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    SubjectRe: [PATCH 05/11] Export unusable free space index via /proc/unusable_index
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    Hi, Kame.

    On Wed, Mar 24, 2010 at 9:03 AM, KAMEZAWA Hiroyuki
    <kamezawa.hiroyu@jp.fujitsu.com> wrote:
    > On Tue, 23 Mar 2010 12:25:40 +0000
    > Mel Gorman <mel@csn.ul.ie> wrote:
    >
    >> Unusable free space index is a measure of external fragmentation that
    >> takes the allocation size into account. For the most part, the huge page
    >> size will be the size of interest but not necessarily so it is exported
    >> on a per-order and per-zone basis via /proc/unusable_index.
    >>
    >> The index is a value between 0 and 1. It can be expressed as a
    >> percentage by multiplying by 100 as documented in
    >> Documentation/filesystems/proc.txt.
    >>
    >> Signed-off-by: Mel Gorman <mel@csn.ul.ie>
    >> Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
    >> Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
    >> Acked-by: Rik van Riel <riel@redhat.com>
    >> ---
    >>  Documentation/filesystems/proc.txt |   13 ++++-
    >>  mm/vmstat.c                        |  120 +++++++++++++++++++++++++++++++++
    >>  2 files changed, 132 insertions(+), 1 deletions(-)
    >>
    >> diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
    >> index 5e132b5..5c4b0fb 100644
    >> --- a/Documentation/filesystems/proc.txt
    >> +++ b/Documentation/filesystems/proc.txt
    >> @@ -452,6 +452,7 @@ Table 1-5: Kernel info in /proc
    >>   sys         See chapter 2
    >>   sysvipc     Info of SysVIPC Resources (msg, sem, shm)               (2.4)
    >>   tty      Info of tty drivers
    >> + unusable_index Additional page allocator information (see text)(2.5)
    >>   uptime      System uptime
    >>   version     Kernel version
    >>   video            bttv info of video resources                       (2.4)
    >> @@ -609,7 +610,7 @@ ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE
    >>  available in ZONE_NORMAL, etc...
    >>
    >>  More information relevant to external fragmentation can be found in
    >> -pagetypeinfo.
    >> +pagetypeinfo and unusable_index
    >>
    >>  > cat /proc/pagetypeinfo
    >>  Page block order: 9
    >> @@ -650,6 +651,16 @@ unless memory has been mlock()'d. Some of the Reclaimable blocks should
    >>  also be allocatable although a lot of filesystem metadata may have to be
    >>  reclaimed to achieve this.
    >>
    >> +> cat /proc/unusable_index
    >> +Node 0, zone      DMA 0.000 0.000 0.000 0.001 0.005 0.013 0.021 0.037 0.037 0.101 0.230
    >> +Node 0, zone   Normal 0.000 0.000 0.000 0.001 0.002 0.002 0.005 0.015 0.028 0.028 0.054
    >> +
    >> +The unusable free space index measures how much of the available free
    >> +memory cannot be used to satisfy an allocation of a given size and is a
    >> +value between 0 and 1. The higher the value, the more of free memory is
    >> +unusable and by implication, the worse the external fragmentation is. This
    >> +can be expressed as a percentage by multiplying by 100.
    >> +
    >>  ..............................................................................
    >>
    >>  meminfo:
    >> diff --git a/mm/vmstat.c b/mm/vmstat.c
    >> index 7f760cb..ca42e10 100644
    >> --- a/mm/vmstat.c
    >> +++ b/mm/vmstat.c
    >> @@ -453,6 +453,106 @@ static int frag_show(struct seq_file *m, void *arg)
    >>       return 0;
    >>  }
    >>
    >> +
    >> +struct contig_page_info {
    >> +     unsigned long free_pages;
    >> +     unsigned long free_blocks_total;
    >> +     unsigned long free_blocks_suitable;
    >> +};
    >> +
    >> +/*
    >> + * Calculate the number of free pages in a zone, how many contiguous
    >> + * pages are free and how many are large enough to satisfy an allocation of
    >> + * the target size. Note that this function makes to attempt to estimate
    >> + * how many suitable free blocks there *might* be if MOVABLE pages were
    >> + * migrated. Calculating that is possible, but expensive and can be
    >> + * figured out from userspace
    >> + */
    >> +static void fill_contig_page_info(struct zone *zone,
    >> +                             unsigned int suitable_order,
    >> +                             struct contig_page_info *info)
    >> +{
    >> +     unsigned int order;
    >> +
    >> +     info->free_pages = 0;
    >> +     info->free_blocks_total = 0;
    >> +     info->free_blocks_suitable = 0;
    >> +
    >> +     for (order = 0; order < MAX_ORDER; order++) {
    >> +             unsigned long blocks;
    >> +
    >> +             /* Count number of free blocks */
    >> +             blocks = zone->free_area[order].nr_free;
    >> +             info->free_blocks_total += blocks;
    >
    > ....for what this free_blocks_total is ?

    It's used by fragmentation_index in [06/11].

    >
    > Thanks,
    > -Kame
    >
    >



    --
    Kind regards,
    Minchan Kim
    --
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