OOM killer "Out of Memory: Killed process" SOLUTIONS / SUMMARY

[Eric Sisler]

Hi Manuel,

> The fact of having large amounts of memory is important? I mean, this
> can happen either with 2GB or 10GB?

Yes.  More total RAM = more low memory required to map high memory
usage.  This problem never occurred here on older servers with 6Gb or
RAM or less, even on those with many virtual machines running.  The
first time it happened here was on a server with 8Gb RAM.

> It´s just curiosity, I have never ever faced this problem. I found
> this topic really interesting, though

"Interesting" is only one of the words I used while trying to solve the
problem... <grin>

> Does hugemen act as a module or...? How can it expand the low memory?

It's a different kernel that splits low & high memory differently.  On a
server with 8Gb RAM:

Kernel    HighTotal    LowTotal     MemTotal
----------------------------------------------
regular   7470840 kB    837724 kB   8308564 kB
hugemem   5242872 kB   3063376 kB   8306248 kB

Notice that low memory took a significant jump when running the hugemem
kernel, at the expense of high memory.  Total memory is also a bit
smaller, probably due to overhead imposed by the hugemem kernel.

> If the first solution, your point was to upgrade to 64-bit. And as you
> wrote, if you even run out of low memory...pray.
> What if you do the vm.lower_zone_protection = 250 ? Should it give you
> some more "extra time" before the disaster?

There really isn't any need for lower_zone_protection when using the 64-
bit kernel as *all* memory is lower memory.  Same 8Gb server with the
64-bit kernel running:

HighTotal:           0 kB
LowTotal:      8162488 kB
MemTotal:      8162488 kB

> Really interesting post, Eric.

Glad you found it interesting.

> Eventually, what did you do? Upgrade? Disable oom-killer? Pray? Delete
> VMWare server? :-)

1) Upgrade to 64-bit for newer servers.
2) Run the hugemem kernel on older servers with 6Gb or more of RAM.

No further problems encountered.  :-)

-Eric

-- 
Eric Sisler <esisler at westminster.lib.co.us>
Library Network Specialist
Westminster Public Library
Westminster, CO USA

Linux - Don't fear the Penguin.
Want to know what we use Linux for?
Visit http://wallace.westminster.lib.co.us/linux