>> + if (zone_watermark_ok(zone, cc.order, low_wmark_pages(zone),
>> + cc.classzone_idx, 0)) {
>> + success = true;
>> + compaction_defer_reset(zone, cc.order, false);
>> + } else if (cc.mode != MIGRATE_ASYNC &&
>> + status == COMPACT_COMPLETE) {
>> + defer_compaction(zone, cc.order);
>> + }
>
> We alerady set mode to MIGRATE_SYNC_LIGHT so this cc.mode check looks weird.
> It would be better to change it and add some comment that we can
> safely call defer_compaction() here.
Right.
>> +
>> + VM_BUG_ON(!list_empty(&cc.freepages));
>> + VM_BUG_ON(!list_empty(&cc.migratepages));
>> + }
>> +
>> + /*
>> + * Regardless of success, we are done until woken up next. But remember
>> + * the requested order/classzone_idx in case it was higher/tighter than
>> + * our current ones
>> + */
>> + if (pgdat->kcompactd_max_order <= cc.order)
>> + pgdat->kcompactd_max_order = 0;
>> + if (pgdat->classzone_idx >= cc.classzone_idx)
>> + pgdat->classzone_idx = pgdat->nr_zones - 1;
>> +}
>
> Maybe, you intend to update kcompactd_classzone_idx.
Oops, true. Thanks for the review!
Here's a fixlet.
----8<----
From: Vlastimil Babka <vbabka@xxxxxxx>
Date: Wed, 2 Mar 2016 10:15:22 +0100
Subject: mm-compaction-introduce-kcompactd-fix-3
Remove extraneous check for sync compaction before deferring.
Correctly adjust kcompactd's classzone_idx instead of kswapd's.
Reported-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
---
mm/compaction.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/mm/compaction.c b/mm/compaction.c
index c03715ba65c7..9a605c3d4177 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1811,8 +1811,11 @@ static void kcompactd_do_work(pg_data_t *pgdat)
cc.classzone_idx, 0)) {
success = true;
compaction_defer_reset(zone, cc.order, false);
- } else if (cc.mode != MIGRATE_ASYNC &&
- status == COMPACT_COMPLETE) {
+ } else if (status == COMPACT_COMPLETE) {
+ /*
+ * We use sync migration mode here, so we defer like
+ * sync direct compaction does.
+ */
defer_compaction(zone, cc.order);
}
@@ -1827,8 +1830,8 @@ static void kcompactd_do_work(pg_data_t *pgdat)
*/
if (pgdat->kcompactd_max_order <= cc.order)
pgdat->kcompactd_max_order = 0;
- if (pgdat->classzone_idx >= cc.classzone_idx)
- pgdat->classzone_idx = pgdat->nr_zones - 1;
+ if (pgdat->kcompactd_classzone_idx >= cc.classzone_idx)
+ pgdat->kcompactd_classzone_idx = pgdat->nr_zones - 1;
}
void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx)
--
2.7.2
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