From: "Rafael J. Wysocki" <rafael@kernel.org>
To: Giovanni Gherdovich <ggherdovich@suse.cz>
Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Borislav Petkov <bp@suse.de>,
"Rafael J . Wysocki" <rjw@rjwysocki.net>,
"the arch/x86 maintainers" <x86@kernel.org>,
Linux PM <linux-pm@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Subject: Re: [PATCH v2 2/3] x86, sched: Bail out of frequency invariance if turbo frequency is unknown
Date: Wed, 3 Jun 2020 16:23:56 +0200 [thread overview]
Message-ID: <CAJZ5v0h8dWv6vzJ5k+Fg68s7M4UN1KrNvJ96ordG2MBh2A9M_w@mail.gmail.com> (raw)
In-Reply-To: <20200531182453.15254-3-ggherdovich@suse.cz>
On Sun, May 31, 2020 at 8:26 PM Giovanni Gherdovich <ggherdovich@suse.cz> wrote:
>
> There may be CPUs that support turbo boost but don't declare any turbo
> ratio, i.e. their MSR_TURBO_RATIO_LIMIT is all zeroes. In that condition
> scale-invariant calculations can't be performed.
>
> Signed-off-by: Giovanni Gherdovich <ggherdovich@suse.cz>
> Suggested-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
> Fixes: 1567c3e3467c ("x86, sched: Add support for frequency invariance")
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> ---
> arch/x86/kernel/smpboot.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
> index d660966d7de7..fe154c8226ba 100644
> --- a/arch/x86/kernel/smpboot.c
> +++ b/arch/x86/kernel/smpboot.c
> @@ -2001,9 +2001,11 @@ static bool intel_set_max_freq_ratio(void)
> /*
> * Some hypervisors advertise X86_FEATURE_APERFMPERF
> * but then fill all MSR's with zeroes.
> + * Some CPUs have turbo boost but don't declare any turbo ratio
> + * in MSR_TURBO_RATIO_LIMIT.
> */
> - if (!base_freq) {
> - pr_debug("Couldn't determine cpu base frequency, necessary for scale-invariant accounting.\n");
> + if (!base_freq || !turbo_freq) {
> + pr_debug("Couldn't determine cpu base or turbo frequency, necessary for scale-invariant accounting.\n");
> return false;
> }
>
> --
> 2.16.4
>
next prev parent reply other threads:[~2020-06-03 14:24 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-31 18:24 [PATCH v2 0/3] More frequency invariance fixes for x86 Giovanni Gherdovich
2020-05-31 18:24 ` [PATCH v2 1/3] x86, sched: check for counters overflow in frequency invariant accounting Giovanni Gherdovich
2020-06-03 14:22 ` Rafael J. Wysocki
2020-10-22 8:46 ` Peter Zijlstra
2020-10-22 12:21 ` Giovanni Gherdovich
2020-10-22 12:30 ` Peter Zijlstra
2020-05-31 18:24 ` [PATCH v2 2/3] x86, sched: Bail out of frequency invariance if turbo frequency is unknown Giovanni Gherdovich
2020-06-01 23:34 ` Ricardo Neri
2020-07-06 20:19 ` Ira Weiny
2020-06-03 14:23 ` Rafael J. Wysocki [this message]
2020-05-31 18:24 ` [PATCH v2 3/3] x86, sched: Bail out of frequency invariance if turbo_freq/base_freq gives 0 Giovanni Gherdovich
2020-06-03 14:51 ` Rafael J. Wysocki
2020-06-03 12:31 ` [PATCH v2 0/3] More frequency invariance fixes for x86 Peter Zijlstra
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