Messages in this thread | | | Date | Fri, 7 Jul 2006 14:47:25 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH 1/2] srcu-3: RCU variant permitting read-side blocking |
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On Fri, Jul 07, 2006 at 02:11:26PM -0700, Matt Helsley wrote: > On Fri, 2006-07-07 at 15:59 -0400, Alan Stern wrote: > > On Fri, 7 Jul 2006, Paul E. McKenney wrote: > > <snip> > > > > So, a fourth possibility -- can a call from start_kernel() invoke some > > > function in yours and Matt's code invoke init_srcu_struct() to get a > > > statically allocated srcu_struct initialized? Or, if this is part of > > > a module, can the module initialization function do this work? > > > > > > (Hey, I had to ask!) > > > > That is certainly a viable approach: just force everyone to use dynamic > > initialization. Changes to existing code would be relatively few. > > Works for me. I've been working on patches for Andrew's multi-chain > proposal and I could use an init function there anyway. Should be faster > too -- dynamically-allocated per-cpu memory can take advantage of > node-local memory whereas, to my knowledge, statically-allocated cannot.
Sounds very good to me! ;-)
> > I'm not sure where the right place would be to add these initialization > > calls. After kmalloc is working but before the relevant notifier chains > > get used at all. Is there such a place? I guess it depends on which > > notifier chains we convert. > > > > We might want to leave some chains using the existing rw-semaphore API. > > It's more appropriate when there's a high frequency of write-locking > > (i.e., things registering or unregistering on the notifier chain). The > > SRCU approach is more appropriate when the chain is called a lot and > > needs to have low overhead, but (un)registration is uncommon. Matt's task > > notifiers are a good example. > > Yes, it is an excellent example.
Good!!! Please let me know how it goes. I will shelve the idea of statically allocated per-CPU data for srcu_struct for the moment. If some other application shows up that needs it, I will revisit.
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