perf evsel: Support PERF_SAMPLE_BRANCH_HW_INDEX

A new branch sample type PERF_SAMPLE_BRANCH_HW_INDEX has been introduced
in latest kernel.

Enable HW_INDEX by default in LBR call stack mode.

If kernel doesn't support the sample type, switching it off.

Add HW_INDEX in attr_fprintf as well. User can check whether the branch
sample type is set via debug information or header.

Committer testing:

First collect some samples with LBR callchains, system wide, for a few
seconds:

  # perf record --call-graph lbr -a sleep 5
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.625 MB perf.data (224 samples) ]
  #

Now lets use 'perf evlist -v' to look at the branch_sample_type:

  # perf evlist -v
  cycles: size: 120, { sample_period, sample_freq }: 4000, sample_type: IP|TID|TIME|CALLCHAIN|CPU|PERIOD|BRANCH_STACK, read_format: ID, disabled: 1, inherit: 1, mmap: 1, comm: 1, freq: 1, task: 1, precise_ip: 3, sample_id_all: 1, exclude_guest: 1, mmap2: 1, comm_exec: 1, ksymbol: 1, bpf_event: 1, branch_sample_type: USER|CALL_STACK|NO_FLAGS|NO_CYCLES|HW_INDEX
  #

So the machine has the kernel feature, and it was correctly added to
perf_event_attr.branch_sample_type, for the default 'cycles' event.

If we do it in another machine, where the kernel lacks the HW_INDEX
feature, we get:

  # perf record --call-graph lbr -a sleep 2s
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 1.690 MB perf.data (499 samples) ]
  # perf evlist -v
  cycles: size: 120, { sample_period, sample_freq }: 4000, sample_type: IP|TID|TIME|CALLCHAIN|CPU|PERIOD|BRANCH_STACK, read_format: ID, disabled: 1, inherit: 1, mmap: 1, comm: 1, freq: 1, task: 1, precise_ip: 3, sample_id_all: 1, exclude_guest: 1, mmap2: 1, comm_exec: 1, ksymbol: 1, bpf_event: 1, branch_sample_type: USER|CALL_STACK|NO_FLAGS|NO_CYCLES
  #

No HW_INDEX in attr.branch_sample_type.

Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexey Budankov <alexey.budankov@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Pavel Gerasimov <pavel.gerasimov@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Vitaly Slobodskoy <vitaly.slobodskoy@intel.com>
Link: http://lore.kernel.org/lkml/20200228163011.19358-3-kan.liang@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 05883a4..816d930 100644 (file)
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -712,7 +712,8 @@ static void __perf_evsel__config_callchain(struct evsel *evsel,
                                attr->branch_sample_type = PERF_SAMPLE_BRANCH_USER |
                                                        PERF_SAMPLE_BRANCH_CALL_STACK |
                                                        PERF_SAMPLE_BRANCH_NO_CYCLES |
-                                                       PERF_SAMPLE_BRANCH_NO_FLAGS;
+                                                       PERF_SAMPLE_BRANCH_NO_FLAGS |
+                                                       PERF_SAMPLE_BRANCH_HW_INDEX;
                        }
                } else
                         pr_warning("Cannot use LBR callstack with branch stack. "
@@ -763,7 +764,8 @@ perf_evsel__reset_callgraph(struct evsel *evsel,
        if (param->record_mode == CALLCHAIN_LBR) {
                perf_evsel__reset_sample_bit(evsel, BRANCH_STACK);
                attr->branch_sample_type &= ~(PERF_SAMPLE_BRANCH_USER |
-                                             PERF_SAMPLE_BRANCH_CALL_STACK);
+                                             PERF_SAMPLE_BRANCH_CALL_STACK |
+                                             PERF_SAMPLE_BRANCH_HW_INDEX);
        }
        if (param->record_mode == CALLCHAIN_DWARF) {
                perf_evsel__reset_sample_bit(evsel, REGS_USER);
@@ -1673,6 +1675,8 @@ fallback_missing_features:
                evsel->core.attr.ksymbol = 0;
        if (perf_missing_features.bpf)
                evsel->core.attr.bpf_event = 0;
+       if (perf_missing_features.branch_hw_idx)
+               evsel->core.attr.branch_sample_type &= ~PERF_SAMPLE_BRANCH_HW_INDEX;
 retry_sample_id:
        if (perf_missing_features.sample_id_all)
                evsel->core.attr.sample_id_all = 0;
@@ -1784,7 +1788,12 @@ try_fallback:
         * Must probe features in the order they were added to the
         * perf_event_attr interface.
         */
-       if (!perf_missing_features.aux_output && evsel->core.attr.aux_output) {
+       if (!perf_missing_features.branch_hw_idx &&
+           (evsel->core.attr.branch_sample_type & PERF_SAMPLE_BRANCH_HW_INDEX)) {
+               perf_missing_features.branch_hw_idx = true;
+               pr_debug2("switching off branch HW index support\n");
+               goto fallback_missing_features;
+       } else if (!perf_missing_features.aux_output && evsel->core.attr.aux_output) {
                perf_missing_features.aux_output = true;
                pr_debug2_peo("Kernel has no attr.aux_output support, bailing out\n");
                goto out_close;

diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
index 99a0cb6..3380474 100644 (file)
--- a/tools/perf/util/evsel.h
+++ b/tools/perf/util/evsel.h
@@ -119,6 +119,7 @@ struct perf_missing_features {
        bool ksymbol;
        bool bpf;
        bool aux_output;
+       bool branch_hw_idx;
 };
 
 extern struct perf_missing_features perf_missing_features;

diff --git a/tools/perf/util/perf_event_attr_fprintf.c b/tools/perf/util/perf_event_attr_fprintf.c
index 6512031..355d345 100644 (file)
--- a/tools/perf/util/perf_event_attr_fprintf.c
+++ b/tools/perf/util/perf_event_attr_fprintf.c
@@ -50,6 +50,7 @@ static void __p_branch_sample_type(char *buf, size_t size, u64 value)
                bit_name(ABORT_TX), bit_name(IN_TX), bit_name(NO_TX),
                bit_name(COND), bit_name(CALL_STACK), bit_name(IND_JUMP),
                bit_name(CALL), bit_name(NO_FLAGS), bit_name(NO_CYCLES),
+               bit_name(HW_INDEX),
                { .name = NULL, }
        };
 #undef bit_name