Re: [PATCH 0/4] Tune and tweak memmove/wordcopy code for Powerpc

[David Miller <davem at davemloft dot net>]

From: Will Schmidt <will_schmidt@vnet.ibm.com>
Date: Mon, 19 Mar 2012 16:01:30 -0500

> The "Call memcpy when appropriate" optimization (4/4) could apply to
> other architectures generically; but I can not make any claims to
> how much improvement (if any) it provides for those archs.

One problem with this is that currently internal calls to memcpy
inside of libc won't use the IFUNC variant.

Right now __GI_memcpy ends up being set to the least-optimized variant
a sysdep provides.  The same thing happens for memset.

This is done primarily because it's hard to ensure that we won't make
a memcpy or memset call before the dynamic linker is done booting up
and this is able to run the PLT resolver properly.  I really think
we can and should fix this though.

I've seen the unoptimized memset and memcpy show up in the profiles
under certain workloads, so it's not just a "would be nice" kind of
issue.

On another note, do you guys plan on converting all of this chip
specific powerpc code over to multiarch so you can share those
problems with the rest of us?  :-)