Re: [PATCH v4 0/4] cgroup notifications API and memory thresholds

[Kirill A. Shutemov]

On Sun, Dec 27, 2009 at 2:47 PM, Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx> wrote:
> * Kirill A. Shutemov <kirill@xxxxxxxxxxxxx> [2009-12-27 04:08:58]:
>
>> This patchset introduces eventfd-based API for notifications in cgroups and
>> implements memory notifications on top of it.
>>
>> It uses statistics in memory controler to track memory usage.
>>
>> Output of time(1) on building kernel on tmpfs:
>>
>> Root cgroup before changes:
>> Â Â Â make -j2 Â506.37 user 60.93s system 193% cpu 4:52.77 total
>> Non-root cgroup before changes:
>> Â Â Â make -j2 Â507.14 user 62.66s system 193% cpu 4:54.74 total
>> Root cgroup after changes (0 thresholds):
>> Â Â Â make -j2 Â507.13 user 62.20s system 193% cpu 4:53.55 total
>> Non-root cgroup after changes (0 thresholds):
>> Â Â Â make -j2 Â507.70 user 64.20s system 193% cpu 4:55.70 total
>> Root cgroup after changes (1 thresholds, never crossed):
>> Â Â Â make -j2 Â506.97 user 62.20s system 193% cpu 4:53.90 total
>> Non-root cgroup after changes (1 thresholds, never crossed):
>> Â Â Â make -j2 Â507.55 user 64.08s system 193% cpu 4:55.63 total
>>
>> Any comments?
>
> Thanks for adding the documentation, now on to more critical questions
>
> 1. Any reasons for not using cgroupstats?

Could you explain the idea? I don't see how cgroupstats applicable for
the task.

> 2. Is there a user space test application to test this code.

Attached. It's not very clean, but good enough for testing propose.
Example of usage:

$ echo '/cgroups/memory.usage_in_bytes 1G' | ./cgroup_event_monitor

> ÂIIUC,
> I need to write a program that uses eventfd(2) and then passes
> the eventfd descriptor and thresold to cgroup.*event* file and
> then the program will get notified when the threshold is reached?

You need to pass eventfd descriptor, descriptor of control file to be
monitored (memory.usage_in_bytes or memory.memsw.usage_in_bytes) and
threshold.

Do you want to rename cgroup.event_control to cgroup.event?

Attachment: cgroup_event_monitor.c
Description: Binary data