Re: speed difference between using hard-linked and modular drives?

Andi Kleen
2001-11-09T05:46:03Z

On Fri, Nov 09, 2001 at 11:05:32AM +1100, Anton Blanchard wrote:
> We also need a way to satisfy very large allocations for the hashes (eg
> the pagecache hash). On a 32G machine we get awful performance on the
> pagecache hash because we can only get an order 9 allocation out of
> get_free_pages:
>
> http://samba.org/~anton/linux/pagecache/pagecache_before.png
>
> When switching to vmalloc the hash is large enough to be useful:
>
> http://samba.org/~anton/linux/pagecache/pagecache_after.png
>
> As pointed out by Davem and Ingo we should try and avoid vmalloc here
> due to tlb trashing.

Sounds like you need a better hash function instead.

-Andi