On Sat, 2019-03-16 at 18:22 +0000, Wiles, Keith wrote: > > 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 : 10000 > > Ooops, too many parans and missed it. > > Then we can get a new version and that should be OK.
Yup, thanks for reviewing :-). > > 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 >
