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Normally, for cycle-acccurate mode, IPC values are an exact number of instructions and cycles. Due to the granularity of timestamps, that happens only when a CYC packet correlates to the event. Support the itrace 'A' option, to use instead, the number of cycles associated with the current timestamp. This provides IPC information for every change of timestamp, but at the expense of accuracy. Due to the granularity of timestamps, the actual number of cycles increases even though the cycles reported does not. The number of instructions is known, but if IPC is reported, cycles can be too low and so IPC is too high. Note that inaccuracy decreases as the period of sampling increases i.e. if the number of cycles is too low by a small amount, that becomes less significant if the number of cycles is large. Furthermore, it can be used in conjunction with dlfilter-show-cycles.so to provide higher granularity cycle information. Reviewed-by: Andi Kleen <ak@linux.intel.com> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com> Cc: Jiri Olsa <jolsa@redhat.com> Link: https://lore.kernel.org/r/20211027080334.365596-4-adrian.hunter@intel.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> |
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