On Mon 01-05-17 14:34:21, David Rientjes wrote:
[...]
> @@ -2204,8 +2204,17 @@ 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;
> + /*
> + * Force SCAN_ANON if there are enough inactive
> + * anonymous pages on the LRU in eligible zones.
> + * Otherwise, the small LRU gets thrashed.
> + */
> + if (!inactive_list_is_low(lruvec, false, sc, false) &&
> + lruvec_lru_size(lruvec, LRU_INACTIVE_ANON, sc->reclaim_idx)
> + >> sc->priority) {
> + scan_balance = SCAN_ANON;
> + goto out;
> + }
I have already asked and my questions were ignored. So let me ask again
and hopefuly not get ignored this time. So Why do we need a different
criterion on anon pages than file pages? 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;
}
Also it would help to describe the workload which can trigger this
behavior so that we can compare numbers before and after this patch.
--
Michal Hocko
SUSE Labs
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