Messages in this thread | | | From | Arnaldo Carvalho de Melo <> | Date | Thu, 5 Mar 2020 20:17:44 -0300 | Subject | Re: [PATCH 02/12] perf tools: Support PERF_SAMPLE_BRANCH_HW_INDEX |
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Em Thu, Mar 05, 2020 at 04:02:10PM -0500, Liang, Kan escreveu: > > > On 3/5/2020 3:25 PM, Arnaldo Carvalho de Melo wrote: > > Em Fri, Feb 28, 2020 at 08:30:01AM -0800, kan.liang@linux.intel.com escreveu: > > > From: Kan Liang <kan.liang@linux.intel.com> > > > > > > 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. > > > > So while this works with a kernel where PERF_SAMPLE_BRANCH_HW_INDEX is > > present and we get, from the committer notes I was putting together > > while testing/applying this cset: > > > > 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. > > > > Cool, and look at that 'attr.precise_ip: 3' part, the kernel is OK with > > having that together with attr.branch_sample_type with HW_INDEX set. > > > > The problem happens when I go test this in an older kernel, where the > > kernel doesn't know about HW_INDEX, we get it disabled but then > > precise_ip is set to zero in its detection , even if at the end we get > > it to 3, as expected, which got me a bit confused, I'll investigate this > > a bit more to try and avoid these extra probes for the max precise level > > that fails in older kernels due to branch_sample_type having HW_INDEX > > :-\ > > It looks like this is an expected behavior for the event with maximum > precise config for current perf tool. > > The related commits are as below: > commit ID: 4e8a5c155137 ("perf evsel: Fix max perf_event_attr.precise_ip > detection") > commit ID: cd136189370c ("perf evsel: Do not rely on errno values for > precise_ip fallback") > > Before handling any standard fallback (not just HW_INDEX), perf tool will > try all the precise_ip value first.
Right, and since it uses HW_INDEX and the kernel doesn't support that, that precise_ip max value detection will fail, it will go back to whatever it was and try again later, then the fallback will remove the HW_INDEX and it will work.
What I said is that if we don't set branch_sample_type when detecting the max precise_ip, then that detection will work and we will not needlessly go on testing with precise_ip = 3, 2, 1, 0.
My doubt was more about if HW_INDEX (or any other branch_sample_type) had to be tested in conjunction with precise_ip, which I think isn't the case from what I saw in my tests.
- Arnaldo
> Thanks, > Kan > > > > > > > # perf record -vv --call-graph lbr -a sleep 5 > > <SNIP> > > ------------------------------------------------------------ > > perf_event_attr: > > 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 > > ------------------------------------------------------------ > > sys_perf_event_open: pid -1 cpu 0 group_fd -1 flags 0x8 > > sys_perf_event_open failed, error -95 > > decreasing precise_ip by one (2) > > ------------------------------------------------------------ > > perf_event_attr: > > 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 2 > > 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 > > ------------------------------------------------------------ > > sys_perf_event_open: pid -1 cpu 0 group_fd -1 flags 0x8 > > sys_perf_event_open failed, error -95 > > decreasing precise_ip by one (1) > > ------------------------------------------------------------ > > perf_event_attr: > > 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 1 > > 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 > > ------------------------------------------------------------ > > sys_perf_event_open: pid -1 cpu 0 group_fd -1 flags 0x8 > > sys_perf_event_open failed, error -95 > > decreasing precise_ip by one (0) > > ------------------------------------------------------------ > > perf_event_attr: > > 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 > > 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 > > ------------------------------------------------------------ > > sys_perf_event_open: pid -1 cpu 0 group_fd -1 flags 0x8 > > sys_perf_event_open failed, error -22 > > switching off branch HW index support > > ------------------------------------------------------------ > > perf_event_attr: > > 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 > > ------------------------------------------------------------ > > > > > > > Signed-off-by: Kan Liang <kan.liang@linux.intel.com> > > > --- > > > tools/perf/util/evsel.c | 15 ++++++++++++--- > > > tools/perf/util/evsel.h | 1 + > > > tools/perf/util/perf_event_attr_fprintf.c | 1 + > > > 3 files changed, 14 insertions(+), 3 deletions(-) > > > > > > diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c > > > index 05883a45de5b..816d930d774e 100644 > > > --- 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 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus, > > > 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 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus, > > > * 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 99a0cb60c556..33804740e2ca 100644 > > > --- 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 651203126c71..355d3458d4e6 100644 > > > --- 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 > > > -- > > > 2.17.1 > > > > >
--
- Arnaldo
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