From: Peter Zijlstra <peterz@infradead.org>
To: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Jiri Olsa <jolsa@redhat.com>,
linux-kernel@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, kvm@vger.kernel.org,
H Peter Anvin <hpa@zytor.com>,
Mathieu Poirier <mathieu.poirier@linaro.org>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Leo Yan <leo.yan@linaro.org>
Subject: Re: [PATCH 01/11] perf/x86: Fix native_perf_sched_clock_from_tsc() with __sched_clock_offset
Date: Wed, 9 Feb 2022 13:54:23 +0100 [thread overview]
Message-ID: <YgO5f8DFd2onnTOE@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20220209084929.54331-2-adrian.hunter@intel.com>
On Wed, Feb 09, 2022 at 10:49:19AM +0200, Adrian Hunter wrote:
> native_perf_sched_clock_from_tsc() is used to produce a time value that can
> be consistent with perf_clock(). Consequently, it should be adjusted by
> __sched_clock_offset, the same as perf_clock() would be.
>
> Fixes: 698eff6355f735 ("sched/clock, x86/perf: Fix perf test tsc")
> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
> ---
> arch/x86/kernel/tsc.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
> index a698196377be..c1c73fe324cd 100644
> --- a/arch/x86/kernel/tsc.c
> +++ b/arch/x86/kernel/tsc.c
> @@ -242,7 +242,8 @@ u64 native_sched_clock(void)
> */
> u64 native_sched_clock_from_tsc(u64 tsc)
> {
> - return cycles_2_ns(tsc);
> + return cycles_2_ns(tsc) +
> + (sched_clock_stable() ? __sched_clock_offset : 0);
> }
Why do we care about the !sched_clock_stable() case?
next prev parent reply other threads:[~2022-02-09 12:55 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-09 8:49 [PATCH 00/11] perf intel-pt: Add perf event clocks to better support VM tracing Adrian Hunter
2022-02-09 8:49 ` [PATCH 01/11] perf/x86: Fix native_perf_sched_clock_from_tsc() with __sched_clock_offset Adrian Hunter
2022-02-09 12:54 ` Peter Zijlstra [this message]
2022-02-09 14:26 ` Adrian Hunter
2022-02-09 8:49 ` [PATCH 02/11] perf/x86: Add support for TSC as a perf event clock Adrian Hunter
2022-02-09 13:11 ` Peter Zijlstra
2022-02-09 13:39 ` Adrian Hunter
2022-02-09 8:49 ` [PATCH 03/11] perf/x86: Add support for TSC in nanoseconds " Adrian Hunter
2022-02-09 13:00 ` Peter Zijlstra
2022-02-09 8:49 ` [PATCH 04/11] perf tools: Add new perf clock IDs Adrian Hunter
2022-02-09 8:49 ` [PATCH 05/11] perf tools: Add API probes for new " Adrian Hunter
2022-02-09 8:49 ` [PATCH 06/11] perf tools: Add new clock IDs to "perf time to TSC" test Adrian Hunter
2022-02-09 8:49 ` [PATCH 07/11] perf tools: Add perf_read_tsc_conv_for_clockid() Adrian Hunter
2022-02-09 8:49 ` [PATCH 08/11] perf intel-pt: Add support for new clock IDs Adrian Hunter
2022-02-09 8:49 ` [PATCH 09/11] perf intel-pt: Use CLOCK_PERF_HW_CLOCK_NS by default Adrian Hunter
2022-02-09 8:49 ` [PATCH 10/11] perf intel-pt: Add config variables for timing parameters Adrian Hunter
2022-02-09 8:49 ` [PATCH 11/11] perf intel-pt: Add documentation for new clock IDs Adrian Hunter
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