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While 'perf sched latency' reports task runtime and delay statistics
(average and maximum delay), it does not provide a visual representation
of how task wait times are distributed across latency ranges between
snapshots (start and finish of the analysis window).
The --histogram option collects CPU wait latencies (time between when
a task becomes runnable and when it gets scheduled onto a CPU) into 22
latency buckets, displaying an ASCII bar chart distribution.
The --hist-mode option configures the bucketing scheme:
- log (default). Logarithmic latency buckets ranging from
sub-microsecond (< 1 us) up to >= 1.05 seconds
- linear. Equal-width linear latency buckets
(i.e., 100 us steps up to >= 2.1 ms)
The --time option allows filtering trace event processing to a
specific time interval [start,stop].
Example histogram output excerpt:
❯ sudo perf sched latency --histogram --CPU 0
CPU Wait Latency Distribution Histogram (between snapshots) (total samples: 36114)
-------------------------------------------------------------------
Latency Range | Count | Pct | Histogram Graph
-------------------------------------------------------------------
< 1 us | 17 | 0.0% | #
2 - 4 us | 673 | 1.9% | #
4 - 8 us | 6237 | 17.3% | ######
8 - 16 us | 3224 | 8.9% | ###
16 - 32 us | 1388 | 3.8% | #
32 - 64 us | 709 | 2.0% | #
64 - 128 us | 690 | 1.9% | #
128 - 256 us | 789 | 2.2% | #
256 - 512 us | 541 | 1.5% | #
512 - 1024 us | 2256 | 6.2% | ##
1 - 2 ms | 3577 | 9.9% | ###
2 - 4 ms | 13259 | 36.7% | ##############
4 - 8 ms | 2523 | 7.0% | ##
8 - 16 ms | 222 | 0.6% | #
16 - 32 ms | 10 | 0.0% | #
>= 1.05 s | 3 | 0.0% | #
-------------------------------------------------------------------
Reviewed-by: Ian Rogers <irogers@google.com>
Signed-off-by: Aaron Tomlin <atomlin@atomlin.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
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| .. | ||
| attr | ||
| base_probe | ||
| base_report | ||
| common | ||
| coresight | ||
| lib | ||
| addr2line_inlines.sh | ||
| amd-ibs-swfilt.sh | ||
| annotate.sh | ||
| attr.sh | ||
| buildid.sh | ||
| c2c.sh | ||
| daemon.sh | ||
| data_file_offset_diagnostics.sh | ||
| data_type_profiling.sh | ||
| data_validation.sh | ||
| diff.sh | ||
| drm_pmu.sh | ||
| evlist.sh | ||
| ftrace.sh | ||
| header.sh | ||
| inject_aslr.sh | ||
| inject-callchain.sh | ||
| jitdump-python.sh | ||
| kallsyms.sh | ||
| kvm.sh | ||
| kwork.sh | ||
| list.sh | ||
| lock_contention.sh | ||
| perf_sched_stats.sh | ||
| perf-report-hierarchy.sh | ||
| perftool-testsuite_probe.sh | ||
| perftool-testsuite_report.sh | ||
| pipe_test.sh | ||
| probe_vfs_getname.sh | ||
| python-use.sh | ||
| record_bpf_filter.sh | ||
| record_lbr.sh | ||
| record_offcpu.sh | ||
| record_sideband.sh | ||
| record_weak_term.sh | ||
| record.sh | ||
| record+probe_libc_inet_pton.sh | ||
| record+script_probe_vfs_getname.sh | ||
| record+zstd_comp_decomp_multi_record.sh | ||
| record+zstd_comp_decomp.sh | ||
| sched.sh | ||
| script_dlfilter.sh | ||
| script_perl.sh | ||
| script_python.sh | ||
| script.sh | ||
| stat_all_metricgroups.sh | ||
| stat_all_metrics.sh | ||
| stat_all_pfm.sh | ||
| stat_all_pmu.sh | ||
| stat_bpf_counters_cgrp.sh | ||
| stat_bpf_counters.sh | ||
| stat_metrics_cgrp.sh | ||
| stat_metrics_values.sh | ||
| stat.sh | ||
| stat+csv_output.sh | ||
| stat+csv_summary.sh | ||
| stat+event_uniquifying.sh | ||
| stat+json_output.sh | ||
| stat+shadow_stat.sh | ||
| stat+std_output.sh | ||
| test_arm_callgraph_fp.sh | ||
| test_arm_spe_fork.sh | ||
| test_arm_spe.sh | ||
| test_bpf_metadata.sh | ||
| test_brstack.sh | ||
| test_data_symbol.sh | ||
| test_dwarf_unwind_multithreaded.sh | ||
| test_event_open_fallback.sh | ||
| test_intel_pt.sh | ||
| test_java_symbol.sh | ||
| test_perf_data_converter_ctf.sh | ||
| test_perf_data_converter_json.sh | ||
| test_stat_intel_tpebs.sh | ||
| test_task_analyzer.sh | ||
| test_test_junit_output.sh | ||
| test_uprobe_from_different_cu.sh | ||
| timechart.sh | ||
| top.sh | ||
| trace_btf_enum.sh | ||
| trace_btf_general.sh | ||
| trace_exit_race.sh | ||
| trace_record_replay.sh | ||
| trace_summary.sh | ||
| trace+probe_vfs_getname.sh | ||