Messages in this thread |  | | Date | Thu, 08 Nov 2001 23:16:32 -0800 (PST) | Subject | Re: speed difference between using hard-linked and modular drives? | From | "David S. Miller" <> |
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From: Andi Kleen <ak@suse.de> Date: Fri, 9 Nov 2001 07:39:46 +0100
I'm assuming that walking on average 5-10 pages on a lookup is not too big a deal, especially when you use prefetch for the list walk.
Oh no, not this again...
It _IS_ a big deal. Fetching _ONE_ hash chain cache line is always going to be cheaper than fetching _FIVE_ to _TEN_ page struct cache lines while walking the list.
Even if prefetch would kill all of this overhead (sorry, it won't), it is _DUMB_ and _STUPID_ to bring those _FIVE_ to _TEN_ cache lines into the processor just to lookup _ONE_ page.
Franks a lot, David S. Miller davem@redhat.com
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