[Devel] Re: net namespace plans for 2.6.25 (was Re: Pid namespaces problems)

[Daniel Lezcano]

Denis V. Lunev wrote:
> Daniel Lezcano wrote:
>> Denis V. Lunev wrote:
>>> Daniel Lezcano wrote:
>>>> Denis V. Lunev wrote:
>>>>> Daniel Lezcano wrote:
>>>>>
>>>>>>  * the first one is the locking of the network namespace list by
>>>>>> rtnl_lock, so from the timer callback we can not browse the network
>>>>>> namespace list to check the age of the routes. It is a problem I would
>>>>>> like to talk with Denis if he has time
>>>>> From my point of view, the situation is clear. The timer should be
>>>>> per/namespace. The situation is completely different as one in IPv4.
>>>> We thought to make a timer per namespace for ipv6, but we are a little
>>>> afraid for the performances when there will be a lot of containers.
>>>> Anyway, we can do a timer per namespace and optimize that later. I will
>>>> cook a new patch to take into account that for the next week.
>>> IMHO not a problem. tcp_write_timer is per/socket timer. If this works
>>> efficiently, per/namespace one will work also.
>> That's right, this is a good argument. By the way, the amount of work to
>> be done in the tcp_write_timer is perhaps smaller than the one done in
>> the ipv6 routing age check, no ? Anyway, I'm not against a timer per
>> namespace in this case, I already did a try before rolling back to a
>> for_each_net in the gc timer, that changes a little the API, but nothing
>> we can handle easily.
>>
>>
> I think you are wrong. The amount of work to "purge" all namespaces is a
> constant in the IPv6 case, where we'll have per/namespace cache. So, for
> a multiple timers model only multiple timer overhead counts and this
> overhead is small, as timer list is efficient.
> 
> This argument does not for for IPv4 case, where there is a one big cache
> for all namespaces.

Interesting, thanks for the precision.
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