Messages in this thread | | | From | kan.liang@linux ... | Subject | [PATCH 0/3] Convert TSC to monotonic clock for PEBS | Date | Mon, 23 Jan 2023 10:27:25 -0800 |
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From: Kan Liang <kan.liang@linux.intel.com>
A Processor Event Based Sampling (PEBS) record includes a field that provide the time stamp counter value when the counter was overflowed and the PEBS record was generated. The accurate time stamp can be used to reconcile user samples. However, the current PEBS codes only can convert the time stamp to sched_clock, which is not available from user space. A solution to convert a given TSC to user visible monotonic clock is required.
The perf_event subsystem only converts the TSC in a NMI handler. The converter function must be fast and NMI safe.
Considered the below two existing functions, but none of them fulfill the above requirements. - The ktime_get_mono_fast_ns() is NMI safe, but it can only return the current clock monotonic rather than a given time's monotonic. - The get_device_system_crosststamp() can calculate the system time from a given device time. But it's not fast and NMI safe.
Introduce a new generic interface, get_mono_fast_from_given_time, to convert a given timestamp to clock monotonic.
Kan Liang (3): timekeeping: NMI safe converter from a given time to monotonic x86/tsc: Add set_tsc_system_counterval perf/x86/intel/ds: Support monotonic clock for PEBS
arch/x86/events/intel/core.c | 2 +- arch/x86/events/intel/ds.c | 30 +++++++++++++--- arch/x86/include/asm/tsc.h | 1 + arch/x86/kernel/tsc.c | 6 ++++ include/linux/timekeeping.h | 9 +++++ kernel/time/timekeeping.c | 68 ++++++++++++++++++++++++++++++++++-- 6 files changed, 108 insertions(+), 8 deletions(-)
-- 2.35.1
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