On Mon, Aug 03, 2015 at 11:55:46PM +0900, Jaewon Kim wrote:
>
>
> On 2015년 08월 03일 21:27, Minchan Kim wrote:
> > Hello,
> >
> > On Mon, Aug 03, 2015 at 07:18:27PM +0900, Jaewon Kim wrote:
> >> reclaim_clean_pages_from_list() decreases NR_ISOLATED_FILE by returned
> >> value from shrink_page_list(). But mlocked pages in the isolated
> >> clean_pages page list would be removed from the list but not counted as
> >> nr_reclaimed. Fix this miscounting by returning the number of mlocked
> >> pages and count it.
> >
> > If there are pages not able to reclaim, VM try to migrate it and
> > have to handle the stat in migrate_pages.
> > If migrate_pages fails again, putback-fiends should handle it.
> >
> > Is there anyting I am missing now?
> >
> > Thanks.
> >
> Hello
>
> Only pages in cc->migratepages will be handled by migrate_pages or
> putback_movable_pages, and NR_ISOLATED_FILE will be counted properly.
> However mlocked pages will not be put back into cc->migratepages,
> and also not be counted in NR_ISOLATED_FILE because putback_lru_page
> in shrink_page_list does not increase NR_ISOLATED_FILE.
> The current reclaim_clean_pages_from_list assumes that shrink_page_list
> returns number of pages removed from the candidate list.
>
> i.e)
> isolate_migratepages_range : NR_ISOLATED_FILE += 10
> reclaim_clean_pages_from_list : NR_ISOLATED_FILE -= 5 (1 mlocked page)
> migrate_pages : NR_ISOLATED_FILE -=4
> => NR_ISOLATED_FILE increased by 1
Thanks for the clarity.
I think the problem is shrink_page_list is awkard. It put back to
unevictable pages instantly instead of passing it to caller while
it relies on caller for non-reclaimed-non-unevictable page's putback.
I think we can make it consistent so that shrink_page_list could
return non-reclaimed pages via page_list and caller can handle it.
As a bonus, it could try to migrate mlocked pages without retrial.
>
> Thank you.
> >>
> >> Signed-off-by: Jaewon Kim <jaewon31.kim@xxxxxxxxxxx>
> >> ---
> >> mm/vmscan.c | 10 ++++++++--
> >> 1 file changed, 8 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/mm/vmscan.c b/mm/vmscan.c
> >> index 5e8eadd..5837695 100644
> >> --- a/mm/vmscan.c
> >> +++ b/mm/vmscan.c
> >> @@ -849,6 +849,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
> >> unsigned long *ret_nr_congested,
> >> unsigned long *ret_nr_writeback,
> >> unsigned long *ret_nr_immediate,
> >> + unsigned long *ret_nr_mlocked,
> >> bool force_reclaim)
> >> {
> >> LIST_HEAD(ret_pages);
> >> @@ -1158,6 +1159,7 @@ cull_mlocked:
> >> try_to_free_swap(page);
> >> unlock_page(page);
> >> putback_lru_page(page);
> >> + (*ret_nr_mlocked)++;
> >> continue;
> >>
> >> activate_locked:
> >> @@ -1197,6 +1199,7 @@ unsigned long reclaim_clean_pages_from_list(struct zone *zone,
> >> .may_unmap = 1,
> >> };
> >> unsigned long ret, dummy1, dummy2, dummy3, dummy4, dummy5;
> >> + unsigned long nr_mlocked = 0;
> >> struct page *page, *next;
> >> LIST_HEAD(clean_pages);
> >>
> >> @@ -1210,8 +1213,10 @@ unsigned long reclaim_clean_pages_from_list(struct zone *zone,
> >>
> >> ret = shrink_page_list(&clean_pages, zone, &sc,
> >> TTU_UNMAP|TTU_IGNORE_ACCESS,
> >> - &dummy1, &dummy2, &dummy3, &dummy4, &dummy5, true);
> >> + &dummy1, &dummy2, &dummy3, &dummy4, &dummy5,
> >> + &nr_mlocked, true);
> >> list_splice(&clean_pages, page_list);
> >> + ret += nr_mlocked;
> >> mod_zone_page_state(zone, NR_ISOLATED_FILE, -ret);
> >> return ret;
> >> }
> >> @@ -1523,6 +1528,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
> >> unsigned long nr_unqueued_dirty = 0;
> >> unsigned long nr_writeback = 0;
> >> unsigned long nr_immediate = 0;
> >> + unsigned long nr_mlocked = 0;
> >> isolate_mode_t isolate_mode = 0;
> >> int file = is_file_lru(lru);
> >> struct zone *zone = lruvec_zone(lruvec);
> >> @@ -1565,7 +1571,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
> >>
> >> nr_reclaimed = shrink_page_list(&page_list, zone, sc, TTU_UNMAP,
> >> &nr_dirty, &nr_unqueued_dirty, &nr_congested,
> >> - &nr_writeback, &nr_immediate,
> >> + &nr_writeback, &nr_immediate, &nr_mlocked,
> >> false);
> >>
> >> spin_lock_irq(&zone->lru_lock);
> >> --
> >> 1.9.1
> >>
> >
--
Kind regards,
Minchan Kim
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