Implement registering for other memory notifications besides oom

[dcantah]

• Implement functionality to register for events on the other memory cgroup files
  that support the notification API (memory.usage_in_bytes, memory.memsw.usage_in_bytes,
  memory.pressure_limit).

• Small typo fix in hierarchy.go. enableds -> enables

Signed-off-by: Daniel Canter dcanter@microsoft.com

[crosbymichael]

What do you think about a single method that can return uintptr, error but handle args and the type of event that you would like to receive? Just thinking so we could keep the interface small and support these and any other events from the subsystems in the future.

[dcantah]

@crosbymichael I agree this would be better but I didn't know if you guys wanted to keep OOMEventFD as part of the interface so I simply added the new events to it as well. In your proposal we would be getting rid of OOMEventFD and the two new ones in favor of just one method (let's call it MemoryEvent or similar) if I'm understanding correctly?

[crosbymichael]

I think we would need to keep OOMEventFD for a little bit to give ppl time to move over to the new method.

MemoryEvent sounds good to me.

[dcantah]

@crosbymichael Cool I'll get to work

[crosbymichael]

thanks!

[dcantah]

@crosbymichael PTAL

[crosbymichael]

LGTM