Re: the new VM

[Christoph Rohland <cr@sap.com>]

Rik van Riel <riel@conectiva.com.br> writes:

> Hmmm, could you help me with drawing up a selection algorithm
> on how to choose which SHM segment to destroy when we run OOM?
> 
> The criteria would be about the same as with normal programs:
> 
> 1) minimise the amount of work lost
> 2) try to protect 'innocent' stuff
> 3) try to kill only one thing
> 4) don't surprise the user, but chose something that
>    the user will expect to be killed/destroyed

First we only kill segments with no attachees. There are circumstances
under normal load where you have these. (SAP R/3 will do this all the
time on Linux 2.4) 

So perhaps we could signal shm that we killed a process and let it try
to find a segment where this process was the last attachee. This would
be a good candidate.

If this does not help either we could do two different things:
1) kill the biggest nonattached segment
2) kill the segment which was longest detached

Greetings
		Christoph

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