From: Theo Buehler <tb@openbsd.org>
Subject: Re: uvm_fault_upper_lookup: delay pmap_extract()
To: tech@openbsd.org
Date: Thu, 28 Nov 2024 10:35:10 +0100

On Thu, Nov 28, 2024 at 10:01:15AM +0100, Martin Pieuchot wrote:
> uvm_fault_upper_lookup() enters existing neighbor pages found in the
> amap.
> 
> Diff below reorder the checks in the loop to avoid calling the expensive
> pmap_extract(9) when there is no corresponding anon or if the page is
> PG_RELEASED|PG_BUSY and won't be entered anyway.
> 
> While here call pmap_update() only if, at least, a page has been entered.

As far as I can see pmap_update() is always a noop. Is this expected to
change?

ok tb