Re: [PATCH] PPC64 iSeries: cleanup viopath

From: Linas Vepstas
Date: Tue Mar 15 2005 - 12:54:09 EST

On Wed, Mar 16, 2005 at 02:53:39AM +1100, Stephen Rothwell was heard to remark:
> On Tue, 15 Mar 2005 08:32:27 -0600 Hollis Blanchard <hollis@xxxxxxxxxxxxxx> wrote:
> >
> > Why not use a byte instead of a full int (reordering the members for
> > alignment)?
> Because "classical" boleans are ints.
> Because I don't know the relative speed of accessing single byte variables.
> Because it was easy.
> Because we only allocate 32 of these structures. Changing them really
> only adds four bytes per structure. I guess using bytes and rearranging
> the structure could actually save 4 bytes per structure.

FWIW, keep in mind that a cache miss due to large structures not fitting
is a zillion times more expensive than byte-aligning in the cpu
(even if byte operands had a cpu perf overhead, which I don't think
they do on ppc).

> It really makes little difference,

Yep. So my apologies for making you read this email.


To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at