From: Mark Kettenis <mark.kettenis@xs4all.nl>
Subject: Re: fail earlier in pgo_get
To: Martin Pieuchot <mpi@grenadille.net>
Cc: tech@openbsd.org
Date: Sat, 08 Nov 2025 22:46:47 +0100

> Date: Sat, 8 Nov 2025 17:23:34 +0000
> From: Martin Pieuchot <mpi@grenadille.net>
> 
> On 27/10/25(Mon) 10:34, Martin Pieuchot wrote:
> > Stop iterating as soon as a page is missing or busy when all pages are
> > asked by the caller.
> > 
> > Note that currently pgo_get() is not called with PGO_ALLPAGES in the
> > kernel.

That isn't true; see uvm_obj_wire().

This change would be fine for that case though and could indeed speed
things up a bit.

> > This is a requirement for upcoming changes.

Can you elaborate on that?  Do those upcoming changes add additional
pgo_get() calls?

> > 
> > ok?
> 
> Anyone?
> 
> > Index: uvm/uvm_aobj.c
> > ===================================================================
> > RCS file: /cvs/src/sys/uvm/uvm_aobj.c,v
> > diff -u -p -r1.116 uvm_aobj.c
> > --- uvm/uvm_aobj.c	10 Mar 2025 14:13:58 -0000	1.116
> > +++ uvm/uvm_aobj.c	27 Oct 2025 09:31:40 -0000
> > @@ -1024,10 +1024,13 @@ uao_get(struct uvm_object *uobj, voff_t 
> >  			 * to be useful must get a non-busy page
> >  			 */
> >  			if (ptmp == NULL || (ptmp->pg_flags & PG_BUSY) != 0) {
> > -				if (lcv == centeridx ||
> > -				    (flags & PGO_ALLPAGES) != 0)
> > +				if (lcv == centeridx)
> >  					/* need to do a wait or I/O! */
> >  					done = FALSE;

I think adding a set of curly braces here would make sense.

> > +				if ((flags & PGO_ALLPAGES) != 0) {
> > +					done = FALSE;
> > +					break;
> > +				}
> >  				continue;
> >  			}
> >  
> > Index: uvm/uvm_vnode.c
> > ===================================================================
> > RCS file: /cvs/src/sys/uvm/uvm_vnode.c,v
> > diff -u -p -r1.142 uvm_vnode.c
> > --- uvm/uvm_vnode.c	29 Sep 2025 09:55:01 -0000	1.142
> > +++ uvm/uvm_vnode.c	27 Oct 2025 09:32:09 -0000
> > @@ -977,10 +990,13 @@ uvn_get(struct uvm_object *uobj, voff_t 
> >  			 * to be useful must get a non-busy page
> >  			 */
> >  			if (ptmp == NULL || (ptmp->pg_flags & PG_BUSY) != 0) {
> > -				if (lcv == centeridx ||
> > -				    (flags & PGO_ALLPAGES) != 0)
> > +				if (lcv == centeridx)
> >  					/* need to do a wait or I/O! */
> >  					done = FALSE;

Same here.

> > +				if ((flags & PGO_ALLPAGES) != 0) {
> > +					done = FALSE;
> > +					break;
> > +				}
> >  				continue;
> >  			}
> >  
> > 
> > 
> 
> 
>