Re: DBT-2 anticipatory scheduler and filesystem results with 2.6.1

[markw@osdl.org]

On 19 Jan, Andrew Morton wrote:
> markw@osdl.org wrote:
>>
>>  I ran some dbt-2 tests against 5 filesystems with 2.6.1-mm4 and 2.6.1. I
>>  see a degradation from 0 to 7% in throughput. 
> 
> -mm4 also had readahead changes which will adversely impact database-style
> workloads.  I'd suggest that you revert
> 
> ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.1/2.6.1-mm4/broken-out/readahead-revert-lazy-readahead.patch
> 
> and retest.
> 
> We reverted lazy readahead because it broke NFS linear reads and was doing
> the wrong thing anyway.  We need to come up with something else for
> database-style workloads.

Ok, ran through a set of tests a -R of the
readahead-revert-lazy-readahead.patch.  Saw a significant improvement
with xfs, but the other file systems appeared to improve only marginally
compared to 2.6.1-mm4 with that patch.

Here's a summary compared to 2.6.1:

		% throughput change from 2.6.1 to 2.6.1-mm4 -R readahead
ext2		-4.9
ext3		-4.3
jfs		-5.1
reiserfs	-3.8
xfs		14.8

Here's the summary of the original 2.6.1-mm4 for reference:

		% throughput change from 2.6.1 to 2.6.1-mm4
ext2		-5.9%
ext3		-5.1%
jfs		-7.0%
reiserfs	-2.2%
xfs		-0.3%

And the link to the result details:
	http://developer.osdl.org/markw/fs/project_results.html