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perf intel-pt: Fix timestamp following overflow
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timestamp_insn_cnt is used to estimate the timestamp based on the number of
instructions since the last known timestamp.

If the estimate is not accurate enough decoding might not be correctly
synchronized with side-band events causing more trace errors.

However there are always timestamps following an overflow, so the
estimate is not needed and can indeed result in more errors.

Suppress the estimate by setting timestamp_insn_cnt to zero.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/1520431349-30689-5-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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Adrian Hunter authored and Arnaldo Carvalho de Melo committed Mar 8, 2018
1 parent 1c196a6 commit 91d29b2
Showing 1 changed file with 1 addition and 0 deletions.
1 change: 1 addition & 0 deletions tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
Original file line number Diff line number Diff line change
Expand Up @@ -1378,6 +1378,7 @@ static int intel_pt_overflow(struct intel_pt_decoder *decoder)
intel_pt_clear_tx_flags(decoder);
decoder->have_tma = false;
decoder->cbr = 0;
decoder->timestamp_insn_cnt = 0;
decoder->pkt_state = INTEL_PT_STATE_ERR_RESYNC;
decoder->overflow = true;
return -EOVERFLOW;
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