Commit 3bccbe20 authored by Adrian Hunter's avatar Adrian Hunter Committed by Arnaldo Carvalho de Melo
Browse files

perf intel-pt: Fix MTC timestamp calculation for large MTC periods 



The MTC packet provides a 8-bit slice of CTC which is related to TSC by
the TMA packet, however the TMA packet only provides the lower 16 bits
of CTC.  If mtc_shift > 8 then some of the MTC bits are not in the CTC
provided by the TMA packet. Fix-up the last_mtc calculated from the TMA
packet by copying the missing bits from the current MTC assuming the
least difference between the two, and that the current MTC comes after
last_mtc.

Signed-off-by: default avatarAdrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: stable@vger.kernel.org # v4.3+
Link: http://lkml.kernel.org/r/1475062896-22274-2-git-send-email-adrian.hunter@intel.com


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 51ee6481

tools/perf/util/intel-pt-decoder/intel-pt-decoder.c

+36 −0
Original line number Diff line number Diff line
@@ -90,6 +90,7 @@ struct intel_pt_decoder { 
	bool pge;

	bool have_tma;

	bool have_cyc;

	bool fixup_last_mtc;

	uint64_t pos;

	uint64_t last_ip;

	uint64_t ip;
@@ -586,10 +587,31 @@ struct intel_pt_calc_cyc_to_tsc_info { 
	uint64_t        tsc_timestamp;

	uint64_t        timestamp;

	bool            have_tma;

	bool            fixup_last_mtc;

	bool            from_mtc;

	double          cbr_cyc_to_tsc;

};



/*

 * MTC provides a 8-bit slice of CTC but the TMA packet only provides the lower

 * 16 bits of CTC. If mtc_shift > 8 then some of the MTC bits are not in the CTC

 * provided by the TMA packet. Fix-up the last_mtc calculated from the TMA

 * packet by copying the missing bits from the current MTC assuming the least

 * difference between the two, and that the current MTC comes after last_mtc.

 */

static void intel_pt_fixup_last_mtc(uint32_t mtc, int mtc_shift,

				    uint32_t *last_mtc)

{

	uint32_t first_missing_bit = 1U << (16 - mtc_shift);

	uint32_t mask = ~(first_missing_bit - 1);



	*last_mtc |= mtc & mask;

	if (*last_mtc >= mtc) {

		*last_mtc -= first_missing_bit;

		*last_mtc &= 0xff;

	}

}



static int intel_pt_calc_cyc_cb(struct intel_pt_pkt_info *pkt_info)

{

	struct intel_pt_decoder *decoder = pkt_info->decoder;
@@ -619,6 +641,11 @@ static int intel_pt_calc_cyc_cb(struct intel_pt_pkt_info *pkt_info) 
			return 0;



		mtc = pkt_info->packet.payload;

		if (decoder->mtc_shift > 8 && data->fixup_last_mtc) {

			data->fixup_last_mtc = false;

			intel_pt_fixup_last_mtc(mtc, decoder->mtc_shift,

						&data->last_mtc);

		}

		if (mtc > data->last_mtc)

			mtc_delta = mtc - data->last_mtc;

		else
@@ -687,6 +714,7 @@ static int intel_pt_calc_cyc_cb(struct intel_pt_pkt_info *pkt_info) 


		data->ctc_delta = 0;

		data->have_tma = true;

		data->fixup_last_mtc = true;



		return 0;
@@ -753,6 +781,7 @@ static void intel_pt_calc_cyc_to_tsc(struct intel_pt_decoder *decoder, 
		.tsc_timestamp  = decoder->tsc_timestamp,

		.timestamp      = decoder->timestamp,

		.have_tma       = decoder->have_tma,

		.fixup_last_mtc = decoder->fixup_last_mtc,

		.from_mtc       = from_mtc,

		.cbr_cyc_to_tsc = 0,

	};
@@ -1271,6 +1300,7 @@ static void intel_pt_calc_tma(struct intel_pt_decoder *decoder) 
	}

	decoder->ctc_delta = 0;

	decoder->have_tma = true;

	decoder->fixup_last_mtc = true;

	intel_pt_log("CTC timestamp " x64_fmt " last MTC %#x  CTC rem %#x\n",

		     decoder->ctc_timestamp, decoder->last_mtc, ctc_rem);

}
@@ -1285,6 +1315,12 @@ static void intel_pt_calc_mtc_timestamp(struct intel_pt_decoder *decoder) 


	mtc = decoder->packet.payload;



	if (decoder->mtc_shift > 8 && decoder->fixup_last_mtc) {

		decoder->fixup_last_mtc = false;

		intel_pt_fixup_last_mtc(mtc, decoder->mtc_shift,

					&decoder->last_mtc);

	}



	if (mtc > decoder->last_mtc)

		mtc_delta = mtc - decoder->last_mtc;

	else