Re: [PATCH V5 8/8] perf tools: Add branch counter knob

From: Liang, Kan
Date: Thu Oct 26 2023 - 14:29:10 EST

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On 2023-10-25 10:12 p.m., Ian Rogers wrote:
> On Wed, Oct 25, 2023 at 1:16 PM <kan.liang@xxxxxxxxxxxxxxx> wrote:
>>
>> From: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
>>
>> Add a new branch filter, "counter", for the branch counter option. It is
>> used to mark the events which should be logged in the branch. If it is
>> applied with the -j option, the counters of all the events should be
>> logged in the branch. If the legacy kernel doesn't support the new
>> branch sample type, switching off the branch counter filter.
>>
>> The stored counter values in each branch are displayed right after the
>> regular branch stack information via perf report -D.
>>
>> Usage examples:
>>
>> perf record -e "{branch-instructions,branch-misses}:S" -j any,counter
>>
>> Only the first event, branch-instructions, collect the LBR. Both
>> branch-instructions and branch-misses are marked as logged events.
>> The occurrences information of them can be found in the branch stack
>> extension space of each branch.
>>
>> perf record -e "{cpu/branch-instructions,branch_type=any/,
>> cpu/branch-misses,branch_type=counter/}"
>>
>> Only the first event, branch-instructions, collect the LBR. Only the
>> branch-misses event is marked as a logged event.
>>
>> Signed-off-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
>
> Reviewed-by: Ian Rogers <irogers@xxxxxxxxxx>

Thanks Ian for the review.

>
> Perhaps add a test somewhere like:
> https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/tests/shell/record.sh
> for coverage when hardware supports the feature.

Sure, I will add a test when posting the perf tool patches.

Thanks,
Kan
>
> Thanks,
> Ian
>
>> ---
>>
>> No changes since V4
>>
>> tools/perf/Documentation/perf-record.txt | 4 +++
>> tools/perf/util/evsel.c | 31 ++++++++++++++++++++++-
>> tools/perf/util/evsel.h | 1 +
>> tools/perf/util/parse-branch-options.c | 1 +
>> tools/perf/util/perf_event_attr_fprintf.c | 1 +
>> tools/perf/util/sample.h | 1 +
>> tools/perf/util/session.c | 15 +++++++++--
>> 7 files changed, 51 insertions(+), 3 deletions(-)
>>
>> diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
>> index d5217be012d7..b6afe7cc948d 100644
>> --- a/tools/perf/Documentation/perf-record.txt
>> +++ b/tools/perf/Documentation/perf-record.txt
>> @@ -442,6 +442,10 @@ following filters are defined:
>> 4th-Gen Xeon+ server), the save branch type is unconditionally enabled
>> when the taken branch stack sampling is enabled.
>> - priv: save privilege state during sampling in case binary is not available later
>> + - counter: save occurrences of the event since the last branch entry. Currently, the
>> + feature is only supported by a newer CPU, e.g., Intel Sierra Forest and
>> + later platforms. An error out is expected if it's used on the unsupported
>> + kernel or CPUs.
>>
>> +
>> The option requires at least one branch type among any, any_call, any_ret, ind_call, cond.
>> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
>> index a8a5ff87cc1f..58a9b8c82790 100644
>> --- a/tools/perf/util/evsel.c
>> +++ b/tools/perf/util/evsel.c
>> @@ -1831,6 +1831,8 @@ static int __evsel__prepare_open(struct evsel *evsel, struct perf_cpu_map *cpus,
>>
>> static void evsel__disable_missing_features(struct evsel *evsel)
>> {
>> + if (perf_missing_features.branch_counters)
>> + evsel->core.attr.branch_sample_type &= ~PERF_SAMPLE_BRANCH_COUNTERS;
>> if (perf_missing_features.read_lost)
>> evsel->core.attr.read_format &= ~PERF_FORMAT_LOST;
>> if (perf_missing_features.weight_struct) {
>> @@ -1884,7 +1886,12 @@ bool evsel__detect_missing_features(struct evsel *evsel)
>> * Must probe features in the order they were added to the
>> * perf_event_attr interface.
>> */
>> - if (!perf_missing_features.read_lost &&
>> + if (!perf_missing_features.branch_counters &&
>> + (evsel->core.attr.branch_sample_type & PERF_SAMPLE_BRANCH_COUNTERS)) {
>> + perf_missing_features.branch_counters = true;
>> + pr_debug2("switching off branch counters support\n");
>> + return true;
>> + } else if (!perf_missing_features.read_lost &&
>> (evsel->core.attr.read_format & PERF_FORMAT_LOST)) {
>> perf_missing_features.read_lost = true;
>> pr_debug2("switching off PERF_FORMAT_LOST support\n");
>> @@ -2344,6 +2351,18 @@ u64 evsel__bitfield_swap_branch_flags(u64 value)
>> return new_val;
>> }
>>
>> +static inline bool evsel__has_branch_counters(const struct evsel *evsel)
>> +{
>> + struct evsel *cur, *leader = evsel__leader(evsel);
>> +
>> + evlist__for_each_entry(evsel->evlist, cur) {
>> + if ((leader == evsel__leader(cur)) &&
>> + (cur->core.attr.branch_sample_type & PERF_SAMPLE_BRANCH_COUNTERS))
>> + return true;
>> + }
>> + return false;
>> +}
>> +
>> int evsel__parse_sample(struct evsel *evsel, union perf_event *event,
>> struct perf_sample *data)
>> {
>> @@ -2577,6 +2596,16 @@ int evsel__parse_sample(struct evsel *evsel, union perf_event *event,
>>
>> OVERFLOW_CHECK(array, sz, max_size);
>> array = (void *)array + sz;
>> +
>> + if (evsel__has_branch_counters(evsel)) {
>> + OVERFLOW_CHECK_u64(array);
>> +
>> + data->branch_stack_cntr = (u64 *)array;
>> + sz = data->branch_stack->nr * sizeof(u64);
>> +
>> + OVERFLOW_CHECK(array, sz, max_size);
>> + array = (void *)array + sz;
>> + }
>> }
>>
>> if (type & PERF_SAMPLE_REGS_USER) {
>> diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
>> index 848534ec74fa..85f24c986392 100644
>> --- a/tools/perf/util/evsel.h
>> +++ b/tools/perf/util/evsel.h
>> @@ -191,6 +191,7 @@ struct perf_missing_features {
>> bool code_page_size;
>> bool weight_struct;
>> bool read_lost;
>> + bool branch_counters;
>> };
>>
>> extern struct perf_missing_features perf_missing_features;
>> diff --git a/tools/perf/util/parse-branch-options.c b/tools/perf/util/parse-branch-options.c
>> index fd67d204d720..f7f7aff3d85a 100644
>> --- a/tools/perf/util/parse-branch-options.c
>> +++ b/tools/perf/util/parse-branch-options.c
>> @@ -36,6 +36,7 @@ static const struct branch_mode branch_modes[] = {
>> BRANCH_OPT("stack", PERF_SAMPLE_BRANCH_CALL_STACK),
>> BRANCH_OPT("hw_index", PERF_SAMPLE_BRANCH_HW_INDEX),
>> BRANCH_OPT("priv", PERF_SAMPLE_BRANCH_PRIV_SAVE),
>> + BRANCH_OPT("counter", PERF_SAMPLE_BRANCH_COUNTERS),
>> BRANCH_END
>> };
>>
>> diff --git a/tools/perf/util/perf_event_attr_fprintf.c b/tools/perf/util/perf_event_attr_fprintf.c
>> index 2247991451f3..8f04d3b7f3ec 100644
>> --- a/tools/perf/util/perf_event_attr_fprintf.c
>> +++ b/tools/perf/util/perf_event_attr_fprintf.c
>> @@ -55,6 +55,7 @@ static void __p_branch_sample_type(char *buf, size_t size, u64 value)
>> bit_name(COND), bit_name(CALL_STACK), bit_name(IND_JUMP),
>> bit_name(CALL), bit_name(NO_FLAGS), bit_name(NO_CYCLES),
>> bit_name(TYPE_SAVE), bit_name(HW_INDEX), bit_name(PRIV_SAVE),
>> + bit_name(COUNTERS),
>> { .name = NULL, }
>> };
>> #undef bit_name
>> diff --git a/tools/perf/util/sample.h b/tools/perf/util/sample.h
>> index c92ad0f51ecd..70b2c3135555 100644
>> --- a/tools/perf/util/sample.h
>> +++ b/tools/perf/util/sample.h
>> @@ -113,6 +113,7 @@ struct perf_sample {
>> void *raw_data;
>> struct ip_callchain *callchain;
>> struct branch_stack *branch_stack;
>> + u64 *branch_stack_cntr;
>> struct regs_dump user_regs;
>> struct regs_dump intr_regs;
>> struct stack_dump user_stack;
>> diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
>> index 1e9aa8ed15b6..4a094ab0362b 100644
>> --- a/tools/perf/util/session.c
>> +++ b/tools/perf/util/session.c
>> @@ -1150,9 +1150,13 @@ static void callchain__printf(struct evsel *evsel,
>> i, callchain->ips[i]);
>> }
>>
>> -static void branch_stack__printf(struct perf_sample *sample, bool callstack)
>> +static void branch_stack__printf(struct perf_sample *sample,
>> + struct evsel *evsel)
>> {
>> struct branch_entry *entries = perf_sample__branch_entries(sample);
>> + bool callstack = evsel__has_branch_callstack(evsel);
>> + u64 *branch_stack_cntr = sample->branch_stack_cntr;
>> + struct perf_env *env = evsel__env(evsel);
>> uint64_t i;
>>
>> if (!callstack) {
>> @@ -1194,6 +1198,13 @@ static void branch_stack__printf(struct perf_sample *sample, bool callstack)
>> }
>> }
>> }
>> +
>> + if (branch_stack_cntr) {
>> + printf("... branch stack counters: nr:%" PRIu64 " (counter width: %u max counter nr:%u)\n",
>> + sample->branch_stack->nr, env->br_cntr_width, env->br_cntr_nr);
>> + for (i = 0; i < sample->branch_stack->nr; i++)
>> + printf("..... %2"PRIu64": %016" PRIx64 "\n", i, branch_stack_cntr[i]);
>> + }
>> }
>>
>> static void regs_dump__printf(u64 mask, u64 *regs, const char *arch)
>> @@ -1355,7 +1366,7 @@ static void dump_sample(struct evsel *evsel, union perf_event *event,
>> callchain__printf(evsel, sample);
>>
>> if (evsel__has_br_stack(evsel))
>> - branch_stack__printf(sample, evsel__has_branch_callstack(evsel));
>> + branch_stack__printf(sample, evsel);
>>
>> if (sample_type & PERF_SAMPLE_REGS_USER)
>> regs_user__printf(sample, arch);
>> --
>> 2.35.1
>>

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Previous message: Jason Gunthorpe: "Re: [PATCH v8 0/8] Add Intel VT-d nested translation (part 1/2)"
In reply to: Ian Rogers: "Re: [PATCH V5 8/8] perf tools: Add branch counter knob"
Next in thread: kan . liang: "[PATCH V5 5/8] perf/x86/intel: Support branch counters logging"
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