Commit 347a7389 authored by Adrian Hunter's avatar Adrian Hunter Committed by Arnaldo Carvalho de Melo
Browse files

perf intel-pt: Add support for decoding PSB+ only 



A single q option decodes ip from only FUP/TIP packets. Make it so that
repeating the q option (i.e. qq) decodes only PSB+, getting ip if there
is a FUP packet within PSB+ (i.e. between PSB and PSBEND).

Example:

 $ perf record -e intel_pt//u grep -rI pudding drivers
 [ perf record: Woken up 52 times to write data ]
 [ perf record: Captured and wrote 57.870 MB perf.data ]
 $ time perf script --itrace=bi | wc -l
 58948289

 real    1m23.863s
 user    1m23.251s
 sys     0m7.452s
 $ time perf script --itrace=biq | wc -l
 3385694

 real    0m4.453s
 user    0m4.455s
 sys     0m0.328s
 $ time perf script --itrace=biqq | wc -l
 1883

 real    0m0.047s
 user    0m0.043s
 sys     0m0.009s

Signed-off-by: default avatarAdrian Hunter <adrian.hunter@intel.com>
Reviewed-by: default avatarAndi Kleen <ak@linux.intel.com>
Tested-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lore.kernel.org/lkml/20200710151104.15137-13-adrian.hunter@intel.com


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 7c1b16ba

tools/perf/Documentation/perf-intel-pt.txt

+15 −0
Original line number Diff line number Diff line
@@ -999,6 +999,21 @@ What *will* be decoded with the (single) q option: 
Note the q option does not specify what events will be synthesized e.g. the p

option must be used also to show power events.



Repeating the q option (double-q i.e. qq) results in even faster decoding and even

less detail.  The decoder decodes only extended PSB (PSB+) packets, getting the

instruction pointer if there is a FUP packet within PSB+ (i.e. between PSB and

PSBEND).  Note PSB packets occur regularly in the trace based on the psb_period

config term (refer config terms section).  There will be a FUP packet if the

PSB+ occurs while control flow is being traced.



What will *not* be decoded with the qq option:



	- everything except instruction pointer associated with PSB packets



What *will* be decoded with the qq option:



	- instruction pointer associated with PSB packets





dump option

~~~~~~~~~~~

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

+18 −0
Original line number Diff line number Diff line
@@ -113,6 +113,7 @@ struct intel_pt_decoder { 
	bool in_psb;

	bool hop;

	bool hop_psb_fup;

	bool leap;

	enum intel_pt_param_flags flags;

	uint64_t pos;

	uint64_t last_ip;
@@ -240,6 +241,7 @@ struct intel_pt_decoder *intel_pt_decoder_new(struct intel_pt_params *params) 
	decoder->return_compression = params->return_compression;

	decoder->branch_enable      = params->branch_enable;

	decoder->hop                = params->quick >= 1;

	decoder->leap               = params->quick >= 2;



	decoder->flags              = params->flags;
@@ -1903,9 +1905,18 @@ static int intel_pt_resample(struct intel_pt_decoder *decoder) 
#define HOP_RETURN	2

#define HOP_AGAIN	3



static int intel_pt_scan_for_psb(struct intel_pt_decoder *decoder);



/* Hop mode: Ignore TNT, do not walk code, but get ip from FUPs and TIPs */

static int intel_pt_hop_trace(struct intel_pt_decoder *decoder, bool *no_tip, int *err)

{

	/* Leap from PSB to PSB, getting ip from FUP within PSB+ */

	if (decoder->leap && !decoder->in_psb && decoder->packet.type != INTEL_PT_PSB) {

		*err = intel_pt_scan_for_psb(decoder);

		if (*err)

			return HOP_RETURN;

	}



	switch (decoder->packet.type) {

	case INTEL_PT_TNT:

		return HOP_IGNORE;
@@ -2681,6 +2692,7 @@ static int intel_pt_sync(struct intel_pt_decoder *decoder) 
	decoder->ip = 0;

	intel_pt_clear_stack(&decoder->stack);



leap:

	err = intel_pt_scan_for_psb(decoder);

	if (err)

		return err;
@@ -2702,6 +2714,12 @@ static int intel_pt_sync(struct intel_pt_decoder *decoder) 
			decoder->pkt_state = INTEL_PT_STATE_RESAMPLE;

		else

			decoder->pkt_state = INTEL_PT_STATE_IN_SYNC;

	} else if (decoder->leap) {

		/*

		 * In leap mode, only PSB+ is decoded, so keeping leaping to the

		 * next PSB until there is an ip.

		 */

		goto leap;

	} else {

		return intel_pt_sync_ip(decoder);

	}