diff options
| -rw-r--r-- | tools/perf/Documentation/perf-top.txt | 11 | ||||
| -rw-r--r-- | tools/perf/builtin-top.c | 11 |
2 files changed, 17 insertions, 5 deletions
diff --git a/tools/perf/Documentation/perf-top.txt b/tools/perf/Documentation/perf-top.txt index d4be6061fe1c..808b664343c9 100644 --- a/tools/perf/Documentation/perf-top.txt +++ b/tools/perf/Documentation/perf-top.txt @@ -243,9 +243,14 @@ Default is to monitor all CPUS. Enable hierarchy output. --overwrite:: - This is the default, but for investigating problems with it or any other strange - behaviour like lots of unknown samples, we may want to disable this mode by using - --no-overwrite. + Enable this to use just the most recent records, which helps in high core count + machines such as Knights Landing/Mill, but right now is disabled by default as + the pausing used in this technique is leading to loss of metadata events such + as PERF_RECORD_MMAP which makes 'perf top' unable to resolve samples, leading + to lots of unknown samples appearing on the UI. Enable this if you are in such + machines and profiling a workload that doesn't creates short lived threads and/or + doesn't uses many executable mmap operations. Work is being planed to solve + this situation, till then, this will remain disabled by default. --force:: Don't do ownership validation. diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c index 214fad747b04..8e29e0cc8626 100644 --- a/tools/perf/builtin-top.c +++ b/tools/perf/builtin-top.c @@ -1257,7 +1257,14 @@ int cmd_top(int argc, const char **argv) .uses_mmap = true, }, .proc_map_timeout = 500, - .overwrite = 1, + /* + * FIXME: This will lose PERF_RECORD_MMAP and other metadata + * when we pause, fix that and reenable. Probably using a + * separate evlist with a dummy event, i.e. a non-overwrite + * ring buffer just for metadata events, while PERF_RECORD_SAMPLE + * stays in overwrite mode. -acme + * */ + .overwrite = 0, }, .max_stack = sysctl__max_stack(), .annotation_opts = annotation__default_options, @@ -1373,7 +1380,7 @@ int cmd_top(int argc, const char **argv) OPT_BOOLEAN(0, "hierarchy", &symbol_conf.report_hierarchy, "Show entries in a hierarchy"), OPT_BOOLEAN(0, "overwrite", &top.record_opts.overwrite, - "Use a backward ring buffer, default: yes"), + "Use a backward ring buffer, default: no"), OPT_BOOLEAN(0, "force", &symbol_conf.force, "don't complain, do it"), OPT_UINTEGER(0, "num-thread-synthesize", &top.nr_threads_synthesize, "number of thread to run event synthesize"), |