Re: [dpdk-dev] [PATCH v2 2/2] eal: roundup tsc frequency when estimating it

["Wiles, Keith" <keith.wiles@intel.com>]

> On Mar 16, 2019, at 2:03 AM, Pavan Nikhilesh Bhagavatula <pbhagavatula@marvell.com> wrote:
> 
> From: Pavan Nikhilesh <pbhagavatula@marvell.com>
> 
> When estimating tsc frequency using sleep/gettime round it up to the
> nearest multiple of 10Mhz for more accuracy.
> 
> Signed-off-by: Pavan Nikhilesh <pbhagavatula@marvell.com>
> ---
> Useful in case of ARM64 if we enable RTE_ARM_EAL_RDTSC_USE_PMU,
> get_tsc_freq_arch() will return 0 as there is no instruction to determine
> the clk of PMU and eal falls back to sleep(1).
> 
> lib/librte_eal/common/eal_common_timer.c | 4 ++--
> lib/librte_eal/linuxapp/eal/eal_timer.c  | 2 +-
> 2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/librte_eal/common/eal_common_timer.c b/lib/librte_eal/common/eal_common_timer.c
> index dcf26bfea..1358bbed0 100644
> --- a/lib/librte_eal/common/eal_common_timer.c
> +++ b/lib/librte_eal/common/eal_common_timer.c
> @@ -69,7 +69,7 @@ estimate_tsc_freq(void)
> 	/* assume that the sleep(1) will sleep for 1 second */
> 	uint64_t start = rte_rdtsc();
> 	sleep(1);
> -	return rte_rdtsc() - start;
> +	return RTE_ALIGN_MUL_NEAR(rte_rdtsc() - start, 1E7);
> }
> 
> void
> @@ -83,7 +83,7 @@ set_tsc_freq(void)
> 	if (!freq)
> 		freq = estimate_tsc_freq();
> 
> -	RTE_LOG(DEBUG, EAL, "TSC frequency is ~%" PRIu64 " KHz\n", freq / 1000);
> +	RTE_LOG(INFO, EAL, "TSC frequency is ~%" PRIu64 " Hz\n", freq);
> 	eal_tsc_resolution_hz = freq;
> }
> 
> diff --git a/lib/librte_eal/linuxapp/eal/eal_timer.c b/lib/librte_eal/linuxapp/eal/eal_timer.c
> index bc8f05199..864d6ef29 100644
> --- a/lib/librte_eal/linuxapp/eal/eal_timer.c
> +++ b/lib/librte_eal/linuxapp/eal/eal_timer.c
> @@ -248,7 +248,7 @@ get_tsc_freq(void)
> 
> 		double secs = (double)ns/NS_PER_SEC;
> 		tsc_hz = (uint64_t)((end - start)/secs);
> -		return tsc_hz;
> +		return RTE_ALIGN_MUL_NEAR(tsc_hz, 1E7);

Maybe I missed an email about this, but why would I want the TSC hz rounded here? I do not mind the macro just the fact that we are changing TSC hz value. If the TSC value is wrong then we need to fix the value, but I do not see it being wrong here.
> 	}
> #endif
> 	return 0;
> --
> 2.21.0
> 

Regards,
Keith