> -----Original Message-----
> From: Dharmik Thakkar <dharmik.thak...@arm.com>
> Sent: Friday, May 8, 2020 6:37 PM
> To: Ananyev, Konstantin <konstantin.anan...@intel.com>
> Cc: Lu, Wenzhuo <wenzhuo...@intel.com>; Wu, Jingjing <jingjing...@intel.com>;
> Iremonger, Bernard <bernard.iremon...@intel.com>;
> dev@dpdk.org; nd <n...@arm.com>
> Subject: Re: [dpdk-dev] [PATCH 2/5] app/testpmd: print fractional part in CPU
> cycles
>
>
>
> > On May 8, 2020, at 12:17 PM, Ananyev, Konstantin
> > <konstantin.anan...@intel.com> wrote:
> >
> >> Hi Konstantin,
> >>
> >>> On May 7, 2020, at 4:50 AM, Ananyev, Konstantin
> >>> <konstantin.anan...@intel.com> wrote:
> >>>
> >>>
> >>>
> >>>> -----Original Message-----
> >>>> From: dev <dev-boun...@dpdk.org> On Behalf Of Dharmik Thakkar
> >>>> Sent: Wednesday, May 6, 2020 10:59 PM
> >>>> To: Lu, Wenzhuo <wenzhuo...@intel.com>; Wu, Jingjing
> >>>> <jingjing...@intel.com>; Iremonger, Bernard
> <bernard.iremon...@intel.com>
> >>>> Cc: dev@dpdk.org; n...@arm.com; Dharmik Thakkar <dharmik.thak...@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.thak...@arm.com>
> >>>> Reviewed-by: Honnappa Nagarahalli <honnappa.nagaraha...@arm.com>
> >>>> Reviewed-by: Phil Yang <phil.y...@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
> > ?
>
> Without (double) total recv, I will always get the fractional part as .00.
> For the above example, with (double)(fwd_cycles / total_recv), I see 14.00
> instead of 14.28
AFAIK, that's because that way you told compiler to do integer division and
then convert result to double.
While (double)fwd_cycles /total_recv, will tell compiler to explicitly convert
fwd_cycles to double
and compiler will implicitly do the same for total_recv too, and result will be
double too.
>
> >
> >
> >
> >>
> >>>
> >>>> fwd_cycles, total_recv, (uint64_t)(rte_get_tsc_hz() /
> >>>> CYC_PER_MHZ));
> >>>> #endif
> >>>> }
> >>>> --
> >>>> 2.20.1
