On Tue, Oct 1, 2024 at 11:01 PM Bruce Richardson
<bruce.richard...@intel.com> wrote:
>
> On Tue, Oct 01, 2024 at 03:22:51AM +0300, Isaac Boukris wrote:
> > If the tsc_known_freq cpu flag is missing, it means the kernel doesn't
> > trust it and calculates its own. We should do the same to avoid drift.
> >
> > Signed-off-by: Isaac Boukris <ibouk...@gmail.com>
> > ---
> > lib/eal/common/eal_common_timer.c | 3 +-
> > lib/eal/common/eal_private.h | 2 +-
> > lib/eal/freebsd/eal_timer.c | 5 ++-
> > lib/eal/linux/eal_timer.c | 53 +++++++++++++++++++++++++++++--
> > lib/eal/windows/eal_timer.c | 5 ++-
> > 5 files changed, 60 insertions(+), 8 deletions(-)
> >
> > diff --git a/lib/eal/common/eal_common_timer.c
> > b/lib/eal/common/eal_common_timer.c
> > index c5c4703f15..e00be0a5c8 100644
> > --- a/lib/eal/common/eal_common_timer.c
> > +++ b/lib/eal/common/eal_common_timer.c
> > @@ -66,8 +66,7 @@ set_tsc_freq(void)
> > }
> >
> > freq = get_tsc_freq_arch();
> > - if (!freq)
> > - freq = get_tsc_freq();
> > + freq = get_tsc_freq(freq);
> > if (!freq)
> > freq = estimate_tsc_freq();
> >
> > diff --git a/lib/eal/common/eal_private.h b/lib/eal/common/eal_private.h
> > index af09620426..bb315dab04 100644
> > --- a/lib/eal/common/eal_private.h
> > +++ b/lib/eal/common/eal_private.h
> > @@ -374,7 +374,7 @@ void set_tsc_freq(void);
> > *
> > * This function is private to the EAL.
> > */
> > -uint64_t get_tsc_freq(void);
> > +uint64_t get_tsc_freq(uint64_t arch_hz);
> >
> > /**
> > * Get TSC frequency if the architecture supports.
> > diff --git a/lib/eal/freebsd/eal_timer.c b/lib/eal/freebsd/eal_timer.c
> > index 3dd70e24ba..5a8aea03e1 100644
> > --- a/lib/eal/freebsd/eal_timer.c
> > +++ b/lib/eal/freebsd/eal_timer.c
> > @@ -26,12 +26,15 @@
> > enum timer_source eal_timer_source = EAL_TIMER_TSC;
> >
> > uint64_t
> > -get_tsc_freq(void)
> > +get_tsc_freq(uint64_t arch_hz)
> > {
> > size_t sz;
> > int tmp;
> > uint64_t tsc_hz;
> >
> > + if (arch_hz)
> > + return arch_hz;
> > +
> > sz = sizeof(tmp);
> > tmp = 0;
> >
>
> On FreeBSD I'm not sure this is the best behaviour. On BSD we read the TSC
> value from the kernel, which, one assumes, has measured it accurately.
> Therefore I'd tend toward just using the kernel value in all cases, maybe
> check the arch value (if non-zero) against that and warning if they have
> significant divergence. WDYT?
Makes sense, I'll add a patch for that. We could also use the arch
value if for some reason the sysctlbyname() failed.
