Re: [patch 1/2] mm, compaction: kcompactd should not ignore pageblock skip
From: Vlastimil Babka <hidden>
Date: 2017-08-23 08:24:09
Also in:
linux-mm
On 08/16/2017 01:39 AM, David Rientjes wrote:
Kcompactd is needlessly ignoring pageblock skip information. It is doing MIGRATE_SYNC_LIGHT compaction, which is no more powerful than MIGRATE_SYNC compaction. If compaction recently failed to isolate memory from a set of pageblocks, there is nothing to indicate that kcompactd will be able to do so, or that it is beneficial from attempting to isolate memory. Use the pageblock skip hint to avoid rescanning pageblocks needlessly until that information is reset. Signed-off-by: David Rientjes <rientjes@google.com>
It would be much better if patches like this were accompanied by some numbers. Also there's now a danger that in cases where there's no direct compaction happening (just kcompactd), nothing will ever call __reset_isolation_suitable().
quoted hunk ↗ jump to hunk
--- mm/compaction.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)diff --git a/mm/compaction.c b/mm/compaction.c --- a/mm/compaction.c +++ b/mm/compaction.c@@ -1927,9 +1927,8 @@ static void kcompactd_do_work(pg_data_t *pgdat) .total_free_scanned = 0, .classzone_idx = pgdat->kcompactd_classzone_idx, .mode = MIGRATE_SYNC_LIGHT, - .ignore_skip_hint = true, + .ignore_skip_hint = false, .gfp_mask = GFP_KERNEL, - }; trace_mm_compaction_kcompactd_wake(pgdat->node_id, cc.order, cc.classzone_idx);