On Wed 03-05-17 08:15:28, Michal Hocko wrote:
> On Tue 02-05-17 13:41:23, David Rientjes wrote:
> > On Tue, 2 May 2017, Michal Hocko wrote:
[...]
> > > I do agree that blindly
> > > scanning anon pages when file pages are low is very suboptimal but this
> > > adds yet another heuristic without _any_ numbers. Why cannot we simply
> > > treat anon and file pages equally? Something like the following
> > >
> > > if (pgdatfile + pgdatanon + pgdatfree > 2*total_high_wmark) {
> > > scan_balance = SCAN_FILE;
> > > if (pgdatfile < pgdatanon)
> > > scan_balance = SCAN_ANON;
> > > goto out;
> > > }
> > >
> >
> > This would be substantially worse than the current code because it
> > thrashes the anon lru when anon out numbers file pages rather than at the
> > point we fall under the high watermarks for all eligible zones. If you
> > tested your suggestion, you could see gigabytes of memory left untouched
> > on the file lru. Anonymous memory is more probable to be part of the
> > working set.
>
> This was supposed to be more an example of a direction I was thinking,
> definitely not a final patch. I will think more to come up with a
> more complete proposal.
This is still untested but should be much closer to what I've had in
mind.
---
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 24efcc20af91..bcdad30f942d 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2174,8 +2174,14 @@ static void get_scan_count(struct lruvec *lruvec, struct mem_cgroup *memcg,
}
if (unlikely(pgdatfile + pgdatfree <= total_high_wmark)) {
- scan_balance = SCAN_ANON;
- goto out;
+ unsigned long pgdatanon;
+
+ pgdatanon = node_page_state(pgdat, NR_ACTIVE_ANON) +
+ node_page_state(pgdat, NR_INACTIVE_ANON);
+ if (pgdatanon + pgdatfree > total_high_wmark) {
+ scan_balance = SCAN_ANON;
+ goto out;
+ }
}
}
--
Michal Hocko
SUSE Labs
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