On Tue, 23 Mar 2010 12:25:40 +0000
Mel Gorman <mel@xxxxxxxxx> 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@xxxxxxxxx>
> Reviewed-by: Minchan Kim <minchan.kim@xxxxxxxxx>
> Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
> Acked-by: Rik van Riel <riel@xxxxxxxxxx>
> ---
> 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 ?
Thanks,
-Kame
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