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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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