[Devel] NFSd threads amount policy in containers context

[Stanislav Kinsbursky]

27.11.2012 02:08, bfields at fieldses.org пишет:
> On Mon, Nov 26, 2012 at 08:09:01PM +0400, Stanislav Kinsbursky wrote:
>> Hello.
>> I would like to discuss how to control NFSd threads amount from
>> container environment (is this particular case it means start of NFS
>> server in network namespace different to init_net).
>>
>> So, I see three possible policies (let's assume, that there are two containers - one requested 3 NFSd threads and another one - 4 NFSd threads):
>> 1) start as many threads, as requested. I.e 7 threads for specified
>> case (simplest case, but probably this is to much - 100 containers
>> will start ~800 threads by default).
>> 2) start maximum number of requested threads. I.e. 4 threads for
>> specified case (if NFSd server in container, requested 4 threads,
>> will be stopped, then 3 thread will left working; will require some
>> way to manage - rb tree of sorted list).
>> 3) There could be some other (more flexible) policy: combine second
>> one with running of one more thread for each second and further
>> network namespace, started NFS server. I.e.:
>> 1 net ns: 3 threads request = 3 threads started
>> 2 net ns: 4 threads request = 4 + 1 (per-net thread: 1 net ns) = 5 threads started
>> 3 net ns: 8 threads request = 8 + 2 (per-net threads: 2 net ns) = 10 threads started
>>
>> Bruce and community, what do you think about all this?
>
> I agree that options 2 or 3 seem more likely to be optimal.
>
> However, looking at the problems with, for example, getting race-free
> shutdown correct: I'd *strongly* prefer that we start with 1, because I
> think it will be simplest to get right.
>
> I'd rather put off figuring out how to scale to hundreds of containers
> until after we demonstrate something simple and obviously correct.
>

Ok. Then I think we could implement even a better and simpler solution:
make the whole nfsd_serv per network namespace.
This solution is easy to implement, non-racy on shutdown and will give us a rather easy way to apply scheduler policy to NFSd threads (this will be most 
probably required in future).
Does it sounds good to you?



-- 
Best regards,
Stanislav Kinsbursky