On Sun, Nov 13, 2011 at 01:37:43AM +0900, Minchan Kim wrote:

I saw the following accouting of compaction during test of the series.

compact_blocks_moved 251
compact_pages_moved 44

It's very awkward to me although it's possbile because it means we try to compact 251 blocks
but it just migrated 44 pages. As further investigation, I found isolate_migratepages doesn't
isolate any pages but it returns ISOLATE_SUCCESS and then, it just increases compact_blocks_moved
but doesn't increased compact_pages_moved.

This patch makes accouting of compaction works only in case of success of isolation.

CC: Mel Gorman <mgorman@suse.de>
CC: Johannes Weiner <redacted>
CC: Rik van Riel <redacted>
Signed-off-by: Minchan Kim <redacted>

Acked-by: Johannes Weiner <redacted>

It's a teensy-bit awkward that isolate_migratepages() can return
success without actually isolating any new pages, just because there
are still some pages left from a previous run (cc->nr_migratepages is
maintained across isolation calls).

Maybe isolate_migratepages() should just return an error if compaction
should really be aborted and 0 otherwise, and have compact_zone()
always check for cc->nr_migratepages itself?

	if (isolate_migratepages(zone, cc) < 0) {
		ret = COMPACT_PARTIAL;
		goto out;
	}

	if (!cc->nr_migratepages)
		continue;

	...

Just a nit-pick, though.  If you don't agree, just leave it as is.

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