Re: [patches] Possible PowerPC LIBC optimization

[Steven Munroe <munroesj@xxxxxxxxxx>]

Mark Hatle wrote:
> In the PowerPC community Conn Clark has been doing some interesting
> optimization work in glibc.  Much of it however, doesn't seem to be
> acceptable to the mainline glibc due to being very processor and
> architecture specific.
>
> The following information describes a simple change that made a large
> performance improvement on the PPC 750 processor, and is believed will
> make similar improvements on other PowerPC that contain the dcbt
> instruction.
>   
Hi, these kind of change may be more appropriate for the powerpc-cpu
add-on then the core libc tree. I have discussed this
<http://www.penguinppc64.org/dev/glibc/glibc-powerpc-cpu-addon.html> in
the past with Conn.

My concern is that what works for 750 may not be best for 8540 or 970.
The powerpc-cpu add-on handles this by adding additional <cpu-type>
specific directory layer to the make system search order (i.e.
./sysdeps/powerpc/powerpc32/750) that can override the base. This is
selected at configure time via --with-cpu=750 or your favorite <cpu-type>

I can contribute this to eglibc as an add-on (like ports) or we can
discuss integrating this into the libc tree.