linux-kernel - Re: [RFC/PATCHSET 0/5] perf ftrace: Implement function latency histogram (v1)

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Message-ID: <YboKAvgX7SIiUcoN@kernel.org>
Date:   Wed, 15 Dec 2021 12:30:10 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Jiri Olsa <jolsa@...hat.com>, Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Ian Rogers <irogers@...gle.com>,
        Stephane Eranian <eranian@...gle.com>,
        Song Liu <songliubraving@...com>,
        Changbin Du <changbin.du@...il.com>
Subject: Re: [RFC/PATCHSET 0/5] perf ftrace: Implement function latency
 histogram (v1)

Em Mon, Dec 13, 2021 at 11:40:16AM -0800, Namhyung Kim escreveu:
> On Mon, Dec 13, 2021 at 10:24 AM Arnaldo Carvalho de Melo
> <acme@...nel.org> wrote:
> >
> > Em Mon, Nov 29, 2021 at 03:18:25PM -0800, Namhyung Kim escreveu:
> > > Hello,
> > >
> > > I've implemented 'latency' subcommand in the perf ftrace command to
> > > show a histogram of function latency.
> >
> > This still applies cleanly, I'll test it later.
> 
> Thank you Arnaldo!  While I have some small modifications
> but the functionality should be the same.  Please let me know
> if you have any suggestions.

So, it is failing here with:

⬢[acme@...lbox perf]$ m
make: Entering directory '/var/home/acme/git/perf/tools/perf'
  BUILD:   Doing 'make -j32' parallel build
  CC      /tmp/build/perf/perf-read-vdso32
  LINK    /tmp/build/perf/libperf-jvmti.so
make[3]: Nothing to be done for 'install_headers'.
  CLANG   /tmp/build/perf/util/bpf_skel/.tmp/func_latency.bpf.o
  DESCEND plugins
  PERF_VERSION = 5.16.rc5.g6924c0713d69
  GEN     perf-archive
  GEN     perf-with-kcore
  GEN     perf-iostat
  GEN     /tmp/build/perf/python/perf.so
  INSTALL trace_plugins
  GENSKEL /tmp/build/perf/util/bpf_skel/func_latency.skel.h
  CC      /tmp/build/perf/builtin-ftrace.o
  CC      /tmp/build/perf/util/header.o
  CC      /tmp/build/perf/util/bpf_ftrace.o
util/bpf_ftrace.c: In function ‘perf_ftrace__latency_prepare_bpf’:
util/bpf_ftrace.c:18:13: error: unused variable ‘fd’ [-Werror=unused-variable]
   18 |         int fd, err;
      |             ^~
util/bpf_ftrace.c: In function ‘perf_ftrace__latency_read_bpf’:
util/bpf_ftrace.c:86:21: error: implicit declaration of function ‘cpu__max_cpu’ [-Werror=implicit-function-declaration]
   86 |         int ncpus = cpu__max_cpu();
      |                     ^~~~~~~~~~~~
cc1: all warnings being treated as errors
make[4]: *** [/var/home/acme/git/perf/tools/build/Makefile.build:96: /tmp/build/perf/util/bpf_ftrace.o] Error 1
make[4]: *** Waiting for unfinished jobs....
make[3]: *** [/var/home/acme/git/perf/tools/build/Makefile.build:139: util] Error 2
make[2]: *** [Makefile.perf:665: /tmp/build/perf/perf-in.o] Error 2
make[1]: *** [Makefile.perf:240: sub-make] Error 2
make: *** [Makefile:113: install-bin] Error 2
make: Leaving directory '/var/home/acme/git/perf/tools/perf'

 Performance counter stats for 'make -k BUILD_BPF_SKEL=1 CORESIGHT=1 PYTHON=python3 O=/tmp/build/perf -C tools/perf install-bin':

     8,018,756,380      cycles:u
    14,452,278,281      instructions:u            #    1.80  insn per cycle

       2.250520538 seconds time elapsed

       1.834706000 seconds user
       0.876410000 seconds sys


⬢[acme@...lbox perf]$

⬢[acme@...lbox perf]$ git log --oneline -5
6924c0713d691a6f (HEAD) perf ftrace: Add -b/--use-bpf option for latency subcommand
c96f789bf6313259 perf ftrace: Add 'latency' subcommand
0c5041e1141b53d3 perf ftrace: Move out common code from __cmd_ftrace
8b4a91a9a0b4fbf6 perf ftrace: Add 'trace' subcommand
6bf2efd9d99f3a14 perf arch: Support register names from all archs
⬢[acme@...lbox perf]$

Fixed with:


diff --git a/tools/perf/util/bpf_ftrace.c b/tools/perf/util/bpf_ftrace.c
index 1975a6fe73c9fa8b..f5b49fc056ab8b95 100644
--- a/tools/perf/util/bpf_ftrace.c
+++ b/tools/perf/util/bpf_ftrace.c
@@ -5,6 +5,7 @@
 
 #include <linux/err.h>
 
+#include "util/cpumap.h"
 #include "util/ftrace.h"
 #include "util/debug.h"
 #include "util/bpf_counter.h"
@@ -15,7 +16,7 @@ static struct func_latency_bpf *skel;
 
 int perf_ftrace__latency_prepare_bpf(struct perf_ftrace *ftrace)
 {
-	int fd, err;
+	int err;
 	struct filter_entry *func;
 	struct bpf_link *begin_link, *end_link;