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authorArnaldo Carvalho de Melo <acme@redhat.com>2018-10-26 15:55:23 -0300
committerArnaldo Carvalho de Melo <acme@redhat.com>2018-10-30 11:46:23 -0300
commit4e303fbe2d95806c875f5ebfcb3d980e20b4bd83 (patch)
tree2ed3908482f947d3ef5abd27f0bdd6f35dfe9081 /tools
parent23c07a23cbed389d0b9c7a06486574621df8d1a4 (diff)
perf top: Allow disabling the overwrite mode
In ebebbf082357 ("perf top: Switch default mode to overwrite mode") we forgot to leave a way to disable that new default, add a --overwrite option that can be disabled using --no-overwrite, since the code already in such a way that we can readily disable this mode. This is useful when investigating bugs with this mode like the recent report from David Miller where lots of unknown symbols appear due to disabling the events while processing them which disables all record types, not just PERF_RECORD_SAMPLE, which makes it impossible to resolve maps when we lose PERF_RECORD_MMAP records. This can be easily seen while building a kernel, when there are lots of short lived processes. Reported-by: David Miller <davem@davemloft.net> Acked-by: Kan Liang <kan.liang@intel.com> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: David Ahern <dsahern@gmail.com> Cc: Jin Yao <yao.jin@linux.intel.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Wang Nan <wangnan0@huawei.com> Fixes: ebebbf082357 ("perf top: Switch default mode to overwrite mode") Link: https://lkml.kernel.org/n/tip-oqgsz2bq4kgrnnajrafcdhie@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Diffstat (limited to 'tools')
-rw-r--r--tools/perf/Documentation/perf-top.txt5
-rw-r--r--tools/perf/builtin-top.c2
2 files changed, 7 insertions, 0 deletions
diff --git a/tools/perf/Documentation/perf-top.txt b/tools/perf/Documentation/perf-top.txt
index 114fda12aa49..d4be6061fe1c 100644
--- a/tools/perf/Documentation/perf-top.txt
+++ b/tools/perf/Documentation/perf-top.txt
@@ -242,6 +242,11 @@ Default is to monitor all CPUS.
--hierarchy::
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.
+
--force::
Don't do ownership validation.
diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index d21d8751e749..214fad747b04 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -1372,6 +1372,8 @@ int cmd_top(int argc, const char **argv)
"Show raw trace event output (do not use print fmt or plugins)"),
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"),
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"),