Eric Lee / smarc-ti-linux-kernel

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Commit 5e4084a627820bd6a8d94bca6acb878e5308716c

Authored by Vlastimil Babka
Committed by Jiri Slaby
1 parent 0d9b792442
Exists in ti-linux-3.12.y and in 2 other branches newt-ti-linux-3.12.y, smarc-ti-linux-3.12.y

mm/compaction: do not count migratepages when unnecessary 

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 <vbabka@suse.cz>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Rik van Riel <riel@redhat.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>

Showing 2 changed files with 28 additions and 28 deletions Side-by-side Diff

include/trace/events/compaction.h
Diff comments   View file @ 5e4084a
... ... @@ -5,6 +5,7 @@
5 5 #define _TRACE_COMPACTION_H
6 6  
7 7 #include <linux/types.h>
  8 +#include <linux/list.h>
8 9 #include <linux/tracepoint.h>
9 10 #include <trace/events/gfpflags.h>
10 11  
11 12  
... ... @@ -47,10 +48,11 @@
47 48  
48 49 TRACE_EVENT(mm_compaction_migratepages,
49 50  
50   - TP_PROTO(unsigned long nr_migrated,
51   - unsigned long nr_failed),
  51 + TP_PROTO(unsigned long nr_all,
  52 + int migrate_rc,
  53 + struct list_head *migratepages),
52 54  
53   - TP_ARGS(nr_migrated, nr_failed),
  55 + TP_ARGS(nr_all, migrate_rc, migratepages),
54 56  
55 57 TP_STRUCT__entry(
56 58 __field(unsigned long, nr_migrated)
... ... @@ -58,7 +60,22 @@
58 60 ),
59 61  
60 62 TP_fast_assign(
61   - __entry->nr_migrated = nr_migrated;
  63 + unsigned long nr_failed = 0;
  64 + struct list_head *page_lru;
  65 +
  66 + /*
  67 + * migrate_pages() returns either a non-negative number
  68 + * with the number of pages that failed migration, or an
  69 + * error code, in which case we need to count the remaining
  70 + * pages manually
  71 + */
  72 + if (migrate_rc >= 0)
  73 + nr_failed = migrate_rc;
  74 + else
  75 + list_for_each(page_lru, migratepages)
  76 + nr_failed++;
  77 +
  78 + __entry->nr_migrated = nr_all - nr_failed;
62 79 __entry->nr_failed = nr_failed;
63 80 ),
64 81  
... ... @@ -820,22 +820,6 @@
820 820 cc->nr_freepages++;
821 821 }
822 822  
823   -/*
824   - * We cannot control nr_migratepages fully when migration is running as
825   - * migrate_pages() has no knowledge of of compact_control. When migration is
826   - * complete, we count the number of pages on the list by hand.
827   - */
828   -static void update_nr_listpages(struct compact_control *cc)
829   -{
830   - int nr_migratepages = 0;
831   - struct page *page;
832   -
833   - list_for_each_entry(page, &cc->migratepages, lru)
834   - nr_migratepages++;
835   -
836   - cc->nr_migratepages = nr_migratepages;
837   -}
838   -
839 823 /* possible outcome of isolate_migratepages */
840 824 typedef enum {
841 825 ISOLATE_ABORT, /* Abort compaction now */
... ... @@ -1030,7 +1014,6 @@
1030 1014 migrate_prep_local();
1031 1015  
1032 1016 while ((ret = compact_finished(zone, cc)) == COMPACT_CONTINUE) {
1033   - unsigned long nr_migrate, nr_remaining;
1034 1017 int err;
1035 1018  
1036 1019 switch (isolate_migratepages(zone, cc)) {
1037 1020  
1038 1021  
1039 1022  
1040 1023  
... ... @@ -1045,20 +1028,20 @@
1045 1028 ;
1046 1029 }
1047 1030  
1048   - nr_migrate = cc->nr_migratepages;
  1031 + if (!cc->nr_migratepages)
  1032 + continue;
  1033 +
1049 1034 err = migrate_pages(&cc->migratepages, compaction_alloc,
1050 1035 compaction_free, (unsigned long)cc, cc->mode,
1051 1036 MR_COMPACTION);
1052   - update_nr_listpages(cc);
1053   - nr_remaining = cc->nr_migratepages;
1054 1037  
1055   - trace_mm_compaction_migratepages(nr_migrate - nr_remaining,
1056   - nr_remaining);
  1038 + trace_mm_compaction_migratepages(cc->nr_migratepages, err,
  1039 + &cc->migratepages);
1057 1040  
1058   - /* Release isolated pages not migrated */
  1041 + /* All pages were either migrated or will be released */
  1042 + cc->nr_migratepages = 0;
1059 1043 if (err) {
1060 1044 putback_movable_pages(&cc->migratepages);
1061   - cc->nr_migratepages = 0;
1062 1045 /*
1063 1046 * migrate_pages() may return -ENOMEM when scanners meet
1064 1047 * and we want compact_finished() to detect it