Em Mon, Dec 28, 2020 at 11:43:25PM +0000, Song Liu escreveu:
>
>
> > On Dec 28, 2020, at 12:11 PM, Arnaldo Carvalho de Melo <[email protected]>
> > wrote:
> >
> > Em Mon, Dec 28, 2020 at 09:40:53AM -0800, Song Liu escreveu:
> >> Introduce perf-stat -b option, which counts events for BPF programs, like:
> >>
> >> [root@localhost ~]# ~/perf stat -e ref-cycles,cycles -b 254 -I 1000
> >> 1.487903822 115,200 ref-cycles
> >> 1.487903822 86,012 cycles
> >> 2.489147029 80,560 ref-cycles
> >> 2.489147029 73,784 cycles
> >> 3.490341825 60,720 ref-cycles
> >> 3.490341825 37,797 cycles
> >> 4.491540887 37,120 ref-cycles
> >> 4.491540887 31,963 cycles
> >>
> >> The example above counts cycles and ref-cycles of BPF program of id 254.
> >> This is similar to bpftool-prog-profile command, but more flexible.
> >>
> >> perf-stat -b creates per-cpu perf_event and loads fentry/fexit BPF
> >> programs (monitor-progs) to the target BPF program (target-prog). The
> >> monitor-progs read perf_event before and after the target-prog, and
> >> aggregate the difference in a BPF map. Then the user space reads data
> >> from these maps.
> >>
> >> A new struct bpf_counter is introduced to provide common interface that
> >> uses BPF programs/maps to count perf events.
> >
> > Segfaulting here:
> >
> > [root@five ~]# bpftool prog | grep tracepoint
> > 110: tracepoint name syscall_unaugme tag 57cd311f2e27366b gpl
> > 111: tracepoint name sys_enter_conne tag 3555418ac9476139 gpl
> > 112: tracepoint name sys_enter_sendt tag bc7fcadbaf7b8145 gpl
> > 113: tracepoint name sys_enter_open tag 0e59c3ac2bea5280 gpl
> > 114: tracepoint name sys_enter_opena tag 0baf443610f59837 gpl
> > 115: tracepoint name sys_enter_renam tag 24664e4aca62d7fa gpl
> > 116: tracepoint name sys_enter_renam tag 20093e51a8634ebb gpl
> > 117: tracepoint name sys_enter tag 0bc3fc9d11754ba1 gpl
> > 118: tracepoint name sys_exit tag 29c7ae234d79bd5c gpl
> > [root@five ~]#
> > [root@five ~]# gdb perf
> > GNU gdb (GDB) Fedora 10.1-2.fc33
> > Reading symbols from perf...
> > (gdb) run stat -e instructions,cycles -b 113 -I 1000
> > Starting program: /root/bin/perf stat -e instructions,cycles -b 113 -I 1000
> > [Thread debugging using libthread_db enabled]
> > Using host libthread_db library "/lib64/libthread_db.so.1".
> > libbpf: elf: skipping unrecognized data section(9) .eh_frame
> > libbpf: elf: skipping relo section(15) .rel.eh_frame for section(9)
> > .eh_frame
> > libbpf: elf: skipping unrecognized data section(9) .eh_frame
> > libbpf: elf: skipping relo section(15) .rel.eh_frame for section(9)
> > .eh_frame
> >
> > Program received signal SIGSEGV, Segmentation fault.
> > 0x000000000058d55b in bpf_program_profiler__read (evsel=0xc612c0) at
> > util/bpf_counter.c:217
> > 217 reading_map_fd = bpf_map__fd(skel->maps.accum_readings);
> > (gdb) bt
> > #0 0x000000000058d55b in bpf_program_profiler__read (evsel=0xc612c0) at
> > util/bpf_counter.c:217
> > #1 0x0000000000000000 in ?? ()
> > (gdb)
> >
> > [acme@five perf]$ clang -v |& head -2
> > clang version 11.0.0 (Fedora 11.0.0-2.fc33)
> > Target: x86_64-unknown-linux-gnu
> > [acme@five perf]$
> >
> > Do you need any extra info?
>
> Hmm... I am not able to reproduce this. I am trying to setup an environment
> similar
> to fc33 (clang 11, etc.). Does this segfault every time, and on all programs?
I'll try it with a BPF proggie attached to a kprobes, but here is
something else I noticed:
[root@five perf]# export PYTHONPATH=/tmp/build/perf/python
[root@five perf]# tools/perf/python/twatch.py
Traceback (most recent call last):
File "/home/acme/git/perf/tools/perf/python/twatch.py", line 9, in <module>
import perf
ImportError: /tmp/build/perf/python/perf.cpython-39-x86_64-linux-gnu.so:
undefined symbol: bpf_counter__destroy
[root@five perf]# perf test python
19: 'import perf' in python : FAILED!
[root@five perf]# perf test -v python
19: 'import perf' in python :
--- start ---
test child forked, pid 3198864
python usage test: "echo "import sys ;
sys.path.append('/tmp/build/perf/python'); import perf" | '/usr/bin/python3' "
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ImportError: /tmp/build/perf/python/perf.cpython-39-x86_64-linux-gnu.so:
undefined symbol: bpf_counter__destroy
test child finished with -1
---- end ----
'import perf' in python: FAILED!
[root@five perf]#
This should be trivial, I hope, just add the new object file to
tools/perf/util/python-ext-sources, then do a 'perf test python', if it
fails, use 'perf test -v python' to see what is preventing the python
binding from loading.
- Arnaldo
