On Mon, 15 Apr 2019 17:39:07 +0000 "Ananyev, Konstantin" <[email protected]> wrote:
> > -----Original Message----- > > From: Stephen Hemminger [mailto:[email protected]] > > Sent: Monday, April 15, 2019 4:39 PM > > To: Ananyev, Konstantin <[email protected]> > > Cc: Honnappa Nagarahalli <[email protected]>; > > [email protected]; Kovacevic, Marko > > <[email protected]>; [email protected]; Gavin Hu (Arm Technology China) > > <[email protected]>; Dharmik Thakkar > > <[email protected]>; Malvika Gupta <[email protected]>; nd > > <[email protected]> > > Subject: Re: [PATCH v5 1/3] rcu: add RCU library supporting QSBR mechanism > > > > On Mon, 15 Apr 2019 12:24:47 +0000 > > "Ananyev, Konstantin" <[email protected]> wrote: > > > > > > -----Original Message----- > > > > From: Stephen Hemminger [mailto:[email protected]] > > > > Sent: Saturday, April 13, 2019 12:06 AM > > > > To: Honnappa Nagarahalli <[email protected]> > > > > Cc: Ananyev, Konstantin <[email protected]>; > > > > [email protected]; Kovacevic, Marko <[email protected]>; > > > > [email protected]; Gavin Hu (Arm Technology China) <[email protected]>; > > > > Dharmik Thakkar <[email protected]>; Malvika > > Gupta > > > > <[email protected]>; nd <[email protected]> > > > > Subject: Re: [PATCH v5 1/3] rcu: add RCU library supporting QSBR > > > > mechanism > > > > > > > > On Fri, 12 Apr 2019 22:24:45 +0000 > > > > Honnappa Nagarahalli <[email protected]> wrote: > > > > > > > > > > > > > > > > On Fri, 12 Apr 2019 15:20:37 -0500 > > > > > > Honnappa Nagarahalli <[email protected]> wrote: > > > > > > > > > > > > > Add RCU library supporting quiescent state based memory > > > > > > > reclamation > > > > > > method. > > > > > > > This library helps identify the quiescent state of the reader > > > > > > > threads > > > > > > > so that the writers can free the memory associated with the lock > > > > > > > less > > > > > > > data structures. > > > > > > > > > > > > > > Signed-off-by: Honnappa Nagarahalli <[email protected]> > > > > > > > Reviewed-by: Steve Capper <[email protected]> > > > > > > > Reviewed-by: Gavin Hu <[email protected]> > > > > > > > Reviewed-by: Ola Liljedahl <[email protected]> > > > > > > > Acked-by: Konstantin Ananyev <[email protected]> > > > > > > > > > > > > After evaluating long term API/ABI issues, I think you need to get > > > > > > rid of almost > > > > > > all use of inline and visible structures. Yes it might be > > > > > > marginally slower, but > > > > > > you thank me the first time you have to fix something. > > > > > > > > > > > Agree, I was planning on another version to address this (I am yet to > > > > > take a look at your patch addressing the ABI). > > > > > The structure visibility definitely needs to be addressed. > > > > > For the inline functions, is the plan to convert all the inline > > > > > functions in DPDK? If yes, I think we need to consider the > > > > > performance > > > > difference. May be consider L3-fwd application, change all the inline > > > > functions in its path and run a test? > > > > > > > > Every function that is not in the direct datapath should not be inline. > > > > Exceptions or things like rx/tx burst, ring enqueue/dequeue, and packet > > > > alloc/free > > > > > > Plus synchronization routines: spin/rwlock/barrier, etc. > > > I think rcu should be one of such exceptions - it is just another > > > synchronization mechanism after all > > > (just a bit more sophisticated). > > > Konstantin > > > > If you look at the other userspace RCU, you wil see that the only inlines > > are the rcu_read_lock,rcu_read_unlock and rcu_reference/rcu_assign_pointer. > > > > The synchronization logic is all real functions. > > In fact, I think urcu provides both flavors: > https://github.com/urcu/userspace-rcu/blob/master/include/urcu/static/urcu-qsbr.h > I still don't understand why we have to treat it differently then let say > spin-lock/ticket-lock or rwlock. > If we gone all the way to create our own version of rcu, we probably want it > to be as fast as possible > (I know that main speedup should come from the fact that readers don't have > to wait for writer to finish, but still...) > > Konstantin > Having locking functions inline is already a problem in current releases. The implementation can not be improved without breaking ABI (or doing special workarounds like lock v2)
