mm, vmscan: account for skipped pages as a partial scan (d7f05528) · Commits · 戴 / test

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>

mm/vmscan.c

+18 −2

Original line number	Diff line number	Diff line
		@@ -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,

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