signifanctly slowdown of FreeBSD 8.0-CURRENT/amd64

[Attilio Rao]

2009/6/24 Randall Stewart <rrs at lakerest.net>:
> One thing I have noticed for a while.. and have not
> been able to track down..
>
> If one runs
>
> /usr/src/tools/tools/syscall_timing/syscall_timing
>
> On a 7.2 kernel and compare it on the same machine to an 8.0 kernel
> you will see almost a 3x slow down in 8.

So, as long as I think that for the pressing, next release, it is very
important to track such regressions down, I hope both Pierre and
Randall want to lend an hand.

First thing, Randall, could you recompile your kernel with
HWPMC_HOOKS, device hwpmc, and do some pmcstat runs in order to see
where/how the slowdown happens?
For example you could check if the number of cache misses increases, or similar.

Both could provide, instead, once the slowdown takes place, verbose
top, ps and possibly vmstat, just to be sure in case.

If you are unable to reproduce the slowdown or give an hand, please let me know.

Thanks,
Attilio


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