From: Pavan Nikhilesh Bhagavatula <pbhagavatula@marvell.com>
To: "keith.wiles@intel.com" <keith.wiles@intel.com>
Cc: "stephen@networkplumber.org" <stephen@networkplumber.org>,
"thomas@monjalon.net" <thomas@monjalon.net>,
"dev@dpdk.org" <dev@dpdk.org>,
Jerin Jacob Kollanukkaran <jerinj@marvell.com>
Subject: Re: [dpdk-dev] [EXT] Re: [PATCH v2 2/2] eal: roundup tsc frequency when estimating it
Date: Sat, 16 Mar 2019 15:06:58 +0000 [thread overview]
Message-ID: <3e56d8dbbddfde0c48a26c6257af9c43a42f99dd.camel@marvell.com> (raw)
In-Reply-To: <86480C64-4ECD-4F4D-968E-5716D02D7D83@intel.com>
On Sat, 2019-03-16 at 14:42 +0000, Wiles, Keith wrote:
> > 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;
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."
> > }
> > #endif
> > return 0;
> > --
> > 2.21.0
> >
>
> Regards,
> Keith
>
next prev parent reply other threads:[~2019-03-16 15:07 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-29 8:32 [dpdk-dev] [PATCH] " Pavan Nikhilesh
2018-11-29 9:08 ` Jerin Jacob
2018-11-29 21:21 ` Stephen Hemminger
2018-11-30 7:17 ` Pavan Nikhilesh
2019-03-16 7:03 ` [dpdk-dev] [PATCH v2 1/2] eal: add macro to align value to the nearest multiple Pavan Nikhilesh Bhagavatula
2019-03-16 7:03 ` Pavan Nikhilesh Bhagavatula
2019-03-16 7:03 ` [dpdk-dev] [PATCH v2 2/2] eal: roundup tsc frequency when estimating it Pavan Nikhilesh Bhagavatula
2019-03-16 7:03 ` Pavan Nikhilesh Bhagavatula
2019-03-16 14:42 ` Wiles, Keith
2019-03-16 14:42 ` Wiles, Keith
2019-03-16 15:06 ` Pavan Nikhilesh Bhagavatula [this message]
2019-03-16 15:06 ` [dpdk-dev] [EXT] " Pavan Nikhilesh Bhagavatula
2019-03-16 17:18 ` Wiles, Keith
2019-03-16 17:18 ` Wiles, Keith
2019-03-16 17:56 ` Pavan Nikhilesh Bhagavatula
2019-03-16 17:56 ` Pavan Nikhilesh Bhagavatula
2019-03-16 18:22 ` Wiles, Keith
2019-03-16 18:22 ` Wiles, Keith
2019-03-16 18:27 ` Pavan Nikhilesh Bhagavatula
2019-03-16 18:27 ` Pavan Nikhilesh Bhagavatula
2019-03-16 19:01 ` [dpdk-dev] [PATCH v3 1/2] eal: add macro to align value to the nearest multiple Pavan Nikhilesh Bhagavatula
2019-03-16 19:01 ` Pavan Nikhilesh Bhagavatula
2019-03-16 19:01 ` [dpdk-dev] [PATCH v3 2/2] eal: roundup tsc frequency when estimating Pavan Nikhilesh Bhagavatula
2019-03-16 19:01 ` Pavan Nikhilesh Bhagavatula
2019-03-27 22:43 ` Thomas Monjalon
2019-03-27 22:43 ` Thomas Monjalon
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