linux-ext4 - delalloc is crippling fs

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Date:	Fri, 18 Jul 2008 11:11:30 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	ext4 development <linux-ext4@...r.kernel.org>
Subject: delalloc is crippling fs_mark performance

running fs_mark like this:

fs_mark -d /mnt/test -D 256 -n 100000 -t 4 -s 20480 -F -S 0

(256 subdirs, 100000 files/iteration, 4 threads, 20k files, no sync)

on a 1T fs, with and without delalloc (mount option), is pretty interesting:

http://people.redhat.com/esandeen/ext4/fs_mark.png

somehow delalloc is crushing performance here.  I'm planning to wait
'til the fs is full and see what the effect is on fsck, and look at the
directory layout for differences compared to w/o delalloc.

But something seems to have gone awry here ...

This is on 2.6.26 with the patch queue applied up to stable.

-Eric
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