Subject: Re: optimizations [for non-debugging] amd64 kernels
To: Blair Sadewitz <email@example.com>
From: Andrew Doran <firstname.lastname@example.org>
Date: 09/11/2007 12:25:49
On Tue, Sep 11, 2007 at 07:09:31AM -0400, Blair Sadewitz wrote:
> Also, at:
> is an enhancement for x86_64 memcpy/bzero/bcopy functions in
> common/libc. This is authored by email@example.com and is a slight
> modification of the latest version (<see
> http://www.hadaly.org/fuyuki>) of what was originally posted in a PR
> back around Jan/Feb.
> I'd appreciate it if someone who actually knew x86_64 assembly would
> take a look at this and/or if others would test it so we could get it
> in the tree at some point.
The setup and teardown for stos/movs/cmps are really expensive and for small
strings (like under 512 bytes) you're better off with really simple loops
using the arithemetic instructions.