Messages in this thread | | | Date | Wed, 28 Jul 2021 14:39:34 -0400 (EDT) | From | Mathieu Desnoyers <> | Subject | Re: [PATCH v2 rcu 04/18] rcu: Weaken ->dynticks accesses and updates |
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----- On Jul 28, 2021, at 2:32 PM, Linus Torvalds torvalds@linux-foundation.org wrote:
> On Wed, Jul 28, 2021 at 11:12 AM Mathieu Desnoyers > <mathieu.desnoyers@efficios.com> wrote: >> >> Are the percpu atomics you have in mind different from what is found in >> Documentation/core-api/this_cpu_ops.rst ? >> >> Namely this_cpu_add_return(pcp, val) in this case. > > Nope. > > Those are only "CPU-atomic", ie atomic wrt interrupts etc. > > The RCU code wants SMP-atomic, and it's mainly that we *could* do the > addressing more efficiently.
OK, so combining the addressing tricks of this_cpu operations with smp-atomic operations (e.g. LOCK prefix on x86). It may indeed become worthwhile given enough users, and fast enough atomic operations.
Thanks,
Mathieu
-- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com
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