2015-03-19 오후 6:01에 Vlastimil Babka 이(가) 쓴 글:
On 03/19/2015 09:52 AM, Gioh Kim wrote:
2015-03-19 오후 5:41에 Vlastimil Babka 이(가) 쓴 글:
On 03/19/2015 06:30 AM, Gioh Kim wrote:
The code below this comment already does the initialization if the cached values
are outside zone boundaries (e.g. due to not being initialized). So if I go
through what your __reset_isolation_suitable(zone) call possibly fixes:
- the code below comment should take care of zone->compact_cached_migrate_pfn
and zone->compact_cached_free_pfn.
- the value of zone->compact_blockskip_flush shouldn't affect whether compaction
is done.
- the state of pageblock_skip bits shouldn't matter for compaction via
/proc/sys... as that sets ignore_skip_hint = true
It might be perhaps possible that the cached scanner positions are close to
meeting and compaction occurs but doesn't process much. That would be also true
if both were zero, but at least on my x86 system, lowest zone's start_pfn is 1
so that would be detected and corrected. Maybe it is zero on yours though? (ARM?).
YES, it is. As comment above, my platform is based on ARM.
Ah, I see.
zone's start_pfn is 0.
OK, good to know that's possible. In that case it's clear that the proper
initialization doesn't happen, and __compact_finished() decides that scanners
have already met at pfn 0.
So in any case, the problem should be identified in more detail so we know the
fix is not accidental. It could be also worthwile to always reset scanner
positions when doing a /proc triggered compaction, so it's not depending on what
happened before.
Excuse my poor english.
I cannot catch exactly what you want.
Is this what you want? This resets the position if compaction is started via /proc.
Yes that's right, but..
diff --git a/mm/compaction.c b/mm/compaction.c
index 8c0d945..827ec06 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1587,8 +1587,10 @@ static void __compact_pgdat(pg_data_t *pgdat, struct compact_control *cc)
INIT_LIST_HEAD(&cc->freepages);
INIT_LIST_HEAD(&cc->migratepages);
- if (cc->order == -1 || !compaction_deferred(zone, cc->order))
+ if (cc->order == -1 || !compaction_deferred(zone, cc->order)) {
+ __reset_isolation_suitable(zone);
This will also trigger reset when called from kswapd through compact_pgdat() and
!compaction_deferred() is true.
The reset should be restricted to cc->order == -1 which only happens from /proc
trigger.
compact_zone(zone, cc);
+ }
if (cc->order > 0) {
if (zone_watermark_ok(zone, cc->order,
I've not been familiar with compaction code.
I think cc->order is -1 only if __compact_pgdat is called via /proc.
This is ugly but I don't have better solution.
Do you have better idea?
diff --git a/mm/compaction.c b/mm/compaction.c
index 8c0d945..5b4e255 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1587,6 +1587,9 @@ static void __compact_pgdat(pg_data_t *pgdat, struct compact_control *cc)
INIT_LIST_HEAD(&cc->freepages);
INIT_LIST_HEAD(&cc->migratepages);
+ if (cc->order == -1)
+ __reset_isolation_suitable(zone);
+
if (cc->order == -1 || !compaction_deferred(zone, cc->order))
compact_zone(zone, cc);
--
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