[PATCH v2] perf record: Add doc for bpf event selection

Changbin Du
2019-02-01T13:47:20Z

Add document for how to pass bpf program with perf.

Cc: Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
Signed-off-by: Changbin Du <changbin.du@gmail.com>

---
v2: fix grammar and add llvm section in perf-config.txt.
---
tools/perf/Documentation/perf-config.txt | 31 ++++++++++++++++++++++++
tools/perf/Documentation/perf-record.txt | 14 +++++++++++
2 files changed, 45 insertions(+)

diff --git a/tools/perf/Documentation/perf-config.txt b/tools/perf/Documentation/perf-config.txt
index 4ac7775fbc11..86f3dcc15f83 100644
--- a/tools/perf/Documentation/perf-config.txt
+++ b/tools/perf/Documentation/perf-config.txt
@@ -120,6 +120,10 @@ Given a $HOME/.perfconfig like this:
children = true
group = true

+ [llvm]
+ dump-obj = true
+ clang-opt = -g
+
You can hide source code of annotate feature setting the config to false with

% perf config annotate.hide_src_code=true
@@ -553,6 +557,33 @@ trace.*::
trace.show_zeros::
Do not suppress syscall arguments that are equal to zero.

+llvm.*::
+ llvm.clang-path::
+ Path to clang. If omit, search it from $PATH.
+
+ llvm.clang-bpf-cmd-template::
+ Cmdline template. Below lines show its default value. Environment
+ variable is used to pass options.
+ "$CLANG_EXEC -D__KERNEL__ $CLANG_OPTIONS $KERNEL_INC_OPTIONS \
+ -Wno-unused-value -Wno-pointer-sign -working-directory \
+ $WORKING_DIR -c $CLANG_SOURCE -target bpf -O2 -o -"
+
+ llvm.clang-opt::
+ Options passed to clang.
+
+ llvm.kbuild-dir::
+ kbuild directory. If not set, use /lib/modules/`uname -r`/build.
+ If set to "" deliberately, skip kernel header auto-detector.
+
+ llvm.kbuild-opts::
+ Options passed to 'make' when detecting kernel header options.
+
+ llvm.dump-obj::
+ Enable perf dump BPF object files compiled by LLVM.
+
+ llvm.opts::
+ Options passed to llc.
+
SEE ALSO
--------
linkperf:perf[1]
diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index d232b13ea713..aa94ec7335df 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -88,6 +88,20 @@ OPTIONS
If you want to profile write accesses in [0x1000~1008), just set
'mem:0x1000/8:w'.

+ - a bpf source file (ending in .c) or a precompiled object file (ending
+ in .o) selects one or more BPF events.
+ The BPF program can attach to various perf events based on section
+ names.
+
+ When passing '.c', perf searches an installed LLVM to compile it into
+ an object file first. Optional clang options can be pased by option
+ '--clang-opt'.
+
+ perf record --clang-opt "-DLINUX_VERSION_CODE=0x50000" \
+ -e ./tests/bpf-script-example.c
+
+ Note: '--clang-opt' must place before '--event'.
+
- a group of events surrounded by a pair of brace ("{event1,event2,...}").
Each event is separated by commas and the group should be quoted to
prevent the shell interpretation. You also need to use --group on
--
2.19.1