mm: avoid calling pgdat_balanced() needlessly (dafcb73e) · Commits · 戴 / test

Now that balance_pgdat() is slightly tidied up, thanks to more capable pgdat_balanced(), it's become obvious that pgdat_balanced() is called to check the status, then break the loop if pgdat is balanced, just to be immediately called again. The second call is completely unnecessary, of course. The patch introduces pgdat_is_balanced boolean, which helps resolve the above suboptimal behavior, with the added benefit of slightly better documenting one other place in the function where we jump and skip lots of code. Signed-off-by:

Zlatko Calusic <zlatko.calusic@iskon.hr> Cc: Mel Gorman <mgorman@suse.de> Cc: Hugh Dickins <hughd@google.com> Cc: Minchan Kim <minchan.kim@gmail.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

mm/vmscan.c

+11 −4

Original line number	Diff line number	Diff line
		@@ -2616,6 +2616,7 @@ static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order, long remaining,
		static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
		int *classzone_idx)
		{
		bool pgdat_is_balanced = false;
		struct zone *unbalanced_zone;
		int i;
		int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
		@@ -2690,8 +2691,11 @@ loop_again:
		zone_clear_flag(zone, ZONE_CONGESTED);
		}
		}
		if (i < 0)

		if (i < 0) {
		pgdat_is_balanced = true;
		goto out;
		}

		for (i = 0; i <= end_zone; i++) {
		struct zone *zone = pgdat->node_zones + i;
		@@ -2818,8 +2822,11 @@ loop_again:
		pfmemalloc_watermark_ok(pgdat))
		wake_up(&pgdat->pfmemalloc_wait);

		if (pgdat_balanced(pgdat, order, *classzone_idx))
		if (pgdat_balanced(pgdat, order, *classzone_idx)) {
		pgdat_is_balanced = true;
		break; /* kswapd: all done */
		}

		/*
		* OK, kswapd is getting into trouble. Take a nap, then take
		* another pass across the zones.
		@@ -2840,9 +2847,9 @@ loop_again:
		if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
		break;
		} while (--sc.priority >= 0);
		out:

		if (!pgdat_balanced(pgdat, order, *classzone_idx)) {
		out:
		if (!pgdat_is_balanced) {
		cond_resched();

		try_to_freeze();

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