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authorAdrian Hunter <adrian.hunter@intel.com>2021-10-27 11:03:31 +0300
committerArnaldo Carvalho de Melo <acme@redhat.com>2021-10-27 16:20:18 -0300
commitf2b91386ffe66dba0860c03c9dec1c6b45c2daba (patch)
tree9bcb97a668973e948f114336089644cbdb39ddd7 /tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
parentb6778fe1bbe486e65439a50226b5c7b70dc11d94 (diff)
downloadlinux-next-f2b91386ffe66dba0860c03c9dec1c6b45c2daba.tar.gz
perf intel-pt: Support itrace A option to approximate IPC
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>
Diffstat (limited to 'tools/perf/util/intel-pt-decoder/intel-pt-decoder.c')
-rw-r--r--tools/perf/util/intel-pt-decoder/intel-pt-decoder.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c b/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
index 5ab631702769..5f83937bf8f3 100644
--- a/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
+++ b/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
@@ -608,6 +608,7 @@ static inline void intel_pt_update_sample_time(struct intel_pt_decoder *decoder)
{
decoder->sample_timestamp = decoder->timestamp;
decoder->sample_insn_cnt = decoder->timestamp_insn_cnt;
+ decoder->state.cycles = decoder->tot_cyc_cnt;
}
static void intel_pt_reposition(struct intel_pt_decoder *decoder)