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Date:   Mon, 9 Mar 2020 18:24:22 +0000
From:   Song Liu <songliubraving@...com>
To:     Quentin Monnet <quentin@...valent.com>
CC:     Jiri Olsa <jolsa@...hat.com>, Networking <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>, 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 9, 2020, at 11:04 AM, Quentin Monnet <quentin@...valent.com> wrote:
> 
> 2020-03-04 21:39 UTC+0000 ~ Song Liu <songliubraving@...com>
>> 
>> 
>>> 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
>> 
> 
> Thinking about this requirement again... Do you think it would be worth
> adding (as a follow-up) a feature check on the availability of clang
> with global data support to bpftool's Makefile? So that we could compile
> out program profiling if clang is not present or does not support it.
> Just like libbfd support is optional already.
> 
> I'm asking mostly because a number of distributions now package bpftool,
> and e.g. Ubuntu builds it from kernel source when creating its
> linux-images and linux-tools-* packages. And I am pretty sure the build
> environment does not have latest clang/LLVM, but it would be great to
> remain able to build bpftool.

Yeah, I think it is a good idea. Some more Makefile fun. ;)

Thanks,
Song

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