Messages in this thread | | | From | Namhyung Kim <> | Subject | [RFC/PATCHSET 0/5] perf ftrace: Implement function latency histogram (v1) | Date | Mon, 29 Nov 2021 15:18:25 -0800 |
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Hello,
I've implemented 'latency' subcommand in the perf ftrace command to show a histogram of function latency.
To handle new subcommands, the existing functionality is moved to 'trace' subcommand while preserving backward compatibility of not having a subcommand at all (defaults to 'trace').
The latency subcommand accepts a target (kernel, for now) function with -T option and shows a histogram like below:
$ sudo ./perf ftrace latency -a -T mutex_lock sleep 1 # DURATION | COUNT | GRAPH | 0 - 1 us | 2686 | ###################### | 1 - 2 us | 976 | ######## | 2 - 4 us | 879 | ####### | 4 - 8 us | 481 | #### | 8 - 16 us | 445 | ### | 16 - 32 us | 1 | | 32 - 64 us | 0 | | 64 - 128 us | 0 | | 128 - 256 us | 0 | | 256 - 512 us | 0 | | 512 - 1024 us | 0 | | 1 - 2 ms | 0 | | 2 - 4 ms | 0 | | 4 - 8 ms | 0 | | 8 - 16 ms | 0 | | 16 - 32 ms | 0 | | 32 - 64 ms | 0 | | 64 - 128 ms | 0 | | 128 - 256 ms | 0 | | 256 - 512 ms | 0 | | 512 - 1024 ms | 0 | | 1 - ... s | 0 | | It basically use the function graph tracer to extract the duration of the function. But with -b/--use-bpf option, it can use BPF to save the histogram in the kernel. For the same function, it gets:
$ sudo ./perf ftrace latency -a -b -T mutex_lock sleep 1 # DURATION | COUNT | GRAPH | 0 - 1 us | 4682 | ############################################# | 1 - 2 us | 11 | | 2 - 4 us | 0 | | 4 - 8 us | 0 | | 8 - 16 us | 7 | | 16 - 32 us | 6 | | 32 - 64 us | 0 | | 64 - 128 us | 0 | | 128 - 256 us | 0 | | 256 - 512 us | 0 | | 512 - 1024 us | 0 | | 1 - 2 ms | 0 | | 2 - 4 ms | 0 | | 4 - 8 ms | 0 | | 8 - 16 ms | 0 | | 16 - 32 ms | 0 | | 32 - 64 ms | 0 | | 64 - 128 ms | 0 | | 128 - 256 ms | 0 | | 256 - 512 ms | 0 | | 512 - 1024 ms | 0 | | 1 - ... s | 0 | |
You can get the patches at 'perf/ftrace-latency-v1' branch on
https://git.kernel.org/pub/scm/linux/kernel/git/namhyung/linux-perf.git
Thanks, Namhyung
Namhyung Kim (5): perf ftrace: Add 'trace' subcommand perf ftrace: Move out common code from __cmd_ftrace perf ftrace: Add 'latency' subcommand perf ftrace: Add -b/--use-bpf option for latency subcommand perf ftrace: Implement cpu and task filters in BPF
tools/perf/Makefile.perf | 2 +- tools/perf/builtin-ftrace.c | 443 +++++++++++++++++--- tools/perf/util/Build | 1 + tools/perf/util/bpf_ftrace.c | 154 +++++++ tools/perf/util/bpf_skel/func_latency.bpf.c | 113 +++++ tools/perf/util/ftrace.h | 81 ++++ 6 files changed, 724 insertions(+), 70 deletions(-) create mode 100644 tools/perf/util/bpf_ftrace.c create mode 100644 tools/perf/util/bpf_skel/func_latency.bpf.c create mode 100644 tools/perf/util/ftrace.h
base-commit: 8ab774587903771821b59471cc723bba6d893942 -- 2.34.0.rc2.393.gf8c9666880-goog
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