[Commotion-dev] vm.admin_reserve_kbytes causing OOM crashes

[Dan Staples]

I've been playing around on the new barrier breakers builds of commotion-router, and have been noticing consistent system crashes caused by the kernel's out-of-memory killer when I upload upgrade images through the web interface. It would happen every single time, without exception.

So I compared the OOM settings on the barrier breaker builds versus those on attitude adjustment systems. When I run "sysctl vm", the only significant difference is the addition of the vm.admin_reserve_kbytes=872, which does not exist in on routers running attitude adjustment. According to kernel.org, vm.admin_reserve_kbytes refers to:

"""
The amount of free memory in the system that should be reserved for users
with the capability cap_sys_admin.

admin_reserve_kbytes defaults to min(3% of free pages, 8MB)

That should provide enough for the admin to log in and kill a process,
if necessary, under the default overcommit 'guess' mode.
"""

Thinking this might be the cause of the OOM conditions I was running into, I set admin_reserve_kbytes to 0, and that caused all the OOM-related system crashes to cease.

Has anyone run into this before on BB?

Dan

-- 
Dan Staples

Open Technology Institute
https://commotionwireless.net
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