reaim - 2.6.3-mm1 IO performance down.

[cliff white <cliffw@osdl.org>]

Running the reaim 'new_fserver' workload, we now see a performance drop
on 2.6.3-mm1, ext3 filesystem

Kernel          JPM       Max Users     Percent change
inux-2.6.3      10347.87  172           0.0
2.6.3-rc3-mm1   9826.35   164           -5.07
2.6.3-mm1       8938.17   140   (run 1) -13.65
2.6.3-mm1       9100.39   136    (run 2)-12.08 

I have done some comparions graphs here, with readprofile data:
http://developer.osdl.org/cliffw/reaim/compares/r_comp/2.6.3_vs_mm1_r1/index.html
http://developer.osdl.org/cliffw/reaim/compares/r_comp/2.6.3_vs_mm1_r2/index.html

The interesting graph is the bottom one on the page, comparing client
run-time to number of children. The -mm1 kernel has a spike in run time, becoming
very noticealbe around 60-80 lusers.

kernel       Users 	JPM        Run Time
linux-2.6.3  60         10327.87   34.16 seconds
2.6.3-mm1    60         8279.75    42.61 seconds

Linux-2.6.3  80         10275.23   45.78 seconds
2.6.3-mm1    80         7841.31    59.99 seconds


For the same test on the same machine, results from 2.6.2-rc1-mm2 and 2.6.2-rc3-mm1
were within 1.0% of the linux-2.6.2 runs. So this is new. 

More data and tests if requested - are there some patch sets we should try reverting?
cliffw

-- 
The church is near, but the road is icy.
The bar is far, but i will walk carefully. - Russian proverb