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From: Ming Lei <ming.lei@redhat.com>
To: Andrea Vai <andrea.vai@unipv.it>
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>
Subject: Re: AW: Slow I/O on USB media after commit f664a3cc17b7d0a2bc3b3ab96181e1029b0ec0e6
Date: Fri, 29 Nov 2019 10:35:55 +0800	[thread overview]
Message-ID: <20191129023555.GA8620@ming.t460p> (raw)
In-Reply-To: <20191129005734.GB1829@ming.t460p>

On Fri, Nov 29, 2019 at 08:57:34AM +0800, Ming Lei wrote:
> On Thu, Nov 28, 2019 at 06:34:32PM +0100, Andrea Vai wrote:
> > Il giorno gio, 28/11/2019 alle 17.17 +0800, Ming Lei ha scritto:
> > > On Thu, Nov 28, 2019 at 08:46:57AM +0100, Andrea Vai wrote:
> > > > Il giorno mer, 27/11/2019 alle 08.14 +0000, Schmid, Carsten ha
> > > > scritto:
> > > > > > 
> > > > > > > Then I started another set of 100 trials and let them run
> > > > > tonight, and
> > > > > > > the first 10 trials were around 1000s, then gradually
> > > decreased
> > > > > to
> > > > > > > ~300s, and finally settled around 200s with some trials
> > > below
> > > > > 70-80s.
> > > > > > > This to say, times are extremely variable and for the first
> > > time
> > > > > I
> > > > > > > noticed a sort of "performance increase" with time.
> > > > > > >
> > > > > > 
> > > > > > The sheer volume of testing (probably some terabytes by now)
> > > would
> > > > > > exercise the wear leveling algorithm in the FTL.
> > > > > > 
> > > > > But with "old kernel" the copy operation still is "fast", as far
> > > as
> > > > > i understood.
> > > > > If FTL (e.g. wear leveling) would slow down, we would see that
> > > also
> > > > > in
> > > > > the old kernel, right?
> > > > > 
> > > > > Andrea, can you confirm that the same device used with the old
> > > fast
> > > > > kernel is still fast today?
> > > > 
> > > > Yes, it is still fast. Just ran a 100 trials test and got an
> > > average
> > > > of 70 seconds with standard deviation = 6 seconds, aligned with
> > > the
> > > > past values of the same kernel.
> > > 
> > > Then can you collect trace on the old kernel via the previous
> > > script?
> > > 
> > > #!/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'
> > > 
> > > Both the two trace points and bcc should be available on the old
> > > kernel.
> > > 
> > 
> > Trace attached. Produced by: start the trace script
> > (with the pendrive already plugged), wait some seconds, run the test
> > (1 trial, 1 GB), wait for the test to finish, stop the trace.
> > 
> > The copy took 73 seconds, roughly as already seen before with the fast
> > old kernel.
> 
> This trace shows a good write IO order because the writeback IOs are
> queued to block layer serially from the 'cp' task and writeback wq.
> 
> However, writeback IO order is changed in current linus tree because
> the IOs are queued to block layer concurrently from the 'cp' task
> and writeback wq. It might be related with killing queue_congestion
> by blk-mq.
> 
> The performance effect could be not only on this specific USB drive,
> but also on all HDD., I guess.
> 
> However, I still can't reproduce it in my VM even though I built it
> with similar setting of Andrea's test machine. Maybe the emulated disk
> is too fast than Andrea's.
> 
> Andrea, can you collect the following log when running the test
> on current new(bad) kernel?
> 
> 	/usr/share/bcc/tools/stackcount  -K blk_mq_make_request

Instead, please run the following trace, given insert may be
called from other paths, such as flush plug:

	/usr/share/bcc/tools/stackcount -K t:block:block_rq_insert

If you are using python3, the following failure may be triggered:

	"cannot use a bytes pattern on a string-like object"

Then apply the following fix on /usr/lib/python3.7/site-packages/bcc/__init__.py

diff --git a/src/python/bcc/__init__.py b/src/python/bcc/__init__.py
index 6f114de8..bff5f282 100644
--- a/src/python/bcc/__init__.py
+++ b/src/python/bcc/__init__.py
@@ -769,7 +769,7 @@ class BPF(object):
                 evt_dir = os.path.join(cat_dir, event)
                 if os.path.isdir(evt_dir):
                     tp = ("%s:%s" % (category, event))
-                    if re.match(tp_re, tp):
+                    if re.match(tp_re.decode(), tp):
                         results.append(tp)
         return results

Thanks,
Ming


  reply	other threads:[~2019-11-29  2:36 UTC|newest]

Thread overview: 102+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <307581a490b610c3025ee80f79a465a89d68ed19.camel@unipv.it>
2019-08-20 17:13 ` Slow I/O on USB media after commit f664a3cc17b7d0a2bc3b3ab96181e1029b0ec0e6 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 [this message]
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
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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