> On Thu, 18 Oct 2007 16:15:31 -0400
> Marcelo Tosatti <marcelo@kvack.org> wrote:
>
>> Hi,
>>
>> AIX contains the SIGDANGER signal to notify applications to free up some
>> unused cached memory:
>>
>>
http://www.ussg.iu.edu/hypermail/linux/kernel/0007.0/0901.html
>>
>> There have been a few discussions on implementing such an idea on Linux,
>> but nothing concrete has been achieved.
>>
>> On the kernel side Rik suggested two notification points: "about to
>> swap" (for desktop scenarios) and "about to OOM" (for embedded-like
>> scenarios).
>>
>> With that assumption in mind it would be necessary to either have two
>> special devices for notification, or somehow indicate both events
>> through the same file descriptor.
>>
>> Comments are more than welcome.
>
> Martin was talking about some mad scheme wherin you'd create a bunch of
> pseudo files (say, /proc/foo/0, /proc/foo/1, ..., /proc/foo/9) and each one
> would become "ready" when the MM scanning priority reaches 10%, 20%, ...
> 100%.
>
> Obviously there would need to be a lot of abstraction to unhook a permanent
> userspace feature from a transient kernel implementation, but the basic
> idea is that a process which wants to know when the VM is getting into the
> orange zone would select() on the file "7" and a process which wants to
> know when the VM is getting into the red zone would select on file "9".
>
> It get more complicated with NUMA memory nodes and cgroup memory
> controllers.
