On Thu, Aug 24, 2006 at 08:38:38PM +0900, Atsushi Nemoto wrote:
> Date: Thu, 24 Aug 2006 20:38:38 +0900 (JST)
> To: firstname.lastname@example.org
> Cc: email@example.com, firstname.lastname@example.org
> Subject: Re: [PATCH] fix cache coherency issues
> From: Atsushi Nemoto <email@example.com>
> Content-Type: Text/Plain; charset=us-ascii
> On Thu, 24 Aug 2006 12:15:15 +0100, Ralf Baechle <firstname.lastname@example.org> wrote:
> > Your patch also still contains copy_user_page(). The only user of it used
> > to be copy_user_highpage() so after our rewrite it can go away. I've
> > already applied both fixes to my working version of the patch.
> Yes, it is intentional. I keep copy_user_page() just because it is
> described in cachetlb.txt and exported.
> Of course we can remove it. I do not care :-) Also I wondered we
> should export copy_user_highpage() or not ...
> > Your patch only maps the source page. I'm trying to map the destination
> > page also and I'm hitting a few issues with it.
> If you wanted to map the destination, you must writeback the dcache
> via kernel mapping first. The dcache can contain dirty data for the
> page by previous usage. And if the page was executable, we must flush
> the destination page after copy_page() (via coherent mapping) anyway
> for I/D coherency.
> So now I think mapping the destination is not worth to do.
I figured it was worth a try. It means the process will start running with
a hot copy of the COW page instead of a cold copy and I can use hit
invalidates instead of hit wbinv on the kernel address of the to page.
Lmbenching now, stay tuned ...