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Date: Wed, 9 Feb 2022 16:26:02 +0200 From: Adrian Hunter <adrian.hunter@...el.com> To: Peter Zijlstra <peterz@...radead.org> Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Arnaldo Carvalho de Melo <acme@...nel.org>, Jiri Olsa <jolsa@...hat.com>, linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, kvm@...r.kernel.org, H Peter Anvin <hpa@...or.com>, Mathieu Poirier <mathieu.poirier@...aro.org>, Suzuki K Poulose <suzuki.poulose@....com>, Leo Yan <leo.yan@...aro.org> Subject: Re: [PATCH 01/11] perf/x86: Fix native_perf_sched_clock_from_tsc() with __sched_clock_offset On 09/02/2022 14:54, Peter Zijlstra wrote: > 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@...el.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? I guess we don't. So add __sched_clock_offset unconditionally then?
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