This is a note to let you know that I've just added the patch titled
mm/compaction: do not count migratepages when unnecessary
to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-compaction-do-not-count-migratepages-when-unnecessary.patch
and it can be found in the queue-3.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From f8c9301fa5a2a8b873c67f2a3d8230d5c13f61b7 Mon Sep 17 00:00:00 2001
From: Vlastimil Babka <[email protected]>
Date: Wed, 4 Jun 2014 16:08:32 -0700
Subject: mm/compaction: do not count migratepages when unnecessary
From: Vlastimil Babka <[email protected]>
commit f8c9301fa5a2a8b873c67f2a3d8230d5c13f61b7 upstream.
During compaction, update_nr_listpages() has been used to count remaining
non-migrated and free pages after a call to migrage_pages(). The
freepages counting has become unneccessary, and it turns out that
migratepages counting is also unnecessary in most cases.
The only situation when it's needed to count cc->migratepages is when
migrate_pages() returns with a negative error code. Otherwise, the
non-negative return value is the number of pages that were not migrated,
which is exactly the count of remaining pages in the cc->migratepages
list.
Furthermore, any non-zero count is only interesting for the tracepoint of
mm_compaction_migratepages events, because after that all remaining
unmigrated pages are put back and their count is set to 0.
This patch therefore removes update_nr_listpages() completely, and changes
the tracepoint definition so that the manual counting is done only when
the tracepoint is enabled, and only when migrate_pages() returns a
negative error code.
Furthermore, migrate_pages() and the tracepoints won't be called when
there's nothing to migrate. This potentially avoids some wasted cycles
and reduces the volume of uninteresting mm_compaction_migratepages events
where "nr_migrated=0 nr_failed=0". In the stress-highalloc mmtest, this
was about 75% of the events. The mm_compaction_isolate_migratepages event
is better for determining that nothing was isolated for migration, and
this one was just duplicating the info.
Signed-off-by: Vlastimil Babka <[email protected]>
Reviewed-by: Naoya Horiguchi <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Cc: Bartlomiej Zolnierkiewicz <[email protected]>
Acked-by: Michal Nazarewicz <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: Rik van Riel <[email protected]>
Acked-by: David Rientjes <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Mel Gorman <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
include/trace/events/compaction.h | 25 +++++++++++++++++++++----
mm/compaction.c | 31 +++++++------------------------
2 files changed, 28 insertions(+), 28 deletions(-)
--- a/include/trace/events/compaction.h
+++ b/include/trace/events/compaction.h
@@ -5,6 +5,7 @@
#define _TRACE_COMPACTION_H
#include <linux/types.h>
+#include <linux/list.h>
#include <linux/tracepoint.h>
#include <trace/events/gfpflags.h>
@@ -47,10 +48,11 @@ DEFINE_EVENT(mm_compaction_isolate_templ
TRACE_EVENT(mm_compaction_migratepages,
- TP_PROTO(unsigned long nr_migrated,
- unsigned long nr_failed),
+ TP_PROTO(unsigned long nr_all,
+ int migrate_rc,
+ struct list_head *migratepages),
- TP_ARGS(nr_migrated, nr_failed),
+ TP_ARGS(nr_all, migrate_rc, migratepages),
TP_STRUCT__entry(
__field(unsigned long, nr_migrated)
@@ -58,7 +60,22 @@ TRACE_EVENT(mm_compaction_migratepages,
),
TP_fast_assign(
- __entry->nr_migrated = nr_migrated;
+ unsigned long nr_failed = 0;
+ struct list_head *page_lru;
+
+ /*
+ * migrate_pages() returns either a non-negative number
+ * with the number of pages that failed migration, or an
+ * error code, in which case we need to count the remaining
+ * pages manually
+ */
+ if (migrate_rc >= 0)
+ nr_failed = migrate_rc;
+ else
+ list_for_each(page_lru, migratepages)
+ nr_failed++;
+
+ __entry->nr_migrated = nr_all - nr_failed;
__entry->nr_failed = nr_failed;
),
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -822,22 +822,6 @@ static void compaction_free(struct page
cc->nr_freepages++;
}
-/*
- * We cannot control nr_migratepages fully when migration is running as
- * migrate_pages() has no knowledge of of compact_control. When migration is
- * complete, we count the number of pages on the list by hand.
- */
-static void update_nr_listpages(struct compact_control *cc)
-{
- int nr_migratepages = 0;
- struct page *page;
-
- list_for_each_entry(page, &cc->migratepages, lru)
- nr_migratepages++;
-
- cc->nr_migratepages = nr_migratepages;
-}
-
/* possible outcome of isolate_migratepages */
typedef enum {
ISOLATE_ABORT, /* Abort compaction now */
@@ -1032,7 +1016,6 @@ static int compact_zone(struct zone *zon
migrate_prep_local();
while ((ret = compact_finished(zone, cc)) == COMPACT_CONTINUE) {
- unsigned long nr_migrate, nr_remaining;
int err;
switch (isolate_migratepages(zone, cc)) {
@@ -1047,20 +1030,20 @@ static int compact_zone(struct zone *zon
;
}
- nr_migrate = cc->nr_migratepages;
+ if (!cc->nr_migratepages)
+ continue;
+
err = migrate_pages(&cc->migratepages, compaction_alloc,
compaction_free, (unsigned long)cc, cc->mode,
MR_COMPACTION);
- update_nr_listpages(cc);
- nr_remaining = cc->nr_migratepages;
- trace_mm_compaction_migratepages(nr_migrate - nr_remaining,
- nr_remaining);
+ trace_mm_compaction_migratepages(cc->nr_migratepages, err,
+ &cc->migratepages);
- /* Release isolated pages not migrated */
+ /* All pages were either migrated or will be released */
+ cc->nr_migratepages = 0;
if (err) {
putback_movable_pages(&cc->migratepages);
- cc->nr_migratepages = 0;
/*
* migrate_pages() may return -ENOMEM when scanners meet
* and we want compact_finished() to detect it
Patches currently in stable-queue which might be from [email protected] are
queue-3.14/mm-filemap-move-radix-tree-hole-searching-here.patch
queue-3.14/mm-compaction-terminate-async-compaction-when-rescheduling.patch
queue-3.14/lib-radix-tree-add-radix_tree_delete_item.patch
queue-3.14/mm-compaction-properly-signal-and-act-upon-lock-and-need_sched-contention.patch
queue-3.14/mm-compaction-avoid-rescanning-pageblocks-in-isolate_freepages.patch
queue-3.14/mm-migration-add-destination-page-freeing-callback.patch
queue-3.14/mm-fs-prepare-for-non-page-entries-in-page-cache-radix-trees.patch
queue-3.14/mm-compaction-add-per-zone-migration-pfn-cache-for-async-compaction.patch
queue-3.14/mm-compaction-embed-migration-mode-in-compact_control.patch
queue-3.14/mm-shmem-save-one-radix-tree-lookup-when-truncating-swapped-pages.patch
queue-3.14/mm-page_alloc-prevent-migrate_reserve-pages-from-being-misplaced.patch
queue-3.14/mm-compaction-cleanup-isolate_freepages.patch
queue-3.14/mm-compaction-return-failed-migration-target-pages-back-to-freelist.patch
queue-3.14/mm-compaction-do-not-count-migratepages-when-unnecessary.patch
queue-3.14/mm-compaction-clean-up-unused-code-lines.patch
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