BUG: oom-killer active when overcommit_memory contains '2', and more...

From: Jeff Blaine
Date: Thu Jan 20 2005 - 08:54:50 EST


I see this as 2 bugs, personally, and will say right up front
that none of these problems exist in 2.4.10. I don't mean
to sound flippant, but also have to say that the reality of
this is that I do not have the time to test things further
for anyone. Filing this bug report is as much as I have time
for (in addition to all of the time I have spent on this
already before this message).

1. Filling up the memory on a 2.6.10 box renders it completely
and permanently useless even after the memory-filling process
exits due to oom-killer's havoc.

I came across this problem when running Iozone NFSv3
benchmarks. The client Linux box in question is running
2.6.10 (Fedora Core 3 with latest updates) and has 4GB
physical memory and 4GB in a swap partition. To perform
a proper Iozone benchmark for NFS testing, one needs to
specify a test file size that is larger than the amount
of memory in the client. In my case, 4224MB is being
specified:

./iozone -a -g 4224m -f /sol9server/testfile

As soon as it finally gets to trying a file size of
4194304, oom-killer steps in and starts blasting
processes off my machine. NFS stops functioning,
RPC calls to the box fail, SSH connections are no
longer accepted, and I generally have to hard
powercycle the box. That's pretty poor :)

2. Andries Brouwer looked into this and asked me to try
turning off oom-killer with the following command:

echo 2 > /proc/sys/vm/overcommit_memory

Re-running the 4GB benchmark with Iozone, this did
nothing and oom-killer walked through the door blasting
processes off of my machine, rendering it totally
broken in the end.

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