Re: [RFC] [PATCH] cgroup: limit network bandwidth

[Andrea Righi]

Balbir Singh wrote:
> * Andrea Righi <righiandr@xxxxxxxxxxxxxxxxxxxxx> [2008-01-23 10:09:28]:
> 
>> Allow to limit the network bandwidth for specific process containers (cgroups)
>> imposing additional delays in the sockets' sendmsg()/recvmsg() calls made by
>> those processes that exceed the limits defined in the control group filesystem.
>>
>> Example:
>>   # mkdir /dev/cgroup
>>   # mount -t cgroup -onet net /dev/cgroup
>>   # cd /dev/cgroup
>>   # mkdir foo
>>   --> the cgroup foo has been created
>>   # /bin/echo $$ > foo/tasks
>>   # /bin/echo 1024 > foo/net.tcp
>>   # /bin/echo 2048 > foo/net.tot
>>   # sh
>>   --> the subshell 'sh' is running in cgroup "foo" that has a maximum network
>>       bandwidth for TCP traffic of 1MB/s and 2MB/s for total network
>>       activities.
>>
>> The netlimit approach can be easily extended to support additional network
>> protocols or different socket families or types (PF_UNIX, PF_BLUETOOTH,
>> SOCK_SEQPACKET, etc.).
>>
>> Signed-off-by: Andrea Righi <a.righi@xxxxxxxxx>
> 
> Hi, Andrea,
> 
> I took a quick look at the patches and it looks like we throttle
> network (by forcing a schedule_timeout()), if we exceed our bandwidth
> limit. That is one way of doing it, but it has some disadvantages, it
> does not scale to 
> 
> 1. Implementation of soft limits (limit on contention of resource)
>    gets harder

Why? do you mean implementing a grace time when the soft-limit is
exceeded? this could be done in cgroup_nl_throttle() introducing 3 
additional attributes to struct netlimit (i.e. hard_limit,
last_time_exceeded grace_time) and perform something like:
...
	if ((current_rate > hard_limit) ||
	    time_after(jiffies, last_time_exceeded + grace_time))
			schedule_timeout(sleep);
...

> 2. Why dont use the existing infrastructure for bandwidth limitation
>    for implementing the network controller?
> 

Yes, the integration with iptables (as Paul said), and traffic shaping
rules would be absolutely the right way(tm) in perspective. I was just
proposing a possible simple API to implement the limiting stuff.

-Andrea
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