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SubjectRe: [OSDL][BENCHMARK] Database results 2.4 versus 2.5
Cliff White <cliffw@osdl.org> wrote:
>
>
> We have found some very nice database performance improvements in the
> OSDL-DBT-2 database workload comparing the latest 2.4 kernel with 2.5.49
> on a 8-way Profusion Xeon 700MHz Pentium III system with 4GB of memory.
> We suspect there will be I/O improvements after moving to the latest
> 2.5 releases. We would like to optimize our memory utilization before
> moving on to those experiments.

So it sounds like DBT2 is stabilised now, and producing repeatable results?
That's excellent.

> ...
> We did several runs of each variant (cached and non-cached) on each of
> the two OS versions (2.4.21-pre3 and 2.5.49*). Run variances were low
> compared to the differences we saw between OS versions. Results are as
> follows (numbers represent average over the runs):

I notice you're using an extremeraid 2000? I have one of those, and
immediately shelved it when I saw how slow it is ;)

>
> Linux DBT2 Metric Wrkld %memused iostats
> Version Workload (bigger Speedup on4GB %user %sys total
> better) iops
> ___________________________________________________________________
> 2.4.21-pre3 cached 4479 99.73 74.24 3.64 **
> 2.5.49 (*) cached 5040 99.73 85.37 2.85 381
> cached 12.5%
> ___________________________________________________________________
> 2.4.21-pre3 noncached 1407.8 95.11 25.75 9.68 **
> 2.5.49 (*) noncached 1667.5 99.68 49.12 7.2 1461
> non-cached 18.4%
> ___________________________________________________________________
> ** iostats is broken at 2.4 due to driver problems.

Interesting. All the gains here are due to reduced idle time.

So either the I/O scheduler is doing a better job, or the VM page
replacement decisions are agreeable for this load.

> The %sys drops going from 2.4 to 2.5 in both cases. We suspect this is
> due to lack of paging in the 2.5 runs.

Yup. Do you have all the vmstat traces and all the other goodies? The
pgpgin/pgpgout numbers, etc seem to be wrong there.


This could easily be a complete fluke, and you may find that with
smaller/larger working sets or smaller/larger physical memory, the difference
goes away.


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