Re: OOM notifications
From: Rene Herman
Date: Thu Oct 18 2007 - 17:09:31 EST
On 10/18/2007 10:52 PM, Rik van Riel wrote:
On Thu, 18 Oct 2007 22:38:21 +0200
Rene Herman <rene.herman@xxxxxxxxxxxx> wrote:
On 10/18/2007 10:25 PM, Marcelo Tosatti wrote:
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.
Given the desktop/embedded distinction you made, do you need both
scenarios active at the same time? If not, it seems something like a
echo -n <level> >/proc/sys/vm/danger
could do with just one sigdanger notification point? (with <level>
suitably defined as or in terms of the used threshold value).
If you do that, how are applications to know which of the two
scenarios is happening when they get a signal?
They don't -- that's why I asked if you need both scenario's active at the
same time. SIGDANGER would just be SIGPLEASEFREEALLYOUCAN with the operator
deciding through setting the level at which point applications get it.
Or put differently; what's the additional value of notifying an application
that the system is about to go balistic when you've already asked it to free
all it could earlier? SIGSEEDAMNITITOLDYOUSO?
Don't get me wrong; never saw this discussion earlier, may be sensible...
Rene.
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