Commit f14445ee authored by Adrian Hunter's avatar Adrian Hunter Committed by Arnaldo Carvalho de Melo
Browse files

perf intel-pt: Support generating branch stack 



Add support for generating branch stack context for PT samples.  The
decoder reports a configurable number of branches as branch context for
each sample. Internally it keeps track of them by using a simple sliding
window.  We also flush the last branch buffer on each sample to avoid
overlapping intervals.

This is useful for:

- Reporting accurate basic block edge frequencies through the perf
  report branch view
- Using with --branch-history to get the wider context of samples
- Other users of LBRs

Also the Documentation is updated.

Examples:

	Record with Intel PT:

		perf record -e intel_pt//u ls

	Branch stacks are used by default if synthesized so:

		perf report --itrace=ile

	is the same as:

		perf report --itrace=ile -b

	Branch history can be requested also:

		perf report --itrace=igle --branch-history

Based-on-patch-by: default avatarAndi Kleen <ak@linux.intel.com>
Signed-off-by: default avatarAdrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/1443186956-18718-15-git-send-email-adrian.hunter@intel.com


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 385e3306

tools/perf/Documentation/intel-pt.txt

+10 −0
Original line number Diff line number Diff line
@@ -671,6 +671,7 @@ The letters are: 
	e	synthesize tracing error events

	d	create a debug log

	g	synthesize a call chain (use with i or x)

	l	synthesize last branch entries (use with i or x)



"Instructions" events look like they were recorded by "perf record -e

instructions".
@@ -718,6 +719,15 @@ transactions events can be specified. e.g. 
	--itrace=ig32

	--itrace=xg32



Also the number of last branch entries (default 64, max. 1024) for instructions or

transactions events can be specified. e.g.



       --itrace=il10

       --itrace=xl10



Note that last branch entries are cleared for each sample, so there is no overlap

from one sample to the next.



To disable trace decoding entirely, use the option --no-itrace.

tools/perf/util/intel-pt.c

+115 −0
Original line number Diff line number Diff line
@@ -22,6 +22,7 @@ 
#include "../perf.h"

#include "session.h"

#include "machine.h"

#include "sort.h"

#include "tool.h"

#include "event.h"

#include "evlist.h"
@@ -115,6 +116,9 @@ struct intel_pt_queue { 
	void *decoder;

	const struct intel_pt_state *state;

	struct ip_callchain *chain;

	struct branch_stack *last_branch;

	struct branch_stack *last_branch_rb;

	size_t last_branch_pos;

	union perf_event *event_buf;

	bool on_heap;

	bool stop;
@@ -675,6 +679,19 @@ static struct intel_pt_queue *intel_pt_alloc_queue(struct intel_pt *pt, 
			goto out_free;

	}



	if (pt->synth_opts.last_branch) {

		size_t sz = sizeof(struct branch_stack);



		sz += pt->synth_opts.last_branch_sz *

		      sizeof(struct branch_entry);

		ptq->last_branch = zalloc(sz);

		if (!ptq->last_branch)

			goto out_free;

		ptq->last_branch_rb = zalloc(sz);

		if (!ptq->last_branch_rb)

			goto out_free;

	}



	ptq->event_buf = malloc(PERF_SAMPLE_MAX_SIZE);

	if (!ptq->event_buf)

		goto out_free;
@@ -732,6 +749,8 @@ static struct intel_pt_queue *intel_pt_alloc_queue(struct intel_pt *pt, 


out_free:

	zfree(&ptq->event_buf);

	zfree(&ptq->last_branch);

	zfree(&ptq->last_branch_rb);

	zfree(&ptq->chain);

	free(ptq);

	return NULL;
@@ -746,6 +765,8 @@ static void intel_pt_free_queue(void *priv) 
	thread__zput(ptq->thread);

	intel_pt_decoder_free(ptq->decoder);

	zfree(&ptq->event_buf);

	zfree(&ptq->last_branch);

	zfree(&ptq->last_branch_rb);

	zfree(&ptq->chain);

	free(ptq);

}
@@ -876,6 +897,57 @@ static int intel_pt_setup_queues(struct intel_pt *pt) 
	return 0;

}



static inline void intel_pt_copy_last_branch_rb(struct intel_pt_queue *ptq)

{

	struct branch_stack *bs_src = ptq->last_branch_rb;

	struct branch_stack *bs_dst = ptq->last_branch;

	size_t nr = 0;



	bs_dst->nr = bs_src->nr;



	if (!bs_src->nr)

		return;



	nr = ptq->pt->synth_opts.last_branch_sz - ptq->last_branch_pos;

	memcpy(&bs_dst->entries[0],

	       &bs_src->entries[ptq->last_branch_pos],

	       sizeof(struct branch_entry) * nr);



	if (bs_src->nr >= ptq->pt->synth_opts.last_branch_sz) {

		memcpy(&bs_dst->entries[nr],

		       &bs_src->entries[0],

		       sizeof(struct branch_entry) * ptq->last_branch_pos);

	}

}



static inline void intel_pt_reset_last_branch_rb(struct intel_pt_queue *ptq)

{

	ptq->last_branch_pos = 0;

	ptq->last_branch_rb->nr = 0;

}



static void intel_pt_update_last_branch_rb(struct intel_pt_queue *ptq)

{

	const struct intel_pt_state *state = ptq->state;

	struct branch_stack *bs = ptq->last_branch_rb;

	struct branch_entry *be;



	if (!ptq->last_branch_pos)

		ptq->last_branch_pos = ptq->pt->synth_opts.last_branch_sz;



	ptq->last_branch_pos -= 1;



	be              = &bs->entries[ptq->last_branch_pos];

	be->from        = state->from_ip;

	be->to          = state->to_ip;

	be->flags.abort = !!(state->flags & INTEL_PT_ABORT_TX);

	be->flags.in_tx = !!(state->flags & INTEL_PT_IN_TX);

	/* No support for mispredict */



	if (bs->nr < ptq->pt->synth_opts.last_branch_sz)

		bs->nr += 1;

}



static int intel_pt_inject_event(union perf_event *event,

				 struct perf_sample *sample, u64 type,

				 bool swapped)
@@ -890,6 +962,10 @@ static int intel_pt_synth_branch_sample(struct intel_pt_queue *ptq) 
	struct intel_pt *pt = ptq->pt;

	union perf_event *event = ptq->event_buf;

	struct perf_sample sample = { .ip = 0, };

	struct dummy_branch_stack {

		u64			nr;

		struct branch_entry	entries;

	} dummy_bs;



	if (pt->branches_filter && !(pt->branches_filter & ptq->flags))

		return 0;
@@ -912,6 +988,21 @@ static int intel_pt_synth_branch_sample(struct intel_pt_queue *ptq) 
	sample.flags = ptq->flags;

	sample.insn_len = ptq->insn_len;



	/*

	 * perf report cannot handle events without a branch stack when using

	 * SORT_MODE__BRANCH so make a dummy one.

	 */

	if (pt->synth_opts.last_branch && sort__mode == SORT_MODE__BRANCH) {

		dummy_bs = (struct dummy_branch_stack){

			.nr = 1,

			.entries = {

				.from = sample.ip,

				.to = sample.addr,

			},

		};

		sample.branch_stack = (struct branch_stack *)&dummy_bs;

	}



	if (pt->synth_opts.inject) {

		ret = intel_pt_inject_event(event, &sample,

					    pt->branches_sample_type,
@@ -961,6 +1052,11 @@ static int intel_pt_synth_instruction_sample(struct intel_pt_queue *ptq) 
		sample.callchain = ptq->chain;

	}



	if (pt->synth_opts.last_branch) {

		intel_pt_copy_last_branch_rb(ptq);

		sample.branch_stack = ptq->last_branch;

	}



	if (pt->synth_opts.inject) {

		ret = intel_pt_inject_event(event, &sample,

					    pt->instructions_sample_type,
@@ -974,6 +1070,9 @@ static int intel_pt_synth_instruction_sample(struct intel_pt_queue *ptq) 
		pr_err("Intel Processor Trace: failed to deliver instruction event, error %d\n",

		       ret);



	if (pt->synth_opts.last_branch)

		intel_pt_reset_last_branch_rb(ptq);



	return ret;

}
@@ -1008,6 +1107,11 @@ static int intel_pt_synth_transaction_sample(struct intel_pt_queue *ptq) 
		sample.callchain = ptq->chain;

	}



	if (pt->synth_opts.last_branch) {

		intel_pt_copy_last_branch_rb(ptq);

		sample.branch_stack = ptq->last_branch;

	}



	if (pt->synth_opts.inject) {

		ret = intel_pt_inject_event(event, &sample,

					    pt->transactions_sample_type,
@@ -1021,6 +1125,9 @@ static int intel_pt_synth_transaction_sample(struct intel_pt_queue *ptq) 
		pr_err("Intel Processor Trace: failed to deliver transaction event, error %d\n",

		       ret);



	if (pt->synth_opts.callchain)

		intel_pt_reset_last_branch_rb(ptq);



	return ret;

}
@@ -1116,6 +1223,9 @@ static int intel_pt_sample(struct intel_pt_queue *ptq) 
			return err;

	}



	if (pt->synth_opts.last_branch)

		intel_pt_update_last_branch_rb(ptq);



	if (!pt->sync_switch)

		return 0;
@@ -1763,6 +1873,8 @@ static int intel_pt_synth_events(struct intel_pt *pt, 
		pt->instructions_sample_period = attr.sample_period;

		if (pt->synth_opts.callchain)

			attr.sample_type |= PERF_SAMPLE_CALLCHAIN;

		if (pt->synth_opts.last_branch)

			attr.sample_type |= PERF_SAMPLE_BRANCH_STACK;

		pr_debug("Synthesizing 'instructions' event with id %" PRIu64 " sample type %#" PRIx64 "\n",

			 id, (u64)attr.sample_type);

		err = intel_pt_synth_event(session, &attr, id);
@@ -1782,6 +1894,8 @@ static int intel_pt_synth_events(struct intel_pt *pt, 
		attr.sample_period = 1;

		if (pt->synth_opts.callchain)

			attr.sample_type |= PERF_SAMPLE_CALLCHAIN;

		if (pt->synth_opts.last_branch)

			attr.sample_type |= PERF_SAMPLE_BRANCH_STACK;

		pr_debug("Synthesizing 'transactions' event with id %" PRIu64 " sample type %#" PRIx64 "\n",

			 id, (u64)attr.sample_type);

		err = intel_pt_synth_event(session, &attr, id);
@@ -1808,6 +1922,7 @@ static int intel_pt_synth_events(struct intel_pt *pt, 
		attr.sample_period = 1;

		attr.sample_type |= PERF_SAMPLE_ADDR;

		attr.sample_type &= ~(u64)PERF_SAMPLE_CALLCHAIN;

		attr.sample_type &= ~(u64)PERF_SAMPLE_BRANCH_STACK;

		pr_debug("Synthesizing 'branches' event with id %" PRIu64 " sample type %#" PRIx64 "\n",

			 id, (u64)attr.sample_type);

		err = intel_pt_synth_event(session, &attr, id);

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