Commit-ID: 4e303fbe2d95806c875f5ebfcb3d980e20b4bd83
Gitweb: https://git.kernel.org/tip/4e303fbe2d95806c875f5ebfcb3d980e20b4bd83
Author: Arnaldo Carvalho de Melo <[email protected]>
AuthorDate: Fri, 26 Oct 2018 15:55:23 -0300
Committer: Arnaldo Carvalho de Melo <[email protected]>
CommitDate: Tue, 30 Oct 2018 11:46:23 -0300
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 <[email protected]>
Acked-by: Kan Liang <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Jin Yao <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Wang Nan <[email protected]>
Fixes: ebebbf082357 ("perf top: Switch default mode to overwrite mode")
Link: https://lkml.kernel.org/n/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>
---
tools/perf/Documentation/perf-top.txt | 5 +++++
tools/perf/builtin-top.c | 2 ++
2 files changed, 7 insertions(+)
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"),
