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From: Jerin Jacob <jerin.jacob@caviumnetworks.com>
Subject: Re: [PATCH] eal/armv8: high-resolution cycle counter
Date: Fri, 19 Aug 2016 18:22:18 +0530
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Cc: Nipun Gupta <nipun.gupta@nxp.com>, "dev@dpdk.org" <dev@dpdk.org>,
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To: Jan Viktorin <viktorin@rehivetech.com>
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On Fri, Aug 19, 2016 at 02:24:58PM +0200, Jan Viktorin wrote:
> On Fri, 19 Aug 2016 17:16:12 +0530
> Jerin Jacob <jerin.jacob@caviumnetworks.com> wrote:
> 
> 
> I've got a private kernel driver enabling and disabling (hopefully) properly
> this for ARMv7. If we'd like to merge it, I'd like to have a single module
> or at least single module with 2 implementations...
> 
> I can post it if it would be helpful.

I don't think we can use this in production as this may alter PMU state used
by 'perf' etc.I think let it be a debug interface for armv7 and armv8
and disable it by default.


> 
> Regards
> Jan
> 
> > 
> > >   
> > > > + *
> > > > + */
> > > > +static inline uint64_t
> > > > +rte_rdtsc(void)
> > > > +{
> > > > +	uint64_t tsc;
> > > > +
> > > > +	asm volatile("mrs %0, pmccntr_el0" : "=r"(tsc));
> > > > +	return tsc;
> > > > +}
> > > > +#endif
> > > > 
> > > >  static inline uint64_t
> > > >  rte_rdtsc_precise(void)
> > > > --
> > > > 2.5.5  
> > > 
> > > Do you also plan to support performance monitor event counters?  
> > 
> > No. This patch was inspired by armv7 PMU scheme and its part of DPDK.
> > The sole reason to add this support to catch any performance regression
> > through app/test application.Other than that, I think cntvct_el0 based
> > existing scheme is good enough for all the use cases.
> > 
> > > 
> > > Regards,
> > > Nipun
> > >   
> 
> 
> 
> -- 
>    Jan Viktorin                  E-mail: Viktorin@RehiveTech.com
>    System Architect              Web:    www.RehiveTech.com
>    RehiveTech
>    Brno, Czech Republic