Messages in this thread | | | From | "Huang\, Ying" <> | Subject | Re: [PATCH] mm: vmscan: correct nr_reclaimed for THP | Date | Fri, 10 May 2019 10:12:40 +0800 |
| |
Yang Shi <yang.shi@linux.alibaba.com> writes:
> Since commit bd4c82c22c36 ("mm, THP, swap: delay splitting THP after > swapped out"), THP can be swapped out in a whole. But, nr_reclaimed > still gets inc'ed by one even though a whole THP (512 pages) gets > swapped out. > > This doesn't make too much sense to memory reclaim. For example, direct > reclaim may just need reclaim SWAP_CLUSTER_MAX pages, reclaiming one THP > could fulfill it. But, if nr_reclaimed is not increased correctly, > direct reclaim may just waste time to reclaim more pages, > SWAP_CLUSTER_MAX * 512 pages in worst case. > > This change may result in more reclaimed pages than scanned pages showed > by /proc/vmstat since scanning one head page would reclaim 512 base pages. > > Cc: "Huang, Ying" <ying.huang@intel.com> > Cc: Johannes Weiner <hannes@cmpxchg.org> > Cc: Michal Hocko <mhocko@suse.com> > Cc: Mel Gorman <mgorman@techsingularity.net> > Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com> > Cc: Hugh Dickins <hughd@google.com> > Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com> > --- > I'm not quite sure if it was the intended behavior or just omission. I tried > to dig into the review history, but didn't find any clue. I may miss some > discussion. > > mm/vmscan.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index fd9de50..7e026ec 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -1446,7 +1446,11 @@ static unsigned long shrink_page_list(struct list_head *page_list, > > unlock_page(page); > free_it: > - nr_reclaimed++; > + /* > + * THP may get swapped out in a whole, need account > + * all base pages. > + */ > + nr_reclaimed += (1 << compound_order(page)); > > /* > * Is there need to periodically free_page_list? It would
Good catch! Thanks!
How about to change this to
nr_reclaimed += hpage_nr_pages(page);
Best Regards, Huang, Ying
| |