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perf/x86: Add ability to calculate TSC from perf sample timestamps

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For modern CPUs, perf clock is directly related to TSC.  TSC
can be calculated from perf clock and vice versa using a simple
calculation.  Two of the three componenets of that calculation
are already exported in struct perf_event_mmap_page.  This patch
exports the third.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Link: http://lkml.kernel.org/r/1372425741-1676-3-git-send-email-adrian.hunter@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Adrian Hunter
2013-06-28 16:22:18 +03:00
committed by Ingo Molnar
parent 860f085b74
commit c73deb6aec
4 changed files with 33 additions and 2 deletions
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6
arch/x86/kernel/cpu/perf_event.c
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@@ -1884,6 +1884,7 @@ static struct pmu pmu = {
void arch_perf_update_userpage(struct perf_event_mmap_page *userpg, u64 now)
{
userpg->cap_usr_time = 0;
userpg->cap_usr_time_zero = 0;
userpg->cap_usr_rdpmc = x86_pmu.attr_rdpmc;
userpg->pmc_width = x86_pmu.cntval_bits;
@@ -1897,6 +1898,11 @@ void arch_perf_update_userpage(struct perf_event_mmap_page *userpg, u64 now)
userpg->time_mult = this_cpu_read(cyc2ns);
userpg->time_shift = CYC2NS_SCALE_FACTOR;
userpg->time_offset = this_cpu_read(cyc2ns_offset) - now;
if (sched_clock_stable && !check_tsc_disabled()) {
userpg->cap_usr_time_zero = 1;
userpg->time_zero = this_cpu_read(cyc2ns_offset);
}
}
/*