On Wed 03-05-17 15:52:04, David Rientjes wrote:
> On Wed, 3 May 2017, Michal Hocko wrote:
[...]
> > /*
> > - * If there is enough inactive page cache, i.e. if the size of the
> > - * inactive list is greater than that of the active list *and* the
> > - * inactive list actually has some pages to scan on this priority, we
> > - * do not reclaim anything from the anonymous working set right now.
> > - * Without the second condition we could end up never scanning an
> > - * lruvec even if it has plenty of old anonymous pages unless the
> > - * system is under heavy pressure.
> > + * Make sure there are enough pages on the biased LRU before we go
> > + * and do an exclusive reclaim from that list, i.e. if the
> > + * size of the inactive list is greater than that of the active list
> > + * *and* the inactive list actually has some pages to scan on this
> > + * priority.
> > + * Without the second condition we could end up never scanning other
> > + * lruvecs even if they have plenty of old pages unless the system is
> > + * under heavy pressure.
> > */
> > - if (!inactive_list_is_low(lruvec, true, memcg, sc, false) &&
> > - lruvec_lru_size(lruvec, LRU_INACTIVE_FILE, sc->reclaim_idx) >> sc->priority) {
> > - scan_balance = SCAN_FILE;
> > + lru = LRU_INACTIVE_ANON + LRU_FILE * (scan_balance == SCAN_FILE);
>
> This part seems to complicate the logic since it determines the lru under
> test based on the current setting of scan_balance. I think I prefer
> individual heuristics with well written comments, but others may feel
> differently about this.
I do not claim the code would more obvious than before but it gets rid
of the duplication which is usually a good thing. This size check has
the same reasoning regardless of the type of the LRU. But I am not going
to insist...
> > + if (!inactive_list_is_low(lruvec, is_file_lru(lru), memcg, sc, false) &&
> > + lruvec_lru_size(lruvec, lru, sc->reclaim_idx) >> sc->priority)
> > goto out;
> > - }
> >
> > scan_balance = SCAN_FRACT;
> >
--
Michal Hocko
SUSE Labs
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