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SubjectQuestion regarding ext3 extents+mballoc+delalloc
Hello

Looking at ways to increase write performance on my system using ext3
Andreas Dilger pointed me to delalloc+mballoc+extent patches. Downloaded
those from ftp://ftp.clusterfs.com/pub/people/alex/2.6.16.8 and run some
benchmark, here some results using bonnie++:

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
2.6.16.19 16G 59223 91 264155 45 111459 36 57313 99 317944 63 1478 7
58814 92 276803 47 110418 36 57105 99 317534 65 1525 5
58299 92 274523 48 110290 36 56723 99 318839 65 1502 4

And here the results when mounting without extents,mballoc,delalloc option:


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
2.6.16.19 16G 38621 98 194816 94 87776 49 37921 92 239128 54 1402 5
47000 99 194276 94 89232 49 38628 92 240539 55 1399 5
45873 98 178195 90 89726 50 38482 92 240490 55 1381 4

So using delalloc+mballoc+extent gives an approx. 30% increase in performance.

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

With extents,mballoc,delalloc

5488.36 files per second 14.19 MB/s

Without extents,mballoc,delalloc

4829.84 files per second 12.72 MB/s

The performance increase is approx. 12%.

So the question is, why are these patches not included into the kernel?
I did some very extensive testing for several days and could not discover
any disadvantage using those patches. I must add that I did not test
crashes to see if data is lost. Are there any disadvantages using these
patches?

Please CC me since I am not subscribed to the list.

Thanks,
Holger
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