it
> appears to be incidental to your performance difficulties with your
> USB thumbdrive and block-mq.

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.


[1] https://marc.info/?l=linux-kernel&m=157486689806734&w=2


Thanks,
Ming


  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 [this message]
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
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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