From: Gernot Hillier <gernot.hillier@siemens.com>
To: Theodore Ts'o <tytso@mit.edu>, Dave Chinner <david@fromorbit.com>,
linux-scsi@vger.kernel.org, MPT-FusionLinux.pdl@broadcom.com,
linux-ext4@vger.kernel.org, sathya.prakash@broadcom.com,
chaitra.basappa@broadcom.com,
suganath-prabu.subramani@broadcom.com
Subject: Re: unexpected sync delays in dpkg for small pre-allocated files on ext4
Date: Thu, 2 Jun 2016 18:23:42 +0200 [thread overview]
Message-ID: <57505D8E.6080306@siemens.com> (raw)
In-Reply-To: <20160601141218.GE5357@thunk.org>
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On 01.06.2016 16:12, Theodore Ts'o wrote:
> On Wed, Jun 01, 2016 at 03:17:14PM +0200, Gernot Hillier wrote:
>> I repeated the discussed tests and found comparable results on this machine:
>>
>> - 3 seconds dpkg install time on ext3 vs. 80 seconds for ext4
>> on same partition for same package
>> - 40 ms for fallocate+write+sync_file_range for writing a few bytes
>> - 15 ms for write+fdatasync vs. 45 ms for BLKZEROOUT on raw device
>>
>> So this seems to be not bound to one specific disk+controller setup, but
>> it still can't be a common problem affecting many people as then we
>> would see more reports about it...
>
> OK, so let's try to get common baseline, shall we?
Sure!
> I'm using as my test package:
>
> http://debug.mirrors.debian.org/debian-debug/pool/main/e/e2fsprogs/e2fsprogs-dbgsym_1.43-3_amd64.deb
[...]
> # /usr/bin/time dpkg --force-depends -i /tmp/e2fsprogs-dbgsym_1.43-3_amd64.deb
[...]
> 0.21user 0.19system 0:00.54elapsed 74%CPU (0avgtext+0avgdata 73188maxresident)k
> 0inputs+10168outputs (0major+24935minor)pagefaults 0swaps
On machine with Intel SCSI controller and on ext4 root, I see:
0.15user 0.00system 0:00.92elapsed 16%CPU (0avgtext+0avgdata
14144maxresident)k
0inputs+0outputs (0major+5447minor)pagefaults 0swaps
Installing to some ext3 partition:
0.14user 0.01system 0:00.56elapsed 26%CPU (0avgtext+0avgdata
14092maxresident)k
0inputs+0outputs (0major+5431minor)pagefaults 0swaps
This doesn't really advertise the issue as it only installs a small
number of files - yet, I still see a reproducible factor of 1.5-2 for
total elapsed time between ext3 and ext4...
> Something else would be useful is to make sure /tmp is a tmpfs mounted
> file system (so you don't get any I/O's caused by /tmp), and then do:
Ok.
> # dpkg --purge e2fsprogs-dbgsym
> # btrace /dev/sda3 > /tmp/btrace.out &
> # /usr/bin/time dpkg --force-depends -i /tmp/e2fsprogs-dbgsym_1.43-3_amd64.deb
> # kill %btrace
Please find btrace.out.bz2 attached. HTH...
Please note that I'm offline for the next couple of days, so there will
be some delay in my answers!
--
Gernot Hillier
Siemens AG, Corporate Technology
Corporate Competence Center Embedded Linux
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next prev parent reply other threads:[~2016-06-02 16:23 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <57448A5D.4050805@siemens.com>
[not found] ` <20160524231328.GB387@thunk.org>
2016-05-30 8:27 ` unexpected sync delays in dpkg for small pre-allocated files on ext4 Gernot Hillier
2016-05-31 0:21 ` Dave Chinner
2016-06-01 9:44 ` Gernot Hillier
2016-06-01 13:17 ` Gernot Hillier
2016-06-01 14:12 ` Theodore Ts'o
2016-06-02 16:23 ` Gernot Hillier [this message]
2016-07-13 13:57 ` Gernot Hillier
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