lkml.org 
[lkml]   [2001]   [Nov]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: speed difference between using hard-linked and modular drives?
From
   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

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:13    [W:0.113 / U:2.580 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site