Re: [PATCH 11/16] perf intel-pt: Add support for synthesizing callchains for regular events

From: Arnaldo Carvalho de Melo
Date: Thu Apr 16 2020 - 11:15:01 EST

Em Wed, Apr 01, 2020 at 01:16:08PM +0300, Adrian Hunter escreveu:
> Currently, callchains can be synthesized only for synthesized events.
> Support also synthesizing callchains for regular events.

This is super cool, I wonder if we shouldn't do it automatically or just
adding a new type of callchains, i.e.:

perf record --call-graph pt uname

Should take care of all the details, i.e. do the extra steps below
behind the scenes.

Possibly even find out that the workload specified was built with
-fomit-frame-pointers, that the hardware has Intel PT and do all behind
the scenes for:

perf record -g uname

Alternatively we could take some less seemingly far fetched approach and
make this configurable via:

perf config call-graph.record-mode=pt

What do you think?

- Arnaldo

> Example:
>
> # perf record --kcore --aux-sample -e '{intel_pt//,cycles}' -c 10000 uname
> Linux
> [ perf record: Woken up 3 times to write data ]
> [ perf record: Captured and wrote 0.532 MB perf.data ]
> # perf script --itrace=Ge | head -20
> uname 4864 2419025.358181: 10000 cycles:
> ffffffffbba56965 apparmor_bprm_committing_creds+0x35 ([kernel.kallsyms])
> ffffffffbc400cd5 __indirect_thunk_start+0x5 ([kernel.kallsyms])
> ffffffffbba07422 security_bprm_committing_creds+0x22 ([kernel.kallsyms])
> ffffffffbb89805d install_exec_creds+0xd ([kernel.kallsyms])
> ffffffffbb90d9ac load_elf_binary+0x3ac ([kernel.kallsyms])
>
> uname 4864 2419025.358185: 10000 cycles:
> ffffffffbba56db0 apparmor_bprm_committed_creds+0x20 ([kernel.kallsyms])
> ffffffffbc400cd5 __indirect_thunk_start+0x5 ([kernel.kallsyms])
> ffffffffbba07452 security_bprm_committed_creds+0x22 ([kernel.kallsyms])
> ffffffffbb89809a install_exec_creds+0x4a ([kernel.kallsyms])
> ffffffffbb90d9ac load_elf_binary+0x3ac ([kernel.kallsyms])
>
> uname 4864 2419025.358189: 10000 cycles:
> ffffffffbb86fdf6 vma_adjust_trans_huge+0x6 ([kernel.kallsyms])
> ffffffffbb821660 __vma_adjust+0x160 ([kernel.kallsyms])
> ffffffffbb897be7 shift_arg_pages+0x97 ([kernel.kallsyms])
> ffffffffbb897ed9 setup_arg_pages+0x1e9 ([kernel.kallsyms])
> ffffffffbb90d9f2 load_elf_binary+0x3f2 ([kernel.kallsyms])
>
> Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
> ---
> tools/perf/util/intel-pt.c | 68 ++++++++++++++++++++++++++++++++++----
> 1 file changed, 61 insertions(+), 7 deletions(-)
>
> diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c
> index db25c77d82f3..a659b4a1b3f2 100644
> --- a/tools/perf/util/intel-pt.c
> +++ b/tools/perf/util/intel-pt.c
> @@ -124,6 +124,8 @@ struct intel_pt {
>
> struct range *time_ranges;
> unsigned int range_cnt;
> +
> + struct ip_callchain *chain;
> };
>
> enum switch_state {
> @@ -868,6 +870,45 @@ static u64 intel_pt_ns_to_ticks(const struct intel_pt *pt, u64 ns)
> pt->tc.time_mult;
> }
>
> +static struct ip_callchain *intel_pt_alloc_chain(struct intel_pt *pt)
> +{
> + size_t sz = sizeof(struct ip_callchain);
> +
> + /* Add 1 to callchain_sz for callchain context */
> + sz += (pt->synth_opts.callchain_sz + 1) * sizeof(u64);
> + return zalloc(sz);
> +}
> +
> +static int intel_pt_callchain_init(struct intel_pt *pt)
> +{
> + struct evsel *evsel;
> +
> + evlist__for_each_entry(pt->session->evlist, evsel) {
> + if (!(evsel->core.attr.sample_type & PERF_SAMPLE_CALLCHAIN))
> + evsel->synth_sample_type |= PERF_SAMPLE_CALLCHAIN;
> + }
> +
> + pt->chain = intel_pt_alloc_chain(pt);
> + if (!pt->chain)
> + return -ENOMEM;
> +
> + return 0;
> +}
> +
> +static void intel_pt_add_callchain(struct intel_pt *pt,
> + struct perf_sample *sample)
> +{
> + struct thread *thread = machine__findnew_thread(pt->machine,
> + sample->pid,
> + sample->tid);
> +
> + thread_stack__sample_late(thread, sample->cpu, pt->chain,
> + pt->synth_opts.callchain_sz + 1, sample->ip,
> + pt->kernel_start);
> +
> + sample->callchain = pt->chain;
> +}
> +
> static struct intel_pt_queue *intel_pt_alloc_queue(struct intel_pt *pt,
> unsigned int queue_nr)
> {
> @@ -880,11 +921,7 @@ static struct intel_pt_queue *intel_pt_alloc_queue(struct intel_pt *pt,
> return NULL;
>
> if (pt->synth_opts.callchain) {
> - size_t sz = sizeof(struct ip_callchain);
> -
> - /* Add 1 to callchain_sz for callchain context */
> - sz += (pt->synth_opts.callchain_sz + 1) * sizeof(u64);
> - ptq->chain = zalloc(sz);
> + ptq->chain = intel_pt_alloc_chain(pt);
> if (!ptq->chain)
> goto out_free;
> }
> @@ -1992,7 +2029,8 @@ static int intel_pt_sample(struct intel_pt_queue *ptq)
> if (!(state->type & INTEL_PT_BRANCH))
> return 0;
>
> - if (pt->synth_opts.callchain || pt->synth_opts.thread_stack)
> + if (pt->synth_opts.callchain || pt->synth_opts.add_callchain ||
> + pt->synth_opts.thread_stack)
> thread_stack__event(ptq->thread, ptq->cpu, ptq->flags, state->from_ip,
> state->to_ip, ptq->insn_len,
> state->trace_nr);
> @@ -2639,6 +2677,11 @@ static int intel_pt_process_event(struct perf_session *session,
> if (err)
> return err;
>
> + if (event->header.type == PERF_RECORD_SAMPLE) {
> + if (pt->synth_opts.add_callchain && !sample->callchain)
> + intel_pt_add_callchain(pt, sample);
> + }
> +
> if (event->header.type == PERF_RECORD_AUX &&
> (event->aux.flags & PERF_AUX_FLAG_TRUNCATED) &&
> pt->synth_opts.errors) {
> @@ -2710,6 +2753,7 @@ static void intel_pt_free(struct perf_session *session)
> session->auxtrace = NULL;
> thread__put(pt->unknown_thread);
> addr_filters__exit(&pt->filts);
> + zfree(&pt->chain);
> zfree(&pt->filter);
> zfree(&pt->time_ranges);
> free(pt);
> @@ -3348,6 +3392,7 @@ int intel_pt_process_auxtrace_info(union perf_event *event,
> !session->itrace_synth_opts->inject) {
> pt->synth_opts.branches = false;
> pt->synth_opts.callchain = true;
> + pt->synth_opts.add_callchain = true;
> }
> pt->synth_opts.thread_stack =
> session->itrace_synth_opts->thread_stack;
> @@ -3380,14 +3425,22 @@ int intel_pt_process_auxtrace_info(union perf_event *event,
> pt->branches_filter |= PERF_IP_FLAG_RETURN |
> PERF_IP_FLAG_TRACE_BEGIN;
>
> - if (pt->synth_opts.callchain && !symbol_conf.use_callchain) {
> + if ((pt->synth_opts.callchain || pt->synth_opts.add_callchain) &&
> + !symbol_conf.use_callchain) {
> symbol_conf.use_callchain = true;
> if (callchain_register_param(&callchain_param) < 0) {
> symbol_conf.use_callchain = false;
> pt->synth_opts.callchain = false;
> + pt->synth_opts.add_callchain = false;
> }
> }
>
> + if (pt->synth_opts.add_callchain) {
> + err = intel_pt_callchain_init(pt);
> + if (err)
> + goto err_delete_thread;
> + }
> +
> err = intel_pt_synth_events(pt, session);
> if (err)
> goto err_delete_thread;
> @@ -3410,6 +3463,7 @@ int intel_pt_process_auxtrace_info(union perf_event *event,
> return 0;
>
> err_delete_thread:
> + zfree(&pt->chain);
> thread__zput(pt->unknown_thread);
> err_free_queues:
> intel_pt_log_disable();
> --
> 2.17.1
>

--

- Arnaldo