lkml.org 
[lkml]   [2014]   [May]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH v2 1/2] mm/compaction: do not count migratepages when unnecessary
    Date
    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>
    Cc: Michal Nazarewicz <mina86@mina86.com>
    Cc: Christoph Lameter <cl@linux.com>
    Cc: Rik van Riel <riel@redhat.com>
    ---
    v2: checkpack and other non-functional fixes suggested by Naoya Horiguchi

    include/trace/events/compaction.h | 26 ++++++++++++++++++++++----
    mm/compaction.c | 31 +++++++------------------------
    2 files changed, 29 insertions(+), 28 deletions(-)

    diff --git a/include/trace/events/compaction.h b/include/trace/events/compaction.h
    index 06f544e..aacaf0f 100644
    --- a/include/trace/events/compaction.h
    +++ b/include/trace/events/compaction.h
    @@ -5,7 +5,9 @@
    #define _TRACE_COMPACTION_H

    #include <linux/types.h>
    +#include <linux/list.h>
    #include <linux/tracepoint.h>
    +#include <linux/mm_types.h>
    #include <trace/events/gfpflags.h>

    DECLARE_EVENT_CLASS(mm_compaction_isolate_template,
    @@ -47,10 +49,11 @@ DEFINE_EVENT(mm_compaction_isolate_template, mm_compaction_isolate_freepages,

    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 +61,22 @@ TRACE_EVENT(mm_compaction_migratepages,
    ),

    TP_fast_assign(
    - __entry->nr_migrated = nr_migrated;
    + unsigned long nr_failed = 0;
    + struct page *page;
    +
    + /*
    + * 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_entry(page, migratepages, lru)
    + nr_failed++;
    +
    + __entry->nr_migrated = nr_all - nr_failed;
    __entry->nr_failed = nr_failed;
    ),

    diff --git a/mm/compaction.c b/mm/compaction.c
    index 6f4b218..383d562 100644
    --- a/mm/compaction.c
    +++ b/mm/compaction.c
    @@ -819,22 +819,6 @@ static void compaction_free(struct page *page, unsigned long data)
    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 */
    @@ -1029,7 +1013,6 @@ static int compact_zone(struct zone *zone, struct compact_control *cc)
    migrate_prep_local();

    while ((ret = compact_finished(zone, cc)) == COMPACT_CONTINUE) {
    - unsigned long nr_migrate, nr_remaining;
    int err;

    switch (isolate_migratepages(zone, cc)) {
    @@ -1044,20 +1027,20 @@ static int compact_zone(struct zone *zone, struct compact_control *cc)
    ;
    }

    - 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
    --
    1.8.4.5


    \
     
     \ /
      Last update: 2014-05-07 14:21    [W:4.164 / U:0.092 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site