Re: [Lse-tech] [patch] sched-domain cleanups, sched-2.6.5-rc2-mm2-A3

Martin J. Bligh
2004-03-25T19:25:42Z

>> It doesn't do load balance in wake_up_forked_process() and is
>> relatively non aggressive in balancing later. This leads to the
>> multithreaded OpenMP STREAM running its childs first on the same node
>> as the original process and allocating memory there. [...]
>
> i believe the fix we want is to pre-balance the context at fork() time.
> I've implemented this (which is basically just a reuse of
> sched_balance_exec() in fork.c, and the related namespace cleanups),
> could you give it a go:
>
> http://redhat.com/~mingo/scheduler-patches/sched-2.6.5-rc2-mm2-A5
>
> another solution would be to add SD_BALANCE_FORK.
>
> also, the best place to do fork() blancing is not at
> wake_up_forked_process() time, but prior doing the MM copy. This patch
> does it there. At wakeup time we've already copied all the pagetables
> and created tons of dirty cachelines.

How are you going to decide whether to rebalance at fork time or exec time?
Exec time balancing is a *lot* more efficient, it just doesn't work for
things that don't exec ... cloned threads would certainly be one case.

M.