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mm, vmscan: account for skipped pages as a partial scan 

Page reclaim determines whether a pgdat is unreclaimable by examining
how many pages have been scanned since a page was freed and comparing
that to the LRU sizes.  Skipped pages are not reclaim candidates but
contribute to scanned.  This can prematurely mark a pgdat as
unreclaimable and trigger an OOM kill.

This patch accounts for skipped pages as a partial scan so that an
unreclaimable pgdat will still be marked as such but by scaling the cost
of a skip, it'll avoid the pgdat being marked prematurely.

Link: http://lkml.kernel.org/r/1469110261-7365-6-git-send-email-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
hifive-unleashed-5.1
Mel Gorman 2016-07-28 15:47:37 -07:00 committed by Linus Torvalds
parent f8d1a31163
commit d7f05528ee
1 changed files with 18 additions and 2 deletions
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20
mm/vmscan.c
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@ -1424,7 +1424,7 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
LIST_HEAD(pages_skipped);
for (scan = 0; scan < nr_to_scan && nr_taken < nr_to_scan &&
!list_empty(src); scan++) {
!list_empty(src);) {
struct page *page;
page = lru_to_page(src);
@ -1438,6 +1438,12 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
continue;
}
/*
* Account for scanned and skipped separetly to avoid the pgdat
* being prematurely marked unreclaimable by pgdat_reclaimable.
*/
scan++;
switch (__isolate_lru_page(page, mode)) {
case 0:
nr_pages = hpage_nr_pages(page);
@ -1465,14 +1471,24 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
*/
if (!list_empty(&pages_skipped)) {
int zid;
unsigned long total_skipped = 0;
list_splice(&pages_skipped, src);
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];
}
/*
* Account skipped pages as a partial scan as the pgdat may be
* 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;
list_splice(&pages_skipped, src);
}
*nr_scanned = scan;
trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, nr_to_scan, scan,