Re: missing madvise functionality

Rik van Riel
2007-04-05T08:32:36Z

Eric Dumazet wrote:

> Could you please add this patch and see if it helps on your machine ?
>
> [PATCH] VM : mm_struct's mmap_cache should be close to mmap_sem
>
> Avoids cache line dirtying

I could, but I already know it's not going to help much.

How do I know this? I already have 66% idle time when running
with my patch (and without Nick Piggin's patch to take the
mmap_sem for reading only). Interestingly, despite the idle
time increasing from 10% to 66%, throughput triples...

Saving some CPU time will probably only increase the idle time,
I see no reason your patch would reduce contention and increase
throughput.

I'm not saying your patch doesn't make sense - it probably does.
I just suspect it would have zero impact on this particular
scenario, because of the already huge idle time.

--
Politics is the struggle between those who want to make their country
the best in the world, and those who believe it already is. Each group
calls the other unpatriotic.