Messages in this thread |  | | Date | Fri, 9 Nov 2001 11:05:32 +1100 | From | Anton Blanchard <> | Subject | Re: speed difference between using hard-linked and modular drives? |
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> > we should fix this by trying to allocate continuous physical memory if > > possible, and fall back to vmalloc() only if this allocation fails. > > Check -aa. A patch to do that has been in there for some time now.
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.
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