Subject: Re: AltiVec in the kernel

From: [email-masked] (Linas Vepstas)
Date: Thu, 20 Jul 2006 12:42:55 -0500

On Thu, Jul 20, 2006 at 07:31:32AM -0500, Matt Sealey wrote:
> 
> What's the case in the kernel for the memcpy functions etc., are
> they optimized for doing things like longword copies rather than
> byte-per-byte etc.? 

arch/powerpc/lib/copy_32.S
arch/powerpc/lib/memcpy_64.S

Looks pretty darned optimized to me.

> We found glibc sucked for that.

Only because someone was asleep at the wheel, or there was a bug. 

When glibc gets ported to a new architecture, one of the earliest 
tasks is to create optimized versions of memcpy and the like. 
Presumably, on powerpc, this would have been done more than a 
decade ago; its hard for me to imagine that there'd be a problem 
there.  Now, I haven't looked at the code, but I just can't imagine 
how this would not have been found and fixed by now. Is there
really a problem wiht glibc performance on powerpc? I mean,
this is a pretty serious accusation, and something that should 
be fixed asap.

--linas