Re: [PATCH] ppc32 copy_to_user dcbt fixup

From: Benjamin Herrenschmidt
Date: Sat Mar 13 2004 - 03:44:28 EST

On Sat, 2004-03-13 at 18:49, Bryan Rittmeyer wrote:
> On Sat, Mar 13, 2004 at 03:50:03PM +1100, Benjamin Herrenschmidt wrote:
> > It would be wise to make the dcbz as long as possible in "advance"
> > before the actual write to the cache line.
> I guess we could try "pre-dcbz" ala the dcbt prefetch code.
> Even dcbz right before stw is probably cheaper than RAM
> loading data that will be totally overwritten. It's hard to
> lose eliminating bus I/O (especially reads).

Except if the target is already in the cache... difficult choice.

> Any comments on the dcbt prefetch patch?

Didn't have time to look at it in details yet, maybe not before
monday or tuesday


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