Messages in this thread | | | Date | Thu, 7 Nov 2019 12:36:53 -0500 | From | Dennis Zhou <> | Subject | Re: [PATCH] percpu-refcount: Use normal instead of RCU-sched" |
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On Thu, Nov 07, 2019 at 06:24:34PM +0100, Sebastian Andrzej Siewior wrote: > On 2019-11-07 11:55:19 [-0500], Dennis Zhou wrote: > > On Thu, Nov 07, 2019 at 05:28:42PM +0100, Sebastian Andrzej Siewior wrote: > > > > I just want to clarify a little bit. Is this patch aimed at fixing an > > > > issue with RT kernels specifically? > > > > > > Due to the implications of preempt_disable() on RT kernels it fixes > > > problems with RT kernels. > > > > > > > Great, do you mind adding this explanation with what the implications > > are in the commit message? > > some RCU section here invoke callbacks which acquire spinlock_t locks. > This does not work on RT with disabled preemption. >
Yeah, so adding a bit in the commit message about why it's an issue for RT kernels with disabled preemption as I don't believe this is an issue for non-RT kernels.
> > > > It'd also be nice to have the > > > > numbers as well as if the kernel was RT or non-RT. > > > > > > The benchmark was done on a CONFIG_PREEMPT kernel. As said in the commit > > > log, the numbers were mostly the same, I can re-run the test and post > > > numbers if you want them. > > > This patch makes no difference on PREEMPT_NONE or PREEMPT_VOLUNTARY > > > kernels. > > > > > > > I think a more explicit explanation in the commit message would suffice. > > What do you mean by "more explicit explanation"? The part with the > numbers or that it makes no difference for PREEMPT_NONE and > PREEMPT_VOLUNTARY? >
I just meant the above, the benchmarking is fine.
Thanks, Dennis
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