Messages in this thread | | | Date | Wed, 2 Sep 2020 15:48:05 +0200 | From | peterz@infradea ... | Subject | Re: [PATCH v3 2/6] perf tsc: Add rdtsc() for Arm64 |
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On Wed, Sep 02, 2020 at 02:21:27PM +0100, Leo Yan wrote: > The system register CNTVCT_EL0 can be used to retrieve the counter from > user space. Add rdtsc() for Arm64.
> +u64 rdtsc(void) > +{ > + u64 val;
Would it make sense to put a comment in that this counter is/could-be 'short' ? Because unlike x86-TSC, this thing isn't architecturally specified to be 64bits wide.
> + asm volatile("mrs %0, cntvct_el0" : "=r" (val)); > + > + return val; > +} > -- > 2.17.1 >
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