[PATCH 03/14] mm, compaction: Remove last_migrated_pfn from compact_control

Mel Gorman
2018-12-14T23:03:17Z

The last_migrated_pfn field is a bit dubious as to whether it really helps
but either way, the information from it can be inferred without increasing
the size of compact_control so remove the field.

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
---
mm/compaction.c | 25 +++++++++----------------
mm/internal.h | 1 -
2 files changed, 9 insertions(+), 17 deletions(-)

diff --git a/mm/compaction.c b/mm/compaction.c
index ef29490b0f46..fb4d9f52ed56 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -886,15 +886,6 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
cc->nr_migratepages++;
nr_isolated++;

- /*
- * Record where we could have freed pages by migration and not
- * yet flushed them to buddy allocator.
- * - this is the lowest page that was isolated and likely be
- * then freed by migration.
- */
- if (!cc->last_migrated_pfn)
- cc->last_migrated_pfn = low_pfn;
-
/* Avoid isolating too much */
if (cc->nr_migratepages == COMPACT_CLUSTER_MAX) {
++low_pfn;
@@ -918,7 +909,6 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
}
putback_movable_pages(&cc->migratepages);
cc->nr_migratepages = 0;
- cc->last_migrated_pfn = 0;
nr_isolated = 0;
}

@@ -1539,6 +1529,7 @@ static enum compact_result compact_zone(struct zone *zone, struct compact_contro
enum compact_result ret;
unsigned long start_pfn = zone->zone_start_pfn;
unsigned long end_pfn = zone_end_pfn(zone);
+ unsigned long last_migrated_pfn;
const bool sync = cc->mode != MIGRATE_ASYNC;

cc->migratetype = gfpflags_to_migratetype(cc->gfp_mask);
@@ -1584,7 +1575,7 @@ static enum compact_result compact_zone(struct zone *zone, struct compact_contro
cc->whole_zone = true;
}

- cc->last_migrated_pfn = 0;
+ last_migrated_pfn = 0;

trace_mm_compaction_begin(start_pfn, cc->migrate_pfn,
cc->free_pfn, end_pfn, sync);
@@ -1593,12 +1584,14 @@ static enum compact_result compact_zone(struct zone *zone, struct compact_contro

while ((ret = compact_finished(zone, cc)) == COMPACT_CONTINUE) {
int err;
+ unsigned long start_pfn = cc->migrate_pfn;

switch (isolate_migratepages(zone, cc)) {
case ISOLATE_ABORT:
ret = COMPACT_CONTENDED;
putback_movable_pages(&cc->migratepages);
cc->nr_migratepages = 0;
+ last_migrated_pfn = 0;
goto out;
case ISOLATE_NONE:
/*
@@ -1608,6 +1601,7 @@ static enum compact_result compact_zone(struct zone *zone, struct compact_contro
*/
goto check_drain;
case ISOLATE_SUCCESS:
+ last_migrated_pfn = start_pfn;
;
}

@@ -1639,8 +1633,7 @@ static enum compact_result compact_zone(struct zone *zone, struct compact_contro
cc->migrate_pfn = block_end_pfn(
cc->migrate_pfn - 1, cc->order);
/* Draining pcplists is useless in this case */
- cc->last_migrated_pfn = 0;
-
+ last_migrated_pfn = 0;
}
}

@@ -1652,18 +1645,18 @@ static enum compact_result compact_zone(struct zone *zone, struct compact_contro
* compact_finished() can detect immediately if allocation
* would succeed.
*/
- if (cc->order > 0 && cc->last_migrated_pfn) {
+ if (cc->order > 0 && last_migrated_pfn) {
int cpu;
unsigned long current_block_start =
block_start_pfn(cc->migrate_pfn, cc->order);

- if (cc->last_migrated_pfn < current_block_start) {
+ if (last_migrated_pfn < current_block_start) {
cpu = get_cpu();
lru_add_drain_cpu(cpu);
drain_local_pages(zone);
put_cpu();
/* No more flushing until we migrate again */
- cc->last_migrated_pfn = 0;
+ last_migrated_pfn = 0;
}
}

diff --git a/mm/internal.h b/mm/internal.h
index 867af5425432..f40d06d70683 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -188,7 +188,6 @@ struct compact_control {
unsigned int nr_migratepages; /* Number of pages to migrate */
unsigned long free_pfn; /* isolate_freepages search base */
unsigned long migrate_pfn; /* isolate_migratepages search base */
- unsigned long last_migrated_pfn;/* Not yet flushed page being freed */
struct zone *zone;
unsigned long total_migrate_scanned;
unsigned long total_free_scanned;
--
2.16.4