linux-kernel - Re: additional oom-killer tuneable worth submitting?

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Message-ID: <457886B4.2030507@nortel.com>
Date:	Thu, 07 Dec 2006 15:25:08 -0600
From:	"Chris Friesen" <cfriesen@...tel.com>
To:	Jesper Juhl <jesper.juhl@...il.com>
CC:	linux-kernel@...r.kernel.org
Subject: Re: additional oom-killer tuneable worth submitting?

Jesper Juhl wrote:

> How does "oomthresh" and "oomadj" affect each other?

If memory consumption is less than "oomthresh", that process is simply 
bypassed.  (Equivalent to oomkilladj==OOM_DISABLE.)  Otherwise, continue 
processing as normal.

> Default "oomthresh" value for a new process is 0 (zero) I assume -
> right?  If not, then I'd suggest that it should be.

Correct.

> What happens when a process fork()s? Does the child enherit the
> parents "oomthresh" value?

Currently it does not.  This is to allow for different memory access 
patterns by parent/child.  And exec() wipes it as well.

> Would it make sense to make "oomthresh" apply to process groups
> instead of processes?

Hmm...it might make sense given that the point of the group is to manage 
tasks together...but it would make accounting more tricky.  Currently 
it's just a very simple comparison of p->mm->total_vm against the 
threshold in badness().

> What happens in the case where the OOM killer really, really needs to
> kill one or more processes since there is not a single drop of memory
> available, but all processes are below their configured thresholds?

Then the system wasn't properly engineered.  <grin>

In this case you reboot.

Chris
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