This reverts commit 7db8889a (mm: have order 0 compaction start off
where it left) and commit de74f1cc (mm: have order 0 compaction start
near a pageblock with free pages). These patches were a good idea and
tests confirmed that they massively reduced the amount of scanning but
the implementation is complex and tricky to understand. A later patch
will cache what pageblocks should be skipped and reimplements the
concept of compact_cached_free_pfn on top for both migration and
free scanners.
Signed-off-by: Mel Gorman mgor...@suse.de
---
include/linux/mmzone.h |4 ---
mm/compaction.c| 65
mm/internal.h |6 -
mm/page_alloc.c|5
4 files changed, 5 insertions(+), 75 deletions(-)
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 2daa54f..603d0b5 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -368,10 +368,6 @@ struct zone {
*/
spinlock_t lock;
int all_unreclaimable; /* All pages pinned */
-#if defined CONFIG_COMPACTION || defined CONFIG_CMA
- /* pfn where the last incremental compaction isolated free pages */
- unsigned long compact_cached_free_pfn;
-#endif
#ifdef CONFIG_MEMORY_HOTPLUG
/* see spanned/present_pages for more description */
seqlock_t span_seqlock;
diff --git a/mm/compaction.c b/mm/compaction.c
index 70c7cbd..6058822 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -481,20 +481,6 @@ next_pageblock:
#endif /* CONFIG_COMPACTION || CONFIG_CMA */
#ifdef CONFIG_COMPACTION
/*
- * Returns the start pfn of the last page block in a zone. This is the
starting
- * point for full compaction of a zone. Compaction searches for free pages
from
- * the end of each zone, while isolate_freepages_block scans forward inside
each
- * page block.
- */
-static unsigned long start_free_pfn(struct zone *zone)
-{
- unsigned long free_pfn;
- free_pfn = zone-zone_start_pfn + zone-spanned_pages;
- free_pfn = ~(pageblock_nr_pages-1);
- return free_pfn;
-}
-
-/*
* Based on information in the current compact_control, find blocks
* suitable for isolating free pages from and then isolate them.
*/
@@ -562,19 +548,8 @@ static void isolate_freepages(struct zone *zone,
* looking for free pages, the search will restart here as
* page migration may have returned some pages to the allocator
*/
- if (isolated) {
+ if (isolated)
high_pfn = max(high_pfn, pfn);
-
- /*
-* If the free scanner has wrapped, update
-* compact_cached_free_pfn to point to the highest
-* pageblock with free pages. This reduces excessive
-* scanning of full pageblocks near the end of the
-* zone
-*/
- if (cc-order 0 cc-wrapped)
- zone-compact_cached_free_pfn = high_pfn;
- }
}
/* split_free_page does not map the pages */
@@ -582,11 +557,6 @@ static void isolate_freepages(struct zone *zone,
cc-free_pfn = high_pfn;
cc-nr_freepages = nr_freepages;
-
- /* If compact_cached_free_pfn is reset then set it now */
- if (cc-order 0 !cc-wrapped
- zone-compact_cached_free_pfn == start_free_pfn(zone))
- zone-compact_cached_free_pfn = high_pfn;
}
/*
@@ -682,26 +652,8 @@ static int compact_finished(struct zone *zone,
if (fatal_signal_pending(current))
return COMPACT_PARTIAL;
- /*
-* A full (order == -1) compaction run starts at the beginning and
-* end of a zone; it completes when the migrate and free scanner meet.
-* A partial (order 0) compaction can start with the free scanner
-* at a random point in the zone, and may have to restart.
-*/
- if (cc-free_pfn = cc-migrate_pfn) {
- if (cc-order 0 !cc-wrapped) {
- /* We started partway through; restart at the end. */
- unsigned long free_pfn = start_free_pfn(zone);
- zone-compact_cached_free_pfn = free_pfn;
- cc-free_pfn = free_pfn;
- cc-wrapped = 1;
- return COMPACT_CONTINUE;
- }
- return COMPACT_COMPLETE;
- }
-
- /* We wrapped around and ended up where we started. */
- if (cc-wrapped cc-free_pfn = cc-start_free_pfn)
+ /* Compaction run completes if the migrate and free scanner meet */
+ if (cc-free_pfn = cc-migrate_pfn)
return COMPACT_COMPLETE;
/*
@@ -799,15 +751,8 @@ static int compact_zone(struct zone *zone, struct
