[PATCH 0/8][for -mm] mem_notify v6

[KOSAKI Motohiro]

Hi

The /dev/mem_notify is low memory notification device.
it can avoid swappness and oom by cooperationg with the user process.

the Linux Today article is very nice description. (great works by Jake Edge)
http://www.linuxworld.com/news/2008/020508-kernel.html

<quoted>
When memory gets tight, it is quite possible that applications have memory
allocated—often caches for better performance—that they could free.
After all, it is generally better to lose some performance than to face the
consequences of being chosen by the OOM killer.
But, currently, there is no way for a process to know that the kernel is
feeling memory pressure.
The patch provides a way for interested programs to monitor the /dev/mem_notify
 file to be notified if memory starts to run low.
</quoted>


You need not be annoyed by OOM any longer :)
please any comments!

patch list
       [1/8] introduce poll_wait_exclusive() new API
       [2/8] introduce wake_up_locked_nr() new API
       [3/8] introduce /dev/mem_notify new device (the core of this
patch series)
       [4/8] memory_pressure_notify() caller
       [5/8] add new mem_notify field to /proc/zoneinfo
       [6/8] (optional) fixed incorrect shrink_zone
       [7/8] ignore very small zone for prevent incorrect low mem notify.
       [8/8] support fasync feature


related discussion:
--------------------------------------------------------------
 LKML OOM notifications requirement discussion
    http://www.gossamer-threads.com/lists/linux/kernel/832802?nohighlight=1#832802
 OOM notifications patch [Marcelo Tosatti]
    http://marc.info/?l=linux-kernel&m=119273914027743&w=2
 mem notifications v3 [Marcelo Tosatti]
    http://marc.info/?l=linux-mm&m=119852828327044&w=2
 Thrashing notification patch  [Daniel Spang]
    http://marc.info/?l=linux-mm&m=119427416315676&w=2
 mem notification v4
    http://marc.info/?l=linux-mm&m=120035840523718&w=2
 mem notification v5
    http://marc.info/?l=linux-mm&m=120114835421602&w=2

Changelog
-------------------------------------------------
 v5 -> v6 (by KOSAKI Motohiro)
   o rebase to 2.6.24-mm1
   o fixed thundering herd guard formula.

 v4 -> v5 (by KOSAKI Motohiro)
   o rebase to 2.6.24-rc8-mm1
   o change display order of /proc/zoneinfo
   o ignore very small zone
   o support fcntl(F_SETFL, FASYNC)
   o fixed some trivial bugs.

 v3 -> v4 (by KOSAKI Motohiro)
   o rebase to 2.6.24-rc6-mm1
   o avoid wake up all.
   o add judgement point to __free_one_page().
   o add zone awareness.

 v2 -> v3 (by Marcelo Tosatti)
   o changes the notification point to happen whenever
     the VM moves an anonymous page to the inactive list.
   o implement notification rate limit.

 v1(oom notify) -> v2 (by Marcelo Tosatti)
   o name change
   o notify timing change from just swap thrashing to
     just before thrashing.
   o also works with swapless device.
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