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@@ -438,6 +438,7 @@ Table 1-5: Kernel info in /proc
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modules List of loaded modules
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mounts Mounted filesystems
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net Networking info (see text)
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+ pagetypeinfo Additional page allocator information (see text) (2.5)
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partitions Table of partitions known to the system
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pci Deprecated info of PCI bus (new way -> /proc/bus/pci/,
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decoupled by lspci (2.4)
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@@ -592,7 +593,7 @@ Node 0, zone DMA 0 4 5 4 4 3 ...
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Node 0, zone Normal 1 0 0 1 101 8 ...
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Node 0, zone HighMem 2 0 0 1 1 0 ...
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-Memory fragmentation is a problem under some workloads, and buddyinfo is a
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+External fragmentation is a problem under some workloads, and buddyinfo is a
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useful tool for helping diagnose these problems. Buddyinfo will give you a
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clue as to how big an area you can safely allocate, or why a previous
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allocation failed.
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@@ -602,6 +603,48 @@ available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in
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ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE
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available in ZONE_NORMAL, etc...
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+More information relevant to external fragmentation can be found in
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+pagetypeinfo.
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+
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+> cat /proc/pagetypeinfo
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+Page block order: 9
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+Pages per block: 512
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+
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+Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10
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+Node 0, zone DMA, type Unmovable 0 0 0 1 1 1 1 1 1 1 0
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+Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0
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+Node 0, zone DMA, type Movable 1 1 2 1 2 1 1 0 1 0 2
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+Node 0, zone DMA, type Reserve 0 0 0 0 0 0 0 0 0 1 0
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+Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0
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+Node 0, zone DMA32, type Unmovable 103 54 77 1 1 1 11 8 7 1 9
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+Node 0, zone DMA32, type Reclaimable 0 0 2 1 0 0 0 0 1 0 0
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+Node 0, zone DMA32, type Movable 169 152 113 91 77 54 39 13 6 1 452
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+Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0
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+Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0
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+
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+Number of blocks type Unmovable Reclaimable Movable Reserve Isolate
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+Node 0, zone DMA 2 0 5 1 0
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+Node 0, zone DMA32 41 6 967 2 0
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+
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+Fragmentation avoidance in the kernel works by grouping pages of different
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+migrate types into the same contiguous regions of memory called page blocks.
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+A page block is typically the size of the default hugepage size e.g. 2MB on
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+X86-64. By keeping pages grouped based on their ability to move, the kernel
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+can reclaim pages within a page block to satisfy a high-order allocation.
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+
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+The pagetypinfo begins with information on the size of a page block. It
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+then gives the same type of information as buddyinfo except broken down
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+by migrate-type and finishes with details on how many page blocks of each
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+type exist.
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+
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+If min_free_kbytes has been tuned correctly (recommendations made by hugeadm
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+from libhugetlbfs http://sourceforge.net/projects/libhugetlbfs/), one can
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+make an estimate of the likely number of huge pages that can be allocated
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+at a given point in time. All the "Movable" blocks should be allocatable
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+unless memory has been mlock()'d. Some of the Reclaimable blocks should
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+also be allocatable although a lot of filesystem metadata may have to be
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+reclaimed to achieve this.
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+
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..............................................................................
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meminfo:
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Mel Gorman