diff options
Diffstat (limited to 'tools/perf/Documentation/perf-stat.txt')
| -rw-r--r-- | tools/perf/Documentation/perf-stat.txt | 27 |
1 files changed, 15 insertions, 12 deletions
diff --git a/tools/perf/Documentation/perf-stat.txt b/tools/perf/Documentation/perf-stat.txt index 18abdc1dce05..29bdcfa93f04 100644 --- a/tools/perf/Documentation/perf-stat.txt +++ b/tools/perf/Documentation/perf-stat.txt @@ -394,10 +394,10 @@ See perf list output for the possible metrics and metricgroups. Do not aggregate counts across all monitored CPUs. --topdown:: -Print complete top-down metrics supported by the CPU. This allows to -determine bottle necks in the CPU pipeline for CPU bound workloads, -by breaking the cycles consumed down into frontend bound, backend bound, -bad speculation and retiring. +Print top-down metrics supported by the CPU. This allows to determine +bottle necks in the CPU pipeline for CPU bound workloads, by breaking +the cycles consumed down into frontend bound, backend bound, bad +speculation and retiring. Frontend bound means that the CPU cannot fetch and decode instructions fast enough. Backend bound means that computation or memory access is the bottle @@ -430,15 +430,18 @@ CPUs the workload runs on. If needed the CPUs can be forced using taskset. --td-level:: -Print the top-down statistics that equal to or lower than the input level. -It allows users to print the interested top-down metrics level instead of -the complete top-down metrics. +Print the top-down statistics that equal the input level. It allows +users to print the interested top-down metrics level instead of the +level 1 top-down metrics. + +As the higher levels gather more metrics and use more counters they +will be less accurate. By convention a metric can be examined by +appending '_group' to it and this will increase accuracy compared to +gathering all metrics for a level. For example, level 1 analysis may +highlight 'tma_frontend_bound'. This metric may be drilled into with +'tma_frontend_bound_group' with +'perf stat -M tma_frontend_bound_group...'. -The availability of the top-down metrics level depends on the hardware. For -example, Ice Lake only supports L1 top-down metrics. The Sapphire Rapids -supports both L1 and L2 top-down metrics. - -Default: 0 means the max level that the current hardware support. Error out if the input is higher than the supported max level. --no-merge:: |