On 04.08.2020 16:52, Eric W. Biederman wrote: > Kirill Tkhai <ktk...@virtuozzo.com> writes: > >> On 04.08.2020 15:21, Eric W. Biederman wrote: >>> Kirill Tkhai <ktk...@virtuozzo.com> writes: >>> >>>> Currently, every type of namespaces has its own counter, >>>> which is stored in ns-specific part. Say, @net has >>>> struct net::count, @pid has struct pid_namespace::kref, etc. >>>> >>>> This patchset introduces unified counter for all types >>>> of namespaces, and converts net namespace to use it first. >>> >>> And the other refcounts on struct net? >>> >>> How do they play into what you are trying to do? >> >> I just don't understand you. Different refcounters are related to different >> problems, they are introduced to solve. This patchset changes only one >> refcounter, >> and it does not touch other of them. What do you want to know about others? >> > > Why net::count not net::passive? What problem are you trying to solve?
net::count is a counter, which indicates whether net is alive and still initilized. net::passive does not guarantees that net has not been deinitialized yet. The same with another namespaces. All of merged counters indicate that a namespace is alive and initialized. So, we merge them by this property. > They both are reference counts on the network namespace. > > I don't understand what you are trying to do, other than take a bunch of > things that look similar and squash them all together. > > What semantics does this magical common reference count have? > Why is it better for the count to live in ns_common rather than it > it's own dedicated field of struct net? The only visible current effect is better readability and better debugability with, say, crash on kernel dump. > Given that decrementing still requires code per namespace to handle > the count going to zero. How does this benefit anyone? Since namespaces are different by type, they require different destructors. Generic counter can't solve any problem, the namespaces can address. > Has the effect of cache line placement of the move of the reference > count been considered? I don't see any performance impact during namespace creation/destruction test. > All I see in the patch in question is switching a location that the > count lives. Which does not seem useful to me. > > I am not fundamentally oppossed but I don't see the point. At this > point it looks like you are making things harder to maintain by making > things common that are merely similar
