From: Theodore Ts'o <tytso@mit.edu>
To: Gernot Hillier <gernot.hillier@siemens.com>
Cc: 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: Wed, 1 Jun 2016 10:12:18 -0400 [thread overview]
Message-ID: <20160601141218.GE5357@thunk.org> (raw)
In-Reply-To: <574EE05A.9070302@siemens.com>
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? I'm using as my
test package:
http://debug.mirrors.debian.org/debian-debug/pool/main/e/e2fsprogs/e2fsprogs-dbgsym_1.43-2_amd64.deb
% ls -s /tmp/e2fsprogs-dbgsym_1.43-3_amd64.deb
1108 /tmp/e2fsprogs-dbgsym_1.43-3_amd64.deb
% md5sum /tmp/e2fsprogs-dbgsym_1.43-3_amd64.deb
148ee631f46ed2e05a17faf36cc9d630 /tmp/e2fsprogs-dbgsym_1.43-3_amd64.deb
# dpkg --purge e2fsprogs-dbgsym
(Reading database ... 322967 files and directories currently installed.)
Removing e2fsprogs-dbgsym (1.43-3) ...
# /usr/bin/time dpkg --force-depends -i /tmp/e2fsprogs-dbgsym_1.43-3_amd64.deb
Selecting previously unselected package e2fsprogs-dbgsym.
(Reading database ... 322947 files and directories currently installed.)
Preparing to unpack .../e2fsprogs-dbgsym_1.43-3_amd64.deb ...
Unpacking e2fsprogs-dbgsym (1.43-3) ...
Setting up e2fsprogs-dbgsym (1.43-3) ...
0.21user 0.19system 0:00.54elapsed 74%CPU (0avgtext+0avgdata 73188maxresident)k
0inputs+10168outputs (0major+24935minor)pagefaults 0swaps
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:
# 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
Replace /dev/sda3 with the device name of your root partition, and
then send us the compressed btrace.out file, which might give us a
clue about what is going on.
Cheers,
- Ted
next prev parent reply other threads:[~2016-06-01 14:12 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 [this message]
2016-06-02 16:23 ` Gernot Hillier
2016-07-13 13:57 ` Gernot Hillier
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