On Tue 03-01-17 18:21:48, Vlastimil Babka wrote:
> On 12/28/2016 04:30 PM, Michal Hocko wrote:
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -1428,6 +1428,7 @@ static unsigned long isolate_lru_pages(unsigned long
> > nr_to_scan,
> > unsigned long nr_taken = 0;
> > unsigned long nr_zone_taken[MAX_NR_ZONES] = { 0 };
> > unsigned long nr_skipped[MAX_NR_ZONES] = { 0, };
> > + unsigned long skipped = 0, total_skipped = 0;
> > unsigned long scan, nr_pages;
> > LIST_HEAD(pages_skipped);
> >
> > @@ -1479,14 +1480,13 @@ static unsigned long isolate_lru_pages(unsigned
> > long nr_to_scan,
> > */
> > if (!list_empty(&pages_skipped)) {
> > int zid;
> > - unsigned long total_skipped = 0;
> >
> > for (zid = 0; zid < MAX_NR_ZONES; zid++) {
> > if (!nr_skipped[zid])
> > continue;
> >
> > __count_zid_vm_events(PGSCAN_SKIP, zid,
> > nr_skipped[zid]);
> > - total_skipped += nr_skipped[zid];
> > + skipped += nr_skipped[zid];
> > }
> >
> > /*
> > @@ -1494,13 +1494,13 @@ static unsigned long isolate_lru_pages(unsigned
> > long nr_to_scan,
> > * close to unreclaimable. If the LRU list is empty, account
> > * skipped pages as a full scan.
> > */
> > - scan += list_empty(src) ? total_skipped : total_skipped >> 2;
> > + total_skipped = list_empty(src) ? skipped : skipped >> 2;
>
> Should the tracepoint output reflect this halving heuristic or rather report
> the raw data? Or is each variant inferrable from the other?
I would rather see the raw data because you can always go and check the
_current_ implementation and calculate the heuristic.
--
Michal Hocko
SUSE Labs
