Messages in this thread | | | Date | Fri, 19 Oct 2007 00:01:26 +0200 | From | Rene Herman <> | Subject | Re: OOM notifications |
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On 10/18/2007 11:18 PM, Rik van Riel wrote:
> On Thu, 18 Oct 2007 23:06:52 +0200 > Rene Herman <rene.herman@keyaccess.nl> wrote: > >> 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? > > The first threshold - "we are about to swap" - means the application > frees memory that it can. Eg. free()d memory that glibc has not yet > given back to the kernel, or JVM running the garbage collector, or ... > > The second threshold - "we are out of memory" - means that the first > approach has failed and the system needs to do something else. On an > embedded system, I would expect some application to exit or maybe > restart itself.
That first threshold sounds fine yes. To me, the second mostly sounds like a job for SIGTERM though.
The OOM killer could after it selected the task for killing first try a TERM on it to give a chance to exit gracefully and only when that doesn't help make it eligible for killing on a second round through the badness calculation.
You could moreover _never_ make a task eligible for killing before it received a SIGTERM, thereby guaranteeing that everyone got the SIGTERM before killing anything, and it seems SIGTERM would be a more focussed version of SIGDANGER2 then.
Would at least forego any need for multiplexing the DANGER signal.
Rene.
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