Bug 588930 - umount performance on ext4 has regressed
Summary: umount performance on ext4 has regressed
Alias: None
Product: Fedora
Classification: Fedora
Component: kernel
Version: 13
Hardware: All
OS: Linux
Target Milestone: ---
Assignee: Eric Sandeen
QA Contact: Fedora Extras Quality Assurance
Depends On:
TreeView+ depends on / blocked
Reported: 2010-05-04 20:41 UTC by Kees Cook
Modified: 2010-05-19 19:17 UTC (History)
8 users (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Clone Of:
Last Closed: 2010-05-04 21:28:49 UTC
Type: ---

Attachments (Terms of Use)

System ID Private Priority Status Summary Last Updated
Launchpad 543617 0 None None None Never
Linux Kernel 15906 0 None None None Never

Description Kees Cook 2010-05-04 20:41:39 UTC
Description of problem: umount on ext4 has seriously regressed, stalling for over a minute (or more):

Version-Release number of selected component (if applicable): 2.6.33

How reproducible: always

Steps to Reproduce:
1. install a Fedora 13, accepted defaults.
2. Run the following as root:

cd /tmp
dd if=/dev/zero of=test.ext4 bs=1 count=1 seek=1G
mkfs.ext4 -F test.ext4
mkdir -p /mnt/test
mount -o loop test.ext4 /mnt/test
echo $(seq 65536) | (cd /mnt/test; xargs touch)
time umount /mnt/test

Actual results: over a minute to perform umount.

Expected results: a few seconds.

Comment 1 Eric Sandeen 2010-05-04 21:00:36 UTC
Looks barrier related, if you change the mount -o loop to mount -o loop,nobarrier, it's speedy.

commit 68db1961bbf4e16c220ccec4a780e966bc1fece3
Author: Nikanth Karthikesan <knikanth>
Date:   Tue Mar 24 12:29:54 2009 +0100

    loop: support barrier writes
    Honour barrier requests in the loop back block device driver.
    In case of barrier bios, flush the backing file once before processing the
    barrier and once after to guarantee ordering. In case of filesystems that
    does not support fsync, barrier bios would be failed with -EOPNOTSUPP.
    Signed-off-by: Nikanth Karthikesan <knikanth>
    Signed-off-by: Jens Axboe <jens.axboe>

So you're fsyncing the loop file 2x for each barrier, and those fsyncs in turn cause cache flushes on your underlying device; once upon a time lvm didn't do anything there, but now it does ... I think you're just getting bitten by the new and improved barrier support at every level.


Comment 2 Eric Sandeen 2010-05-04 21:28:05 UTC
Since this really seems to be an upstream-relevant bug motivated by an ubuntu bug that ubuntu seemed unable to solve, I'm going to close this as UPSTREAM and worry about it there, rather than working the ubuntu bug through the fedora bugzilla.

Comment 4 Michael Neale 2010-05-11 04:37:37 UTC
The mad skillz that did the new colour schemes for a new release of an os (Ubuntu 10.04) should be just as capable at being able to overcome the limitation of journal transaction and barrier blocks between every single inode update by breakfast.

Comment 5 Fedora Update System 2010-05-17 05:39:39 UTC
kernel- has been submitted as an update for Fedora 13.

Comment 6 Fedora Update System 2010-05-19 19:17:52 UTC
kernel- has been pushed to the Fedora 13 stable repository.  If problems still persist, please make note of it in this bug report.

Note You need to log in before you can comment on or make changes to this bug.