On Sun, 12 Mar 2000, Rik van Riel wrote:
>You might want to take a look at the process selection
>mechanism in my OOM killer patch (http://www.surriel.com/patches/).
I read the process selection of the oom code in 2.2.15pre12 and it can be
described this way:
"try _not_ to kill tasks that are been started lots of time ago,
that used lots of CPU resources, that are running
non reniced and that are running as roo or with privilegies"
The heuristic has _no-way_ to find out which is the hog. This in turn mean
that you can kill several wrong tasks before you finally kill the right
one and so it's useless and worse than what we have now as far I can tell.
If you hit a feature in a daemon that incidentally causes it to grow at
maximal rate you'll end killing lots of innocents for no good reason.
Your object is defensive "you try not to kill" something that looks more
important.
I instead believe that we should be aggressive against the _hog_ instead
of being defensive against some task that may look as non malicious (but
that you don't know to be innocent).
Once we'll be able to find out which is the hog there will be no need to
look the informations that you are using in your task-selection
algorithm. We know we have to kill the hog, despite of its
euid/priority/lifetime etc...
The idea I had a few weeks ago to solve the problem and so to find out the
hog (and that I'll experiment in real life 2.3.x soon) is to add a
per-task page fault rate (ala avg_slice). Once we'll know the page fault
rate and the time of the last fault per each process, we'll be almost able
to find out the memory hog without possible mistakes and we won't need
anything else.
I completly agree with James (I quote him):
"When you OOM, it's (typically) the case where it's a single process
that's going crazy and being a huge memory hog. Killing other
processes ahead of it won't typically mean very much, as you'll
^^^^^^
have to kill more until you finally get to the
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
spiraling-out-of-control memory hog."
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>> Bottom line is that I don't belive any kind of AI in OMM will do
>> the right job.
>
>So give us a better solution. One that also works for
The task-selection algorithm have nothing to do with AI. It doesn't know
anything about the past and it is not going to learn anything at runtime.
Andrea
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.rutgers.edu
Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Wed Mar 15 2000 - 21:00:23 EST