Yo,

Interesting patch series (I am being yuppie and reading this thread  
from my iPhone on a treadmill at the gym - so further comments later).  
I think that this is broadly along the lines that I was thinking, but  
this should be an RFC only patch series for now.

Some initial questions:

Where is the netlink interface? Polling an FD is so last century :)

What testing have you done?

Still, it is good to start with some code - eventually we might just  
have a full reservation API created. Rik and I and others have bounced  
ideas around for a while and I hope we can pitch in. I will play with  
these patches later.

Jon.



On Feb 9, 2008, at 10:19, "KOSAKI Motohiro" <kosaki.motohiro@jp.fujitsu.com 
 > wrote:

quoted text
> 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 fre 
> e.
> 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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