Re: [PATCH RFC v2 rcu 1/8] srcu: Convert ->srcu_lock_count and ->srcu_unlock_count to atomic

[John Ogness]

On 2022-09-30, "Paul E. McKenney" <paulmck@xxxxxxxxxx> wrote:
>> > -	this_cpu_inc(ssp->sda->srcu_lock_count[idx]);
>> > +	this_cpu_inc(ssp->sda->srcu_lock_count[idx].counter);
>> 
>> Is there any particular reason that you are directly modifying
>> @counter instead of raw_cpu_ptr()+atomic_long_inc() that do you in
>> __srcu_read_lock_nmisafe() of patch 2?
>
> Performance.  From what I can see, this_cpu_inc() is way faster than
> atomic_long_inc() on x86 and s390.  Maybe also on loongarch.  No idea
> on arm64.

Yeah, that's what I figured. I just wanted to make sure.

FWIW, the rest of the series looks pretty straight forward to me.

John