Re: [PATCH -mm] swsusp: rework memory shrinker

["Rafael J. Wysocki" <rjw@sisk.pl>]

On Tuesday 18 April 2006 12:13, Andrew Morton wrote:
> "Rafael J. Wysocki" <rjw@sisk.pl> wrote:
> >
> > Rework the swsusp's memory shrinker in the following way:
> 
> And what was the observed effect of all this?

Measurable effects:
1) It tends to free only as much memory as required, eg. if the image_size
is set to 450 MB, the actual image sizes are almost always well above
400 MB and they tended to be below that number without the patch
(~5-10% of a difference, but still :-)).
2) If image_size = 0, it frees everything that can be freed without any
workarounds (we had to add the additional loop checking for
ret >= nr_pages with the additional blk_congestion_wait() to the
"original" shrinker to achieve this).

A non-measurable effect is that with the patch applied  the system seems to
be more responsive after resume, but of course this may be an illusion.

> 
> > +		/* Force reclaiming mapped pages in the passes #3 and #4 */
> > +		if (pass > 2) {
> > +			sc.may_swap = 1;
> > +			vm_swappiness = 100;
> > +		}
> 
> That's a bit klunky.   Maybe we should move swappiness into scan_control.

Alternatively we can temporarily set zone->prev_priority to 100 in
shrink_all_zones() if pass > 2?