diff options
| author | Adrian Hunter <adrian.hunter@intel.com> | 2013-06-28 16:22:18 +0300 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2013-07-23 12:17:45 +0200 |
| commit | c73deb6aecda2955716f31572516f09d930ef450 (patch) | |
| tree | 037f7945cb4289545d5ffbe9506e071a83d6c1a6 /arch/x86/kernel/cpu/perf_event.c | |
| parent | 860f085b74e9f0075de8140ed3a1e5b5e3e39aa8 (diff) | |
perf/x86: Add ability to calculate TSC from perf sample timestamps
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>
Diffstat (limited to 'arch/x86/kernel/cpu/perf_event.c')
| -rw-r--r-- | arch/x86/kernel/cpu/perf_event.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c index a7c7305030cc..8355c84b9729 100644 --- a/arch/x86/kernel/cpu/perf_event.c +++ b/arch/x86/kernel/cpu/perf_event.c @@ -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); + } } /* |