Re: [PATCH 3/3] mm/compaction: add an is_via_compact_memory helper function

From: Vlastimil Babka
Date: Wed Sep 23 2015 - 12:43:02 EST


On 09/16/2015 02:00 PM, Yaowei Bai wrote:
Introduce is_via_compact_memory helper function indicating compacting
via /proc/sys/vm/compact_memory to improve readability.

Note that it can also be through single node, i.e.
/sys/devices/system/node/node0/compact

is_manual_compaction() would perhaps be better name

To catch this situation in __compaction_suitable, use order as parameter
directly instead of using struct compact_control.

That can be fixed as well. Remove the test from __compaction_suitable(),
and in compact_zone(), do something like:
ret = is_manual_compaction() ? COMPACT_CONTINUE : compaction_suitable()

I think it's better since it's more explicit, but I understand others might feel differently.

This patch has no functional changes.

Signed-off-by: Yaowei Bai <bywxiaobai@xxxxxxx>
---
mm/compaction.c | 26 ++++++++++++++------------
1 file changed, 14 insertions(+), 12 deletions(-)

diff --git a/mm/compaction.c b/mm/compaction.c
index c5c627a..a8e6593 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1197,6 +1197,15 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
return cc->nr_migratepages ? ISOLATE_SUCCESS : ISOLATE_NONE;
}

+/*
+ * order == -1 is expected when compacting via
+ * /proc/sys/vm/compact_memory
+ */
+static inline bool is_via_compact_memory(int order)
+{
+ return order == -1;
+}
+
static int __compact_finished(struct zone *zone, struct compact_control *cc,
const int migratetype)
{
@@ -1223,11 +1232,7 @@ static int __compact_finished(struct zone *zone, struct compact_control *cc,
return COMPACT_COMPLETE;
}

- /*
- * order == -1 is expected when compacting via
- * /proc/sys/vm/compact_memory
- */
- if (cc->order == -1)
+ if (is_via_compact_memory(cc->order))
return COMPACT_CONTINUE;

/* Compaction run is not finished if the watermark is not met */
@@ -1290,11 +1295,7 @@ static unsigned long __compaction_suitable(struct zone *zone, int order,
int fragindex;
unsigned long watermark;

- /*
- * order == -1 is expected when compacting via
- * /proc/sys/vm/compact_memory
- */
- if (order == -1)
+ if (is_via_compact_memory(order))
return COMPACT_CONTINUE;

watermark = low_wmark_pages(zone);
@@ -1658,10 +1659,11 @@ static void __compact_pgdat(pg_data_t *pgdat, struct compact_control *cc)
* this makes sure we compact the whole zone regardless of
* cached scanner positions.
*/
- if (cc->order == -1)
+ if (is_via_compact_memory(cc->order))
__reset_isolation_suitable(zone);

- if (cc->order == -1 || !compaction_deferred(zone, cc->order))
+ if (is_via_compact_memory(cc->order) ||
+ !compaction_deferred(zone, cc->order))
compact_zone(zone, cc);

if (cc->order > 0) {


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