> On Mar 16, 2019, at 12:56 PM, Pavan Nikhilesh Bhagavatula > <pbhagavat...@marvell.com> wrote: > > On Sat, 2019-03-16 at 17:18 +0000, Wiles, Keith wrote: >>> On Mar 16, 2019, at 10:06 AM, Pavan Nikhilesh Bhagavatula < >>> pbhagavat...@marvell.com> wrote: >>> >>> On Sat, 2019-03-16 at 14:42 +0000, Wiles, Keith wrote: >>>>> On Mar 16, 2019, at 2:03 AM, Pavan Nikhilesh Bhagavatula < >>>>> pbhagavat...@marvell.com> wrote: >>>>> >>>>> From: Pavan Nikhilesh <pbhagavat...@marvell.com> >>>>> >>>>> When estimating tsc frequency using sleep/gettime round it up >>>>> to >>>>> the >>>>> nearest multiple of 10Mhz for more accuracy. >> >> How does rounding up the TSC value become more accurate, If the value >> is 1 cycles more then it should be then your macro would round down >> and if it is 1 cycle greater than 1E7 it would round up. > > Example in case of RTE_ARM_EAL_RDTSC_USE_PMU enabled > > Before roundup : 1400000979 > After roundup : 1400000000 > EAL: TSC frequency is ~1400000000 Hz > > > Before roundup : 1399999060 > After roundup : 1400000000 > EAL: TSC frequency is ~1400000000 Hz > >>>>> Signed-off-by: Pavan Nikhilesh <pbhagavat...@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(-) >> >> It appears you did not use the head of the master as linuxapp is now >> just linux and freebsdapp is freebsd. You need to rebase to the head >> of master and send a new version. >>>>> 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); >> >> The 1E7 is a magic number convert this to a meaningful define. > > 1E7 ~ 10Mhz will convert to a macro. > >>>>> } >>>>> >>>>> 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; >>> >>> I missed this log will remove it in the next version. >>> >>>>> } >>>>> >>>>> 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. >>> >>> Since in this function nanosleep might not be cycle accurate we >>> need to >>> round it up. >>> >>> Please note that estimation only applies when get_tsc_freq_arch() >>> fails. i.e there is no CPU instruction that specifies the cyc/sec. >>> >>> As I mentioned in the patch notes >>> "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 clock of PMU and eal falls back to >>> sleep(1)/nanosleep.” >> >> OK, I looked at the changes and the code for setting the TSC again. I >> would have not handled the setting of TSC in the way it was done, but >> that is not your problem. I agree the changes do look ok, the only >> problem I have is the new macro will roundup or down depending on the >> value. In your statement you are wanting to roundup the values. >> >> If the sleep/nanosleep is less than a second for some reason, then >> your macro would round it down is that what we wanted? I guess my >> point is you are assuming the TSC calculation will always be less >> than a second (with sleep) and the macro would round up depending on >> the value calculated using the sleep/nanosleep. >> >> I was playing with these MUL macros and I am not sure they do what we >> expect in the case of the multiple value is much closer to the value >> passed. >> >> If we have a v = 10001 and multiple to 1000 we have the following: >> >> RTE_ALIGN_MUL_CEIL(10001, 1000) >> (10001 + (1000 - 1)) / (1000 * 1000) > ((10001 + (1000 - 1)) / 1000) * 1000 >> (10001 + 999) / 1000000 >> 20000 / 1000000 >> Result: 0 > > ((10001 + (1000 - 1) / 1000) * 1000 > ((10001 + 999) / 1000) * 1000 > (11000/1000) * 1000 > 11 * 1000 > > Result : 11000 > >> >> RTE_ALIGN_MUL_FLOOR(10001, 1000) >> (10001 / (1000 * 1000)) > (10001 / 1000) * 1000 >> (10001 / 1000000) >> Result: 0 > 10.001 * 1000 > > Result : 1000
Ooops, too many parans and missed it. Then we can get a new version and that should be OK. I will add my $0.02 then: Reviewed-by: Keith Wiles<keith.wiles> > >> >> Unless I am wrong here the value v must be over a 1,000,000 to make >> these macros work or the value v to be greater than (mul * mul) in >> all cases or zero is the result. It may work for the TSC values as we >> are using a small mul value compared to the TSC value. If DPDK was >> ported to a slower machine it could be also zero. > > Unless we have machines that run at freq < 10Mhz this scheme will > always work. > If we have such machines lets hope that they have a CPU instruction > that tells us the cyc/sec. > >> >> I think we need to fix the macros and rethink how TSC is set here. >> >>>>> } >>>>> #endif >>>>> return 0; >>>>> -- >>>>> 2.21.0 >>>>> >>>> >>>> Regards, >>>> Keith >> >> Regards, >> Keith >> > > Regards, > Pavan. Regards, Keith