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SubjectRe: [PATCH 01/12] mm: Document /proc/pagetypeinfo
Date
> The memory compaction patches add details to pagetypeinfo that are not
> obvious and need to be documented. In preparation for this, document
> what is already in /proc/pagetypeinfo.
>
> Signed-off-by: Mel Gorman <mel@csn.ul.ie>

Looks nicer.
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>

> ---
> Documentation/filesystems/proc.txt | 45 +++++++++++++++++++++++++++++++++++-
> 1 files changed, 44 insertions(+), 1 deletions(-)
>
> diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
> index 0d07513..1829dfb 100644
> --- a/Documentation/filesystems/proc.txt
> +++ b/Documentation/filesystems/proc.txt
> @@ -430,6 +430,7 @@ Table 1-5: Kernel info in /proc
> modules List of loaded modules
> mounts Mounted filesystems
> net Networking info (see text)
> + pagetypeinfo Additional page allocator information (see text) (2.5)
> partitions Table of partitions known to the system
> pci Deprecated info of PCI bus (new way -> /proc/bus/pci/,
> decoupled by lspci (2.4)
> @@ -584,7 +585,7 @@ Node 0, zone DMA 0 4 5 4 4 3 ...
> Node 0, zone Normal 1 0 0 1 101 8 ...
> Node 0, zone HighMem 2 0 0 1 1 0 ...
>
> -Memory fragmentation is a problem under some workloads, and buddyinfo is a
> +External fragmentation is a problem under some workloads, and buddyinfo is a
> useful tool for helping diagnose these problems. Buddyinfo will give you a
> clue as to how big an area you can safely allocate, or why a previous
> allocation failed.
> @@ -594,6 +595,48 @@ available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in
> 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.
> +
> +> cat /proc/pagetypeinfo
> +Page block order: 9
> +Pages per block: 512
> +
> +Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10
> +Node 0, zone DMA, type Unmovable 0 0 0 1 1 1 1 1 1 1 0
> +Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0
> +Node 0, zone DMA, type Movable 1 1 2 1 2 1 1 0 1 0 2
> +Node 0, zone DMA, type Reserve 0 0 0 0 0 0 0 0 0 1 0
> +Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0
> +Node 0, zone DMA32, type Unmovable 103 54 77 1 1 1 11 8 7 1 9
> +Node 0, zone DMA32, type Reclaimable 0 0 2 1 0 0 0 0 1 0 0
> +Node 0, zone DMA32, type Movable 169 152 113 91 77 54 39 13 6 1 452
> +Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0
> +Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0
> +
> +Number of blocks type Unmovable Reclaimable Movable Reserve Isolate
> +Node 0, zone DMA 2 0 5 1 0
> +Node 0, zone DMA32 41 6 967 2 0
> +
> +Fragmentation avoidance in the kernel works by grouping pages of different
> +migrate types into the same contiguous regions of memory called page blocks.
> +A page block is typically the size of the default hugepage size e.g. 2MB on
> +X86-64. By keeping pages grouped based on their ability to move, the kernel
> +can reclaim pages within a page block to satisfy a high-order allocation.
> +
> +The pagetypinfo begins with information on the size of a page block. It
> +then gives the same type of information as buddyinfo except broken down
> +by migrate-type and finishes with details on how many page blocks of each
> +type exist.
> +
> +If min_free_kbytes has been tuned correctly (recommendations made by hugeadm
> +from libhugetlbfs http://sourceforge.net/projects/libhugetlbfs/), one can
> +make an estimate of the likely number of huge pages that can be allocated
> +at a given point in time. All the "Movable" blocks should be allocatable
> +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.
> +
> ..............................................................................
>
> meminfo:
> --
> 1.6.5
>





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