Messages in this thread Patch in this message |  | | From | Song Liu <> | Subject | Re: [PATCH v6 3/4] perf-stat: enable counting events for BPF programs | Date | Tue, 29 Dec 2020 05:53:47 +0000 |
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> On Dec 28, 2020, at 3:43 PM, Song Liu <songliubraving@fb.com> wrote: > > > >> On Dec 28, 2020, at 12:11 PM, Arnaldo Carvalho de Melo <acme@kernel.org> 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 tried it on CentOS Stream release 8, with
gcc version 8.4.1 20200928 (Red Hat 8.4.1-1) (GCC) clang version 11.0.0 (Red Hat 11.0.0-0.2.rc2.module_el8.4.0+533+50191577)
Unfortunately, I still cannot repro it.
I didn't find the issue while looking through the code. AFAICS, the code fail over when the skeleton is not ready, so bpf_program_profiler__read() should find a valid skeleton.
Could you please help run the test with the following patch? The patch is also available at
https://git.kernel.org/pub/scm/linux/kernel/git/song/linux.git perf-dash-b
Thanks, Song
diff --git i/tools/perf/util/bpf_counter.c w/tools/perf/util/bpf_counter.c index f2cb86a40c882..e09c571365b56 100644 --- i/tools/perf/util/bpf_counter.c +++ w/tools/perf/util/bpf_counter.c @@ -46,8 +46,10 @@ static int bpf_program_profiler__destroy(struct evsel *evsel) { struct bpf_counter *counter;
- list_for_each_entry(counter, &evsel->bpf_counter_list, list) + list_for_each_entry(counter, &evsel->bpf_counter_list, list) { + pr_debug("%s counter = %lx\n", __func__, (unsigned long)counter); bpf_prog_profiler_bpf__destroy(counter->skel); + } INIT_LIST_HEAD(&evsel->bpf_counter_list); return 0; } @@ -141,8 +143,14 @@ static int bpf_program_profiler_load_one(struct evsel *evsel, u32 prog_id) counter->skel = skel; list_add(&counter->list, &evsel->bpf_counter_list); close(prog_fd); + pr_debug("%s counter = %lx\n", __func__, (unsigned long)counter); + pr_debug("%s skel = %lx\n", __func__, (unsigned long)skel); + pr_debug("%s return 0\n", __func__); return 0; err_out: + pr_debug("%s counter = %lx\n", __func__, (unsigned long)counter); + pr_debug("%s skel = %lx\n", __func__, (unsigned long)skel); + pr_debug("%s return -1\n", __func__); free(counter); close(prog_fd); return -1; @@ -214,11 +222,22 @@ static int bpf_program_profiler__read(struct evsel *evsel) list_for_each_entry(counter, &evsel->bpf_counter_list, list) { struct bpf_prog_profiler_bpf *skel = counter->skel;
+ pr_debug("%s counter = %lx\n", __func__, (unsigned long)counter); + pr_debug("%s skel = %lx\n", __func__, (unsigned long)skel); + if (!skel) { + pr_err("%s !skel\n", __func__); + continue; + } + if (!skel->maps.accum_readings) { + pr_err("%s !skel->maps.accum_readings", __func__); + continue; + } + reading_map_fd = bpf_map__fd(skel->maps.accum_readings);
err = bpf_map_lookup_elem(reading_map_fd, &key, values); if (err) { - fprintf(stderr, "failed to read value\n"); + pr_err("failed to read value\n"); return err; }
@@ -240,6 +259,8 @@ static int bpf_program_profiler__install_pe(struct evsel *evsel, int cpu,
list_for_each_entry(counter, &evsel->bpf_counter_list, list) { skel = counter->skel; + pr_debug("%s counter = %lx\n", __func__, (unsigned long)counter); + pr_debug("%s skel = %lx\n", __func__, (unsigned long)skel); ret = bpf_map_update_elem(bpf_map__fd(skel->maps.events), &cpu, &fd, BPF_ANY); if (ret)
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