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authorTony Jones <tonyj@suse.de>2020-03-25 09:40:53 -0700
committerArnaldo Carvalho de Melo <acme@redhat.com>2020-03-25 16:13:21 -0300
commiteadcaa3dfd706bbf46682c8b8b5979262443c3c3 (patch)
treea2e0f4f6d2f875492d1a458bfa6413397814e350 /tools/perf/Documentation/perf-record.txt
parent0d33b34352531ff7029c58eda2321340c0ea3f5f (diff)
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perf callchain: Update docs regarding kernel/user space unwinding
The method of unwinding for kernel space is defined by the kernel config, not by the value of --call-graph. Improve the documentation to reflect this. Signed-off-by: Tony Jones <tonyj@suse.de> Link: http://lore.kernel.org/lkml/20200325164053.10177-1-tonyj@suse.de Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Diffstat (limited to 'tools/perf/Documentation/perf-record.txt')
-rw-r--r--tools/perf/Documentation/perf-record.txt18
1 files changed, 12 insertions, 6 deletions
diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index 7f4db7592467..b25e028458e2 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -237,16 +237,22 @@ OPTIONS
option and remains only for backward compatibility. See --event.
-g::
- Enables call-graph (stack chain/backtrace) recording.
+ Enables call-graph (stack chain/backtrace) recording for both
+ kernel space and user space.
--call-graph::
Setup and enable call-graph (stack chain/backtrace) recording,
- implies -g. Default is "fp".
+ implies -g. Default is "fp" (for user space).
- Allows specifying "fp" (frame pointer) or "dwarf"
- (DWARF's CFI - Call Frame Information) or "lbr"
- (Hardware Last Branch Record facility) as the method to collect
- the information used to show the call graphs.
+ The unwinding method used for kernel space is dependent on the
+ unwinder used by the active kernel configuration, i.e
+ CONFIG_UNWINDER_FRAME_POINTER (fp) or CONFIG_UNWINDER_ORC (orc)
+
+ Any option specified here controls the method used for user space.
+
+ Valid options are "fp" (frame pointer), "dwarf" (DWARF's CFI -
+ Call Frame Information) or "lbr" (Hardware Last Branch Record
+ facility).
In some systems, where binaries are build with gcc
--fomit-frame-pointer, using the "fp" method will produce bogus