Re: [dpdk-dev] [PATCH 2/5] app/testpmd: print fractional part in CPU cycles

["Ananyev, Konstantin" <konstantin.ananyev@intel.com>]

> Hi Konstantin,
> 
> > On May 7, 2020, at 4:50 AM, Ananyev, Konstantin <konstantin.ananyev@intel.com> wrote:
> >
> >
> >
> >> -----Original Message-----
> >> From: dev <dev-bounces@dpdk.org> On Behalf Of Dharmik Thakkar
> >> Sent: Wednesday, May 6, 2020 10:59 PM
> >> To: Lu, Wenzhuo <wenzhuo.lu@intel.com>; Wu, Jingjing <jingjing.wu@intel.com>; Iremonger, Bernard <bernard.iremonger@intel.com>
> >> Cc: dev@dpdk.org; nd@arm.com; Dharmik Thakkar <dharmik.thakkar@arm.com>
> >> Subject: [dpdk-dev] [PATCH 2/5] app/testpmd: print fractional part in CPU cycles
> >>
> >> Change printing of CPU cycles/packet to include fractional part for
> >> accurateness.
> >>
> >> Example:
> >>
> >> Without patch:
> >> CPU cycles/packet=14
> >> (total cycles=4899533541 / total RX packets=343031966)
> >>
> >> With patch:
> >> CPU cycles/packet=14.28
> >> (total cycles=4899533541 / total RX packets=343031966)
> >>
> >> Signed-off-by: Dharmik Thakkar <dharmik.thakkar@arm.com>
> >> Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> >> Reviewed-by: Phil Yang <phil.yang@arm.com>
> >> ---
> >> app/test-pmd/testpmd.c | 4 ++--
> >> 1 file changed, 2 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/app/test-pmd/testpmd.c b/app/test-pmd/testpmd.c
> >> index 9a8cbbd6fc7c..9444a730a153 100644
> >> --- a/app/test-pmd/testpmd.c
> >> +++ b/app/test-pmd/testpmd.c
> >> @@ -1955,9 +1955,9 @@ fwd_stats_display(void)
> >> #ifdef RTE_TEST_PMD_RECORD_CORE_CYCLES
> >> #define CYC_PER_MHZ 1E6
> >> 	if (total_recv > 0)
> >> -		printf("\n  CPU cycles/packet=%u (total cycles="
> >> +		printf("\n  CPU cycles/packet=%.2f (total cycles="
> >> 		       "%"PRIu64" / total RX packets=%"PRIu64") at %lu MHz Clock\n",
> >> -		       (unsigned int)(fwd_cycles / total_recv),
> >> +		       (double)(fwd_cycles / (double)total_recv),
> >
> > Probably safer long double - to avoid overflow.
> 
> Is it possible for a ‘double' to be less than 8 bytes?

That was my initial thought - that on some 32 bit systems it could be 4B.
Though it seems I was wrong, so feel free to ignore.
BTW, what for double conversion, why not just:
double)(fwd_cycles /total_recv
?



> 
> >
> >> 		       fwd_cycles, total_recv, (uint64_t)(rte_get_tsc_hz() / CYC_PER_MHZ));
> >> #endif
> >> }
> >> --
> >> 2.20.1