On Wed, Jul 06, 2016 at 09:31:21AM +0100, Mel Gorman wrote:
> On Wed, Jul 06, 2016 at 09:30:54AM +0900, Minchan Kim wrote:
> > On Tue, Jul 05, 2016 at 11:26:39AM +0100, Mel Gorman wrote:
> >
> > <snip>
> >
> > > > > @@ -3418,10 +3426,10 @@ void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
> > > > > if (!cpuset_zone_allowed(zone, GFP_KERNEL | __GFP_HARDWALL))
> > > > > return;
> > > > > pgdat = zone->zone_pgdat;
> > > > > - if (pgdat->kswapd_max_order < order) {
> > > > > - pgdat->kswapd_max_order = order;
> > > > > - pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx);
> > > > > - }
> > > > > + if (pgdat->kswapd_classzone_idx == -1)
> > > > > + pgdat->kswapd_classzone_idx = classzone_idx;
> > > >
> > > > It's tricky. Couldn't we change kswapd_classzone_idx to integer type
> > > > and remove if above if condition?
> > > >
> > >
> > > It's tricky and not necessarily better overall. It's perfectly possible
> > > to be woken up for zone index 0 so it's changing -1 to another magic
> > > value.
> >
> > I don't get it. What is a problem with this?
> >
>
> It becomes difficult to tell the difference between "no wakeup and init to
> zone 0" and "wakeup and reclaim for zone 0". At least that's the problem
> I ran into when I tried before settling on -1.
Sorry for bothering you several times. I cannot parse what you mean.
I didn't mean -1 is problem here but why do we need below two lines
I removed?
IOW, what's the problem if we apply below patch?
diff --git a/mm/vmscan.c b/mm/vmscan.c
index c538a8c..6eb23f5 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3413,9 +3413,7 @@ void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
if (!cpuset_zone_allowed(zone, GFP_KERNEL | __GFP_HARDWALL))
return;
pgdat = zone->zone_pgdat;
- if (pgdat->kswapd_classzone_idx == -1)
- pgdat->kswapd_classzone_idx = classzone_idx;
- pgdat->kswapd_classzone_idx = max(pgdat->kswapd_classzone_idx, classzone_idx);
+ pgdat->kswapd_classzone_idx = max_t(int, pgdat->kswapd_classzone_idx, classzone_idx);
pgdat->kswapd_order = max(pgdat->kswapd_order, order);
if (!waitqueue_active(&pgdat->kswapd_wait))
return;
>
> --
> Mel Gorman
> SUSE Labs
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