Re: [PATCH] 2.5.14 IDE 56

Andi Kleen (ak@muc.de)
10 May 2002 02:33:19 +0200


Andrew Morton <akpm@zip.com.au> writes:

> For bulk read() and write() I/O the best sized buffer is 8 kbytes. 4k is
> pretty good, too. Anything larger blows the user-side buffer out of L1.
> This is for x86.

Modern x86 support prefetch hints for the CPU to tell it to not
pollute the caches with "streaming data". I bet using them would
be a big win. The rep ; movsl loop used in copy*user isn't
very good on modern x86 anyways (it is ok on PPro, but loses on Athlon
and P4)

I'm (slowly) working on such functions for x86-64, it should be eventually
possible to backport them to i386.

-Andi
-
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/