cgroup memory limit problems

["Arkadiusz Miśkiewicz" <arekm-evZBlRFTdvA@public.gmane.org>]

Hi,

I have a machine with 6GB of ram and a cgroup for apache processes limited to 
                memory.limit_in_bytes = "5100M";
                memory.soft_limit_in_bytes = "5000M";

Unfortunately when apache processes ate all ram assigned to their cgroup load 
on whole machine jumps the roof.

cgroup aware OOM kicks in, kills one process and that doesn't help.

If I'm fast enough I notice and then apache processes require tons of kill -9 
(I'm doing "killall -9 apache" in a while (true) loop for 20-30s) to get 
killed (and that not always succeeds - sometimes I'm unable to kill these and 
I'm just doing sysrq u, s, b after few minutes.. if I'm lucky. Sometimes I 
cannot do any command).

This all happens on 2.6.38.8 kernel.
http://ixion.pld-linux.org/~arekm/cgroup-eaten-memory-failure-1.txt
for kernel log. It ends with reboot of the machine.

Now the question is - is this is how cgroup memory limit supposed to work? If 
yes then it's hardly usable but maybe there are some patches for this?

Would newer kernels be better ? (cannot test immediately since newer kernels 
kill ipmi connectivity on that machine). I would expect apache processes to be 
killed without taking down entire machine.

ps. found similar history at http://serverfault.com/questions/211509/how-to-
stop-apache-from-crashing-my-entire-server from year ago
-- 
Arkadiusz Miśkiewicz        PLD/Linux Team
arekm / maven.pl            http://ftp.pld-linux.org/
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