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SubjectPerformance of ext4
Hello

Doing some performance test between ext3 and ext4 I noticed that ext4
is not much faster or in some cases slower then ext3. Two years ago when
I tested ext4 it was a lot faster then ext3 (see my mail:
http://lkml.org/lkml/2006/6/6/65). Doing some simple tests with bonnie++
I got the following results:

Version 1.03 ------Sequential Output------ --Sequential Input- --Random-
-Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP
ext3(2 years ago)16G 38621 98 194816 94 87776 49 37921 92 239128 54 1402 5
16G 47000 99 194276 94 89232 49 38628 92 240539 55 1399 5
16G 45873 98 178195 90 89726 50 38482 92 240490 55 1381 4
ext3 (now) 16G 51501 97 210601 91 100479 32 55528 98 301589 44 1198 5
16G 52702 98 215540 94 99339 32 55376 97 300933 44 1159 4
16G 52426 99 212584 94 99091 31 55656 98 301669 44 1160 4

ext4(2 years ago)16G 59223 91 264155 45 111459 36 57313 99 317944 63 1478 7
16G 58814 92 276803 47 110418 36 57105 99 317534 65 1525 5
16G 58299 92 274523 48 110290 36 56723 99 318839 65 1502 4

ext4 (now) 16G 52965 98 224199 89 108440 32 56389 99 303792 42 1526 4
16G 52792 98 223980 92 107685 32 56350 98 303066 42 1532 4
16G 52994 98 222354 92 107802 32 56386 99 303727 41 1455 4

For this system the write performance is the most important factor and one
can see today ext4 is marginally faster then ext3. But 2 years ago ext4 was
a lot faster (~270MB against ~223MB).

Using my own benchmark afdbench where many process copy thousands of small
files around the results are as follows:

For ext3: 5449.76 files per second 15.58 MiB/s
For ext4: 5162.16 files per second 15.48 MiB/s

So in this test ext4 is a bit slower then ext3. Since afdbench has seen
considerable changes, one cannot compare these results with those 2 years
ago. But 2 years ago ext4 was 12% faster then ext3.

Test where done with kernel 2.6.25.4 and file system where created as follows:

ext3: mke2fs -b 4096 -m 0 -O dir_index,large_file,filetype,has_journal,sparse_super -j /dev/md7
ext4: mke2fs -b 4096 -E test_fs -m 0 -O dir_index,large_file,filetype,has_journal,sparse_super -j /dev/md7

And both where mounted with the following options:

noatime,nodiratime,commit=15

2 years ago I used 2.6.16.8 but the hardware is still the same. So what has
happened with the performance of ext4? I noticed that 2 years ago I could
use extents+mballoc+delalloc, now there is only extents+mballoc in the
current kernels. Could delalloc make the big difference? I saw that
in Andrew Morton mm tree delalloc is included. Unfortunately when I tried using
2.6.26-rc2-mm1 a sync would never return and there where lot of other
odd things, so I could not do any tests with delalloc.

So any idea what I am doing wrong or what I could do to improve those numbers?
Please CC me since I am not subscribed to the list.

Thanks,
Holger



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