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MTC packets are a new Intel PT feature. MTC packets provide finer grain timestamp information than TSC packets. Support for this feature is indicated by: /sys/bus/event_source/devices/intel_pt/caps/mtc which contains "1" if the feature is supported and "0" otherwise. MTC packets can be requested using a PMU config term e.g. perf record -e intel_pt/mtc/u sleep 1 The frequency of MTC packets can also be specified. e.g. perf record -e intel_pt/mtc,mtc_period=2/u sleep 1 The default value is 3 or the nearest lower value that is supported. 0 is always supported. Valid values are given by: /sys/bus/event_source/devices/intel_pt/caps/mtc_periods which contains a hexadecimal value, the bits of which represent valid values e.g. bit 2 set means value 2 is valid. The value is converted to the MTC frequency as: CTC-frequency / (2 ^ value) e.g. value 3 means one eighth of CTC-frequency Where CTC is the hardware crystal clock, the frequency of which can be related to TSC via values provided in cpuid leaf 0x15. If an invalid value is entered, the error message will give a list of valid values e.g. $ perf record -e intel_pt/mtc_period=15/u uname Invalid mtc_period for intel_pt. Valid values are: 0,3,6,9 tools/perf/Documentation/intel-pt.txt is updated in a later patch as there are a number of new features being added. For more information refer to the June 2015 or later Intel 64 and IA-32 Architectures SDM Chapter 36 Intel Processor Trace. Signed-off-by: Adrian Hunter <adrian.hunter@intel.com> Cc: Jiri Olsa <jolsa@redhat.com> Link: http://lkml.kernel.org/r/1437150840-31811-22-git-send-email-adrian.hunter@intel.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> |
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