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Date:   Tue, 12 Mar 2019 17:29:03 +0000
From:   Song Liu <songliubraving@...com>
To:     Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
CC:     "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kernel Team <Kernel-team@...com>,
        Peter Zijlstra <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        "Jiri Olsa" <jolsa@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
        "sdf@...ichev.me" <sdf@...ichev.me>
Subject: Re: [PATCH v9 perf,bpf 09/15] perf, bpf: save btf information as
 headers to perf.data



> On Mar 12, 2019, at 10:05 AM, Arnaldo Carvalho de Melo <arnaldo.melo@...il.com> wrote:
> 
> Em Tue, Mar 12, 2019 at 04:26:17PM +0000, Song Liu escreveu:
>> 
>> 
>>> On Mar 12, 2019, at 8:16 AM, Arnaldo Carvalho de Melo <arnaldo.melo@...il.com> wrote:
>>> 
>>> Em Tue, Mar 12, 2019 at 12:14:05PM -0300, Arnaldo Carvalho de Melo escreveu:
>>>> Em Mon, Mar 11, 2019 at 10:30:45PM -0700, Song Liu escreveu:
>>>>> +static void print_bpf_btf(struct feat_fd *ff, FILE *fp)
>>>>> +{
>>>>> +	struct perf_env *env = &ff->ph->env;
>>>>> +	struct rb_root *root;
>>>>> +	struct rb_node *next;
>>>>> +
>>>>> +	down_read(&env->bpf_progs.lock);
>>>>> +
>>>>> +	root = &env->bpf_progs.btfs;
>>>>> +	next = rb_first(root);
>>>>> +
>>>>> +	while (next) {
>>>>> +		struct btf_node *node;
>>>>> +
>>>>> +		node = rb_entry(next, struct btf_node, rb_node);
>>>>> +		next = rb_next(&node->rb_node);
>>>>> +		fprintf(fp, "# btf info of id %u\n", node->id);
>>>> 
>>>> So, I couldn't get this to work right now, and I have BPF programs that
>>>> are loaded and that have BTF info:
>>>> 
>>>> [root@...co ~]# bpftool prog | tail -6
>>>> 208: tracepoint  name sys_enter  tag 819967866022f1e1  gpl
>>>> 	loaded_at 2019-03-12T11:16:55-0300  uid 0
>>>> 	xlated 528B  jited 381B  memlock 4096B  map_ids 107,106,105
>>>> 209: tracepoint  name sys_exit  tag c1bd85c092d6e4aa  gpl
>>>> 	loaded_at 2019-03-12T11:16:55-0300  uid 0
>>>> 	xlated 256B  jited 191B  memlock 4096B  map_ids 107,106
>>>> [root@...co ~]#
>>>> 
>>>> 
>>>> [root@...co ~]# bpftool map  | tail -6
>>>> 105: perf_event_array  name __augmented_sys  flags 0x0
>>>> 	key 4B  value 4B  max_entries 8  memlock 4096B
>>>> 106: array  name syscalls  flags 0x0
>>>> 	key 4B  value 1B  max_entries 512  memlock 8192B
>>>> 107: hash  name pids_filtered  flags 0x0
>>>> 	key 4B  value 1B  max_entries 64  memlock 8192B
>>>> [root@...co ~]#
>>>> 
>>>> [root@...co ~]# bpftool map dump id 107
>>>> [{
>>>>       "key": 8104,
>>>>       "value": true
>>>>   },{
>>>>       "key": 18868,
>>>>       "value": true
>>>>   }
>>>> ]
>>>> [root@...co ~]# ps ax|egrep 8104\|18868 | grep -v grep
>>>> 8104 pts/8    S+     0:07 trace -e recvmmsg
>>>> 18868 ?        Ssl   21:21 /usr/libexec/gnome-terminal-server
>>>> [root@...co ~]#
>>>> 
>>>> So I was expecting to see those btf lines there :-\
>>>> 
>>>> All the patches up to this point I have already merged and tested in my
>>>> local branch.
>>>> 
>>>> Will continue right after lunch to try to figure out why this BTF info
>>>> isn't landing on this new header feature...
>>> 
>>> I've pushed what I have to my git.kernel.org repo, branch
>>> tmp.perf/bpf-annotate.
>>> 
>>> git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git tmp.perf/bpf-annotate
>>> 
>>> The HEAD is this cset.
> 
>> I am not sure I fully understand the problem here. 
> 
> Trying to say it another way, when I start 'perf record', with the
> patches in your series up to this one ('[PATCH v9 perf,bpf 09/15] perf,
> bpf: save btf information as headers to perf.data'), and while there is
> a BPF program running, that has BTF attached to it as can be seen by
> using 'bpf map dump', 'perf report --header-only' isn't showing any line
> with 'btf' on it.
> 
> So, using -v I notice that it is failing to get enable attr.bpf_event
> and attr.ksymbol, which makes me go get another coffee to check that the
> kernel was built from my 5.1 tree that has those events and not 5.0 that
> doesn't ;-\ Sorry for the noise, will get back here after I check all
> this :-)
> 
> But to recap, the BPF events I was getting were the synthesized ones...

Yeah, to capture the short living BPF/BTF, we need patch 15/15 of the set. 

Thanks,
Song

> 
> [root@...co ~]# perf record -vv
> Using CPUID GenuineIntel-6-8E-A
> intel_pt default config: tsc,mtc,mtc_period=3,psb_period=3,pt,branch
> nr_cblocks: 0
> affinity: SYS
> ------------------------------------------------------------
> perf_event_attr:
>  size                             112
>  { sample_period, sample_freq }   4000
>  sample_type                      IP|TID|TIME|CPU|PERIOD
>  read_format                      ID
>  disabled                         1
>  inherit                          1
>  mmap                             1
>  comm                             1
>  freq                             1
>  task                             1
>  precise_ip                       3
>  sample_id_all                    1
>  exclude_guest                    1
>  mmap2                            1
>  comm_exec                        1
>  ksymbol                          1
>  bpf_event                        1
> ------------------------------------------------------------
> sys_perf_event_open: pid -1  cpu 0  group_fd -1  flags 0x8
> sys_perf_event_open failed, error -22
> switching off bpf_event
> ------------------------------------------------------------
> perf_event_attr:
>  size                             112
>  { sample_period, sample_freq }   4000
>  sample_type                      IP|TID|TIME|CPU|PERIOD
>  read_format                      ID
>  disabled                         1
>  inherit                          1
>  mmap                             1
>  comm                             1
>  freq                             1
>  task                             1
>  precise_ip                       3
>  sample_id_all                    1
>  exclude_guest                    1
>  mmap2                            1
>  comm_exec                        1
>  ksymbol                          1
> ------------------------------------------------------------
> sys_perf_event_open: pid -1  cpu 0  group_fd -1  flags 0x8
> sys_perf_event_open failed, error -22
> switching off ksymbol
> ------------------------------------------------------------
> perf_event_attr:
>  size                             112
>  { sample_period, sample_freq }   4000
>  sample_type                      IP|TID|TIME|CPU|PERIOD
>  read_format                      ID
>  disabled                         1
>  inherit                          1
>  mmap                             1
>  comm                             1
>  freq                             1
>  task                             1
>  precise_ip                       3
>  sample_id_all                    1
>  exclude_guest                    1
>  mmap2                            1
>  comm_exec                        1
> ------------------------------------------------------------
> sys_perf_event_open: pid -1  cpu 0  group_fd -1  flags 0x8 = 4
> sys_perf_event_open: pid -1  cpu 1  group_fd -1  flags 0x8 = 5
> sys_perf_event_open: pid -1  cpu 2  group_fd -1  flags 0x8 = 6
> sys_perf_event_open: pid -1  cpu 3  group_fd -1  flags 0x8 = 7
> sys_perf_event_open: pid -1  cpu 4  group_fd -1  flags 0x8 = 8
> sys_perf_event_open: pid -1  cpu 5  group_fd -1  flags 0x8 = 9
> sys_perf_event_open: pid -1  cpu 6  group_fd -1  flags 0x8 = 10
> sys_perf_event_open: pid -1  cpu 7  group_fd -1  flags 0x8 = 11
> mmap size 528384B
> perf event ring buffer mmapped per cpu
> Synthesizing TSC conversion information

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