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-rw-r--r--mm/compaction.c89
1 files changed, 55 insertions, 34 deletions
diff --git a/mm/compaction.c b/mm/compaction.c
index 20011a8..8fe917e 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -384,10 +384,62 @@ static int compact_finished(struct zone *zone,
return COMPACT_CONTINUE;
}
+/*
+ * compaction_suitable: Is this suitable to run compaction on this zone now?
+ * Returns
+ * COMPACT_SKIPPED - If there are too few free pages for compaction
+ * COMPACT_PARTIAL - If the allocation would succeed without compaction
+ * COMPACT_CONTINUE - If compaction should run now
+ */
+unsigned long compaction_suitable(struct zone *zone, int order)
+{
+ int fragindex;
+ unsigned long watermark;
+
+ /*
+ * Watermarks for order-0 must be met for compaction. Note the 2UL.
+ * This is because during migration, copies of pages need to be
+ * allocated and for a short time, the footprint is higher
+ */
+ watermark = low_wmark_pages(zone) + (2UL << order);
+ if (!zone_watermark_ok(zone, 0, watermark, 0, 0))
+ return COMPACT_SKIPPED;
+
+ /*
+ * fragmentation index determines if allocation failures are due to
+ * low memory or external fragmentation
+ *
+ * index of -1 implies allocations might succeed dependingon watermarks
+ * index towards 0 implies failure is due to lack of memory
+ * index towards 1000 implies failure is due to fragmentation
+ *
+ * Only compact if a failure would be due to fragmentation.
+ */
+ fragindex = fragmentation_index(zone, order);
+ if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold)
+ return COMPACT_SKIPPED;
+
+ if (fragindex == -1 && zone_watermark_ok(zone, order, watermark, 0, 0))
+ return COMPACT_PARTIAL;
+
+ return COMPACT_CONTINUE;
+}
+
static int compact_zone(struct zone *zone, struct compact_control *cc)
{
int ret;
+ ret = compaction_suitable(zone, cc->order);
+ switch (ret) {
+ case COMPACT_PARTIAL:
+ case COMPACT_SKIPPED:
+ /* Compaction is likely to fail */
+ return ret;
+ case COMPACT_CONTINUE:
+ /* Fall through to compaction */
+ ;
+ }
+
/* Setup to move all movable pages to the end of the zone */
cc->migrate_pfn = zone->zone_start_pfn;
cc->free_pfn = cc->migrate_pfn + zone->spanned_pages;
@@ -429,7 +481,7 @@ static int compact_zone(struct zone *zone, struct compact_control *cc)
return ret;
}
-static unsigned long compact_zone_order(struct zone *zone,
+unsigned long compact_zone_order(struct zone *zone,
int order, gfp_t gfp_mask)
{
struct compact_control cc = {
@@ -462,7 +514,6 @@ unsigned long try_to_compact_pages(struct zonelist *zonelist,
enum zone_type high_zoneidx = gfp_zone(gfp_mask);
int may_enter_fs = gfp_mask & __GFP_FS;
int may_perform_io = gfp_mask & __GFP_IO;
- unsigned long watermark;
struct zoneref *z;
struct zone *zone;
int rc = COMPACT_SKIPPED;
@@ -480,43 +531,13 @@ unsigned long try_to_compact_pages(struct zonelist *zonelist,
/* Compact each zone in the list */
for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx,
nodemask) {
- int fragindex;
int status;
- /*
- * Watermarks for order-0 must be met for compaction. Note
- * the 2UL. This is because during migration, copies of
- * pages need to be allocated and for a short time, the
- * footprint is higher
- */
- watermark = low_wmark_pages(zone) + (2UL << order);
- if (!zone_watermark_ok(zone, 0, watermark, 0, 0))
- continue;
-
- /*
- * fragmentation index determines if allocation failures are
- * due to low memory or external fragmentation
- *
- * index of -1 implies allocations might succeed depending
- * on watermarks
- * index towards 0 implies failure is due to lack of memory
- * index towards 1000 implies failure is due to fragmentation
- *
- * Only compact if a failure would be due to fragmentation.
- */
- fragindex = fragmentation_index(zone, order);
- if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold)
- continue;
-
- if (fragindex == -1 && zone_watermark_ok(zone, order, watermark, 0, 0)) {
- rc = COMPACT_PARTIAL;
- break;
- }
-
status = compact_zone_order(zone, order, gfp_mask);
rc = max(status, rc);
- if (zone_watermark_ok(zone, order, watermark, 0, 0))
+ /* If a normal allocation would succeed, stop compacting */
+ if (zone_watermark_ok(zone, order, low_wmark_pages(zone), 0, 0))
break;
}
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