Proc - Page Type Info file
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.
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