mm: export unusable free space index via debugfs
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. 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 /sys/kernel/debug/extfrag/unusable_index. > cat /sys/kernel/debug/extfrag/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 [akpm@linux-foundation.org: Fix allnoconfig] Signed-off-by: NMel Gorman <mel@csn.ul.ie> Reviewed-by: NMinchan Kim <minchan.kim@gmail.com> Reviewed-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Reviewed-by: NChristoph Lameter <cl@linux-foundation.org> Cc: Rik van Riel <riel@redhat.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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