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Date: Wed, 2 Sep 2015 16:09:47 +0300
From: Adrian Hunter <adrian.hunter@...el.com>
To: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: linux-kernel@...r.kernel.org, Jiri Olsa <jolsa@...hat.com>
Subject: Re: [PATCH 2/2] perf tools: Add support for PERF_RECORD_SWITCH to
Intel PT
On 13/08/15 12:40, Adrian Hunter wrote:
> 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@...el.com>
This one still applies.
> ---
> tools/perf/arch/x86/util/intel-pt.c | 55 ++++++++++++---
> tools/perf/util/intel-pt.c | 129 +++++++++++++++++++++++++++++-------
> 2 files changed, 151 insertions(+), 33 deletions(-)
>
> diff --git a/tools/perf/arch/x86/util/intel-pt.c b/tools/perf/arch/x86/util/intel-pt.c
> index 2ca10d796c0b..b02af064f0f9 100644
> --- a/tools/perf/arch/x86/util/intel-pt.c
> +++ b/tools/perf/arch/x86/util/intel-pt.c
> @@ -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) {
> @@ -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);
> + }
> }
>
> /*
> diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c
> index 4bae958096d4..1f6aab58e931 100644
> --- a/tools/perf/util/intel-pt.c
> +++ b/tools/perf/util/intel-pt.c
> @@ -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;
> @@ -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;
> @@ -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);
> @@ -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:
> @@ -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);
> @@ -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)
> @@ -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,
> @@ -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",
> @@ -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) {
>
--
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