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perf intel-pt: Add support for PERF_RECORD_SWITCH
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Add support for selecting and processing PERF_RECORD_SWITCH events for
use by Intel PT.  If they are available, they will be used in preference
to sched_switch events.

This enables an unprivileged user to trace multi-threaded or
multi-process workloads with any level of perf_event_paranoid.  However
it depends on kernel support for PERF_RECORD_SWITCH.

Without this patch, tracing a multi-threaded workload will decode
without error but all the data will be attributed to the main thread.

Without this patch, tracing a multi-process workload will result in
decoder errors because the decoder will not know which executable is
executing.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/1439458857-30636-3-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 Sep 4, 2015
1 parent 1b29ac5 commit 86c2786
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Showing 2 changed files with 151 additions and 33 deletions.
55 changes: 47 additions & 8 deletions tools/perf/arch/x86/util/intel-pt.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -624,13 +624,49 @@ static int intel_pt_recording_options(struct auxtrace_record *itr,
* threads.
*/
if (have_timing_info && !cpu_map__empty(cpus)) {
err = intel_pt_track_switches(evlist);
if (err == -EPERM)
pr_debug2("Unable to select sched:sched_switch\n");
else if (err)
return err;
else
ptr->have_sched_switch = 1;
if (perf_can_record_switch_events()) {
bool cpu_wide = !target__none(&opts->target) &&
!target__has_task(&opts->target);

if (!cpu_wide && perf_can_record_cpu_wide()) {
struct perf_evsel *switch_evsel;

err = parse_events(evlist, "dummy:u", NULL);
if (err)
return err;

switch_evsel = perf_evlist__last(evlist);

switch_evsel->attr.freq = 0;
switch_evsel->attr.sample_period = 1;
switch_evsel->attr.context_switch = 1;

switch_evsel->system_wide = true;
switch_evsel->no_aux_samples = true;
switch_evsel->immediate = true;

perf_evsel__set_sample_bit(switch_evsel, TID);
perf_evsel__set_sample_bit(switch_evsel, TIME);
perf_evsel__set_sample_bit(switch_evsel, CPU);

opts->record_switch_events = false;
ptr->have_sched_switch = 3;
} else {
opts->record_switch_events = true;
if (cpu_wide)
ptr->have_sched_switch = 3;
else
ptr->have_sched_switch = 2;
}
} else {
err = intel_pt_track_switches(evlist);
if (err == -EPERM)
pr_debug2("Unable to select sched:sched_switch\n");
else if (err)
return err;
else
ptr->have_sched_switch = 1;
}
}

if (intel_pt_evsel) {
Expand Down Expand Up @@ -663,8 +699,11 @@ static int intel_pt_recording_options(struct auxtrace_record *itr,
tracking_evsel->attr.sample_period = 1;

/* In per-cpu case, always need the time of mmap events etc */
if (!cpu_map__empty(cpus))
if (!cpu_map__empty(cpus)) {
perf_evsel__set_sample_bit(tracking_evsel, TIME);
/* And the CPU for switch events */
perf_evsel__set_sample_bit(tracking_evsel, CPU);
}
}

/*
Expand Down
129 changes: 104 additions & 25 deletions tools/perf/util/intel-pt.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1145,11 +1145,13 @@ static int intel_pt_sample(struct intel_pt_queue *ptq)
return 0;
}

static u64 intel_pt_switch_ip(struct machine *machine, u64 *ptss_ip)
static u64 intel_pt_switch_ip(struct intel_pt *pt, u64 *ptss_ip)
{
struct machine *machine = pt->machine;
struct map *map;
struct symbol *sym, *start;
u64 ip, switch_ip = 0;
const char *ptss;

if (ptss_ip)
*ptss_ip = 0;
Expand Down Expand Up @@ -1177,8 +1179,13 @@ static u64 intel_pt_switch_ip(struct machine *machine, u64 *ptss_ip)
if (!switch_ip || !ptss_ip)
return 0;

if (pt->have_sched_switch == 1)
ptss = "perf_trace_sched_switch";
else
ptss = "__perf_event_task_sched_out";

for (sym = start; sym; sym = dso__next_symbol(sym)) {
if (!strcmp(sym->name, "perf_trace_sched_switch")) {
if (!strcmp(sym->name, ptss)) {
ip = map->unmap_ip(map, sym->start);
if (ip >= map->start && ip < map->end) {
*ptss_ip = ip;
Expand All @@ -1198,11 +1205,11 @@ static int intel_pt_run_decoder(struct intel_pt_queue *ptq, u64 *timestamp)

if (!pt->kernel_start) {
pt->kernel_start = machine__kernel_start(pt->machine);
if (pt->per_cpu_mmaps && pt->have_sched_switch &&
if (pt->per_cpu_mmaps &&
(pt->have_sched_switch == 1 || pt->have_sched_switch == 3) &&
!pt->timeless_decoding && intel_pt_tracing_kernel(pt) &&
!pt->sampling_mode) {
pt->switch_ip = intel_pt_switch_ip(pt->machine,
&pt->ptss_ip);
pt->switch_ip = intel_pt_switch_ip(pt, &pt->ptss_ip);
if (pt->switch_ip) {
intel_pt_log("switch_ip: %"PRIx64" ptss_ip: %"PRIx64"\n",
pt->switch_ip, pt->ptss_ip);
Expand Down Expand Up @@ -1387,31 +1394,18 @@ static struct intel_pt_queue *intel_pt_cpu_to_ptq(struct intel_pt *pt, int cpu)
return NULL;
}

static int intel_pt_process_switch(struct intel_pt *pt,
struct perf_sample *sample)
static int intel_pt_sync_switch(struct intel_pt *pt, int cpu, pid_t tid,
u64 timestamp)
{
struct intel_pt_queue *ptq;
struct perf_evsel *evsel;
pid_t tid;
int cpu, err;

evsel = perf_evlist__id2evsel(pt->session->evlist, sample->id);
if (evsel != pt->switch_evsel)
return 0;

tid = perf_evsel__intval(evsel, sample, "next_pid");
cpu = sample->cpu;

intel_pt_log("sched_switch: cpu %d tid %d time %"PRIu64" tsc %#"PRIx64"\n",
cpu, tid, sample->time, perf_time_to_tsc(sample->time,
&pt->tc));
int err;

if (!pt->sync_switch)
goto out;
return 1;

ptq = intel_pt_cpu_to_ptq(pt, cpu);
if (!ptq)
goto out;
return 1;

switch (ptq->switch_state) {
case INTEL_PT_SS_NOT_TRACING:
Expand All @@ -1424,7 +1418,7 @@ static int intel_pt_process_switch(struct intel_pt *pt,
return 0;
case INTEL_PT_SS_EXPECTING_SWITCH_EVENT:
if (!ptq->on_heap) {
ptq->timestamp = perf_time_to_tsc(sample->time,
ptq->timestamp = perf_time_to_tsc(timestamp,
&pt->tc);
err = auxtrace_heap__add(&pt->heap, ptq->queue_nr,
ptq->timestamp);
Expand All @@ -1441,10 +1435,76 @@ static int intel_pt_process_switch(struct intel_pt *pt,
default:
break;
}
out:

return 1;
}

static int intel_pt_process_switch(struct intel_pt *pt,
struct perf_sample *sample)
{
struct perf_evsel *evsel;
pid_t tid;
int cpu, ret;

evsel = perf_evlist__id2evsel(pt->session->evlist, sample->id);
if (evsel != pt->switch_evsel)
return 0;

tid = perf_evsel__intval(evsel, sample, "next_pid");
cpu = sample->cpu;

intel_pt_log("sched_switch: cpu %d tid %d time %"PRIu64" tsc %#"PRIx64"\n",
cpu, tid, sample->time, perf_time_to_tsc(sample->time,
&pt->tc));

ret = intel_pt_sync_switch(pt, cpu, tid, sample->time);
if (ret <= 0)
return ret;

return machine__set_current_tid(pt->machine, cpu, -1, tid);
}

static int intel_pt_context_switch(struct intel_pt *pt, union perf_event *event,
struct perf_sample *sample)
{
bool out = event->header.misc & PERF_RECORD_MISC_SWITCH_OUT;
pid_t pid, tid;
int cpu, ret;

cpu = sample->cpu;

if (pt->have_sched_switch == 3) {
if (!out)
return 0;
if (event->header.type != PERF_RECORD_SWITCH_CPU_WIDE) {
pr_err("Expecting CPU-wide context switch event\n");
return -EINVAL;
}
pid = event->context_switch.next_prev_pid;
tid = event->context_switch.next_prev_tid;
} else {
if (out)
return 0;
pid = sample->pid;
tid = sample->tid;
}

if (tid == -1) {
pr_err("context_switch event has no tid\n");
return -EINVAL;
}

intel_pt_log("context_switch: cpu %d pid %d tid %d time %"PRIu64" tsc %#"PRIx64"\n",
cpu, pid, tid, sample->time, perf_time_to_tsc(sample->time,
&pt->tc));

ret = intel_pt_sync_switch(pt, cpu, tid, sample->time);
if (ret <= 0)
return ret;

return machine__set_current_tid(pt->machine, cpu, pid, tid);
}

static int intel_pt_process_itrace_start(struct intel_pt *pt,
union perf_event *event,
struct perf_sample *sample)
Expand Down Expand Up @@ -1515,6 +1575,9 @@ static int intel_pt_process_event(struct perf_session *session,
err = intel_pt_process_switch(pt, sample);
else if (event->header.type == PERF_RECORD_ITRACE_START)
err = intel_pt_process_itrace_start(pt, event, sample);
else if (event->header.type == PERF_RECORD_SWITCH ||
event->header.type == PERF_RECORD_SWITCH_CPU_WIDE)
err = intel_pt_context_switch(pt, event, sample);

intel_pt_log("event %s (%u): cpu %d time %"PRIu64" tsc %#"PRIx64"\n",
perf_event__name(event->header.type), event->header.type,
Expand Down Expand Up @@ -1777,6 +1840,18 @@ static struct perf_evsel *intel_pt_find_sched_switch(struct perf_evlist *evlist)
return NULL;
}

static bool intel_pt_find_switch(struct perf_evlist *evlist)
{
struct perf_evsel *evsel;

evlist__for_each(evlist, evsel) {
if (evsel->attr.context_switch)
return true;
}

return false;
}

static const char * const intel_pt_info_fmts[] = {
[INTEL_PT_PMU_TYPE] = " PMU Type %"PRId64"\n",
[INTEL_PT_TIME_SHIFT] = " Time Shift %"PRIu64"\n",
Expand Down Expand Up @@ -1888,6 +1963,10 @@ int intel_pt_process_auxtrace_info(union perf_event *event,
pr_err("%s: missing sched_switch event\n", __func__);
goto err_delete_thread;
}
} else if (pt->have_sched_switch == 2 &&
!intel_pt_find_switch(session->evlist)) {
pr_err("%s: missing context_switch attribute flag\n", __func__);
goto err_delete_thread;
}

if (session->itrace_synth_opts && session->itrace_synth_opts->set) {
Expand Down

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