netdev - Re: [PATCH v4 bpf-next 0/4] bpftool: introduce prog profile

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Message-ID: <4C0824FE-37CB-4660-BAE0-0EAE8F6BF8A0@fb.com>
Date:   Wed, 4 Mar 2020 21:39:52 +0000
From:   Song Liu <songliubraving@...com>
To:     Jiri Olsa <jolsa@...hat.com>
CC:     Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        "quentin@...valent.com" <quentin@...valent.com>,
        Kernel Team <Kernel-team@...com>,
        "ast@...nel.org" <ast@...nel.org>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        "arnaldo.melo@...il.com" <arnaldo.melo@...il.com>,
        "jolsa@...nel.org" <jolsa@...nel.org>
Subject: Re: [PATCH v4 bpf-next 0/4] bpftool: introduce prog profile



> On Mar 4, 2020, at 1:29 PM, Jiri Olsa <jolsa@...hat.com> wrote:
> 
> On Wed, Mar 04, 2020 at 09:16:29PM +0000, Song Liu wrote:
>> 
>> 
>>> On Mar 4, 2020, at 12:41 PM, Jiri Olsa <jolsa@...hat.com> wrote:
>>> 
>>> On Wed, Mar 04, 2020 at 08:08:07PM +0100, Jiri Olsa wrote:
>>>> On Wed, Mar 04, 2020 at 10:07:06AM -0800, Song Liu wrote:
>>>>> This set introduces bpftool prog profile command, which uses hardware
>>>>> counters to profile BPF programs.
>>>>> 
>>>>> This command attaches fentry/fexit programs to a target program. These two
>>>>> programs read hardware counters before and after the target program and
>>>>> calculate the difference.
>>>>> 
>>>>> Changes v3 => v4:
>>>>> 1. Simplify err handling in profile_open_perf_events() (Quentin);
>>>>> 2. Remove redundant p_err() (Quentin);
>>>>> 3. Replace tab with space in bash-completion; (Quentin);
>>>>> 4. Fix typo _bpftool_get_map_names => _bpftool_get_prog_names (Quentin).
>>>> 
>>>> hum, I'm getting:
>>>> 
>>>> 	[jolsa@...l-r440-01 bpftool]$ pwd
>>>> 	/home/jolsa/linux-perf/tools/bpf/bpftool
>>>> 	[jolsa@...l-r440-01 bpftool]$ make
>>>> 	...
>>>> 	make[1]: Leaving directory '/home/jolsa/linux-perf/tools/lib/bpf'
>>>> 	  LINK     _bpftool
>>>> 	make: *** No rule to make target 'skeleton/profiler.bpf.c', needed by 'skeleton/profiler.bpf.o'.  Stop.
>>> 
>>> ok, I had to apply your patches by hand, because 'git am' refused to
>>> due to fuzz.. so some of you new files did not make it to my tree ;-)
>>> 
>>> anyway I hit another error now:
>>> 
>>> 	  CC       prog.o
>>> 	In file included from prog.c:1553:
>>> 	profiler.skel.h: In function ‘profiler_bpf__create_skeleton’:
>>> 	profiler.skel.h:136:35: error: ‘struct profiler_bpf’ has no member named ‘rodata’
>>> 	  136 |  s->maps[4].mmaped = (void **)&obj->rodata;
>>> 	      |                                   ^~
>>> 	prog.c: In function ‘profile_read_values’:
>>> 	prog.c:1650:29: error: ‘struct profiler_bpf’ has no member named ‘rodata’
>>> 	 1650 |  __u32 m, cpu, num_cpu = obj->rodata->num_cpu;
>>> 
>>> I'll try to figure it out.. might be error on my end
>>> 
>>> do you have git repo with these changes?
>> 
>> I pushed it to 
>> 
>> https://git.kernel.org/pub/scm/linux/kernel/git/song/linux.git/tree/?h=bpf-per-prog-stats
> 
> still the same:
> 
> 	[jolsa@...l-r440-01 bpftool]$ git show --oneline HEAD | head -1
> 	7bbda5cca00a bpftool: fix typo in bash-completion
> 	[jolsa@...l-r440-01 bpftool]$ make 
> 	make[1]: Entering directory '/home/jolsa/linux-perf/tools/lib/bpf'
> 	make[1]: Leaving directory '/home/jolsa/linux-perf/tools/lib/bpf'
> 	  CC       prog.o
> 	In file included from prog.c:1553:
> 	profiler.skel.h: In function ‘profiler_bpf__create_skeleton’:
> 	profiler.skel.h:136:35: error: ‘struct profiler_bpf’ has no member named ‘rodata’
> 	  136 |  s->maps[4].mmaped = (void **)&obj->rodata;
> 	      |                                   ^~
> 	prog.c: In function ‘profile_read_values’:
> 	prog.c:1650:29: error: ‘struct profiler_bpf’ has no member named ‘rodata’
> 	 1650 |  __u32 m, cpu, num_cpu = obj->rodata->num_cpu;
> 	      |                             ^~
> 	prog.c: In function ‘profile_open_perf_events’:
> 	prog.c:1810:19: error: ‘struct profiler_bpf’ has no member named ‘rodata’
> 	 1810 |   sizeof(int), obj->rodata->num_cpu * obj->rodata->num_metric);
> 	      |                   ^~
> 	prog.c:1810:42: error: ‘struct profiler_bpf’ has no member named ‘rodata’
> 	 1810 |   sizeof(int), obj->rodata->num_cpu * obj->rodata->num_metric);
> 	      |                                          ^~
> 	prog.c:1825:26: error: ‘struct profiler_bpf’ has no member named ‘rodata’
> 	 1825 |   for (cpu = 0; cpu < obj->rodata->num_cpu; cpu++) {
> 	      |                          ^~
> 	prog.c: In function ‘do_profile’:
> 	prog.c:1904:13: error: ‘struct profiler_bpf’ has no member named ‘rodata’
> 	 1904 |  profile_obj->rodata->num_cpu = num_cpu;
> 	      |             ^~
> 	prog.c:1905:13: error: ‘struct profiler_bpf’ has no member named ‘rodata’
> 	 1905 |  profile_obj->rodata->num_metric = num_metric;
> 	      |             ^~
> 	make: *** [Makefile:129: prog.o] Error 1

I guess you need a newer version of clang that supports global data in BPF programs. 

Thanks,
Song