Messages in this thread | ![/](/images/icornerl.gif) | | From | Ian Rogers <> | Date | Wed, 6 Apr 2022 09:46:34 -0700 | Subject | Re: [PATCH v13 01/16] perf record: Introduce thread affinity and mmap masks |
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On Tue, Apr 5, 2022 at 9:21 AM Bayduraev, Alexey V <alexey.v.bayduraev@linux.intel.com> wrote: > > On 05.04.2022 1:25, Ian Rogers wrote: > > On Mon, Jan 17, 2022 at 10:38 AM Alexey Bayduraev > > <alexey.v.bayduraev@linux.intel.com> wrote: > >> > >> Introduce affinity and mmap thread masks. Thread affinity mask > > <SNIP> > > > > > In per-thread mode it is possible that cpus is the dummy CPU map here. > > This means that the cpu below has the value -1 and setting bit -1 > > actually has the effect of setting bit 63. Here is a reproduction > > based on the acme/perf/core branch: > > > > ``` > > $ make STATIC=1 DEBUG=1 EXTRA_CFLAGS='-fno-omit-frame-pointer > > -fsanitize=undefined -fno-sanitize-recover' > > $ perf record -o /tmp/perf.data --per-thread true > > tools/include/asm-generic/bitops/atomic.h:10:36: runtime error: shift > > exponent -1 is negative > > $ UBSAN_OPTIONS=abort_on_error=1 gdb --args perf record -o > > /tmp/perf.data --per-thread true > > (gdb) r > > tools/include/asm-generic/bitops/atomic.h:10:36: runtime error: shift > > exponent -1 is negative > > (gdb) bt > > #0 __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:49 > > #1 0x00007ffff71d2546 in __GI_abort () at abort.c:79 > > #2 0x00007ffff640db9f in __sanitizer::Abort () at > > ../../../../src/libsanitizer/sanitizer_common/sanitizer_posix_libcdep.cpp:151 > > #3 0x00007ffff6418efc in __sanitizer::Die () at > > ../../../../src/libsanitizer/sanitizer_common/sanitizer_termination.cpp:58 > > #4 0x00007ffff63fd99e in > > __ubsan::__ubsan_handle_shift_out_of_bounds_abort (Data=<optimized > > out>, LHS=<optimized out>, > > RHS=<optimized out>) at > > ../../../../src/libsanitizer/ubsan/ubsan_handlers.cpp:378 > > #5 0x0000555555c54405 in set_bit (nr=-1, addr=0x555556ecd0a0) > > at tools/include/asm-generic/bitops/atomic.h:10 > > #6 0x0000555555c6ddaf in record__mmap_cpu_mask_init > > (mask=0x555556ecd070, cpus=0x555556ecd050) at builtin-record.c:3333 > > #7 0x0000555555c7044c in record__init_thread_default_masks > > (rec=0x55555681b100 <record>, cpus=0x555556ecd050) at > > builtin-record.c:3668 > > #8 0x0000555555c705b3 in record__init_thread_masks > > (rec=0x55555681b100 <record>) at builtin-record.c:3681 > > #9 0x0000555555c7297a in cmd_record (argc=1, argv=0x7fffffffdcc0) at > > builtin-record.c:3976 > > #10 0x0000555555e06d41 in run_builtin (p=0x555556827538 > > <commands+216>, argc=5, argv=0x7fffffffdcc0) at perf.c:313 > > #11 0x0000555555e07253 in handle_internal_command (argc=5, > > argv=0x7fffffffdcc0) at perf.c:365 > > #12 0x0000555555e07508 in run_argv (argcp=0x7fffffffdb0c, > > argv=0x7fffffffdb00) at perf.c:409 > > #13 0x0000555555e07b32 in main (argc=5, argv=0x7fffffffdcc0) at perf.c:539 > > ``` > > > > Not setting the mask->bits if the cpu map is dummy causes no data to > > be written. Setting mask->bits 0 causes a segv. Setting bit 63 works > > but feels like there are more invariants broken in the code. > > > > Here is a not good workaround patch: > > > > diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c > > index ba74fab02e62..62727b676f98 100644 > > --- a/tools/perf/builtin-record.c > > +++ b/tools/perf/builtin-record.c > > @@ -3329,6 +3329,11 @@ static void record__mmap_cpu_mask_init(struct > > mmap_cpu_mask *mask, struct perf_c > > { > > int c; > > > > + if (cpu_map__is_dummy(cpus)) { > > + set_bit(63, mask->bits); > > + return; > > + } > > + > > for (c = 0; c < cpus->nr; c++) > > set_bit(cpus->map[c].cpu, mask->bits); > > } > > > > Alexey, what should the expected behavior be with per-thread mmaps? > > > > Thanks, > > Ian > > Thanks a lot, > > In case of per-thread mmaps we should initialize thread_data[0]->maps[i] by > evlist->mmap[i]. Looks like this was missed by this patchset. > > Your patch works, because it triggers test_bit() in record__thread_data_init_maps() > and thread_data maps get correctly initialized. > > However, it's better to ignore thread_data->masks in record__mmap_cpu_mask_init() > and setup thread_data maps explicitly for per-thread case. > > Also, to prevent more runtime crashes, --per-thread and --threads > options should be mutually exclusive. > > I will prepare a fix for this issue soon.
Hi Alexey,
sorry to nag, I'm being nagged, is there an ETA on the fix? Is it pragmatic to roll back for now?
Thanks, Ian
> Regards, > Alexey > > > > >> +static void record__free_thread_masks(struct record *rec, int nr_threads) > >> +{ > >> + int t; > >> + > >> + if (rec->thread_masks) > >> + for (t = 0; t < nr_threads; t++) > >> + record__thread_mask_free(&rec->thread_masks[t]); > >> + > >> + zfree(&rec->thread_masks); > >> +} > >> + > >> +static int record__alloc_thread_masks(struct record *rec, int nr_threads, int nr_bits) > >> +{ > >> + int t, ret; > >> + > >> + rec->thread_masks = zalloc(nr_threads * sizeof(*(rec->thread_masks))); > >> + if (!rec->thread_masks) { > >> + pr_err("Failed to allocate thread masks\n"); > >> + return -ENOMEM; > >> + } > >> + > >> + for (t = 0; t < nr_threads; t++) { > >> + ret = record__thread_mask_alloc(&rec->thread_masks[t], nr_bits); > >> + if (ret) { > >> + pr_err("Failed to allocate thread masks[%d]\n", t); > >> + goto out_free; > >> + } > >> + } > >> + > >> + return 0; > >> + > >> +out_free: > >> + record__free_thread_masks(rec, nr_threads); > >> + > >> + return ret; > >> +} > >> + > >> +static int record__init_thread_default_masks(struct record *rec, struct perf_cpu_map *cpus) > >> +{ > >> + int ret; > >> + > >> + ret = record__alloc_thread_masks(rec, 1, cpu__max_cpu().cpu); > >> + if (ret) > >> + return ret; > >> + > >> + record__mmap_cpu_mask_init(&rec->thread_masks->maps, cpus); > >> + > >> + rec->nr_threads = 1; > >> + > >> + return 0; > >> +} > >> + > >> +static int record__init_thread_masks(struct record *rec) > >> +{ > >> + struct perf_cpu_map *cpus = rec->evlist->core.cpus; > >> + > >> + return record__init_thread_default_masks(rec, cpus); > >> +} > >> + > >> int cmd_record(int argc, const char **argv) > >> { > >> int err; > >> @@ -2948,6 +3063,12 @@ int cmd_record(int argc, const char **argv) > >> goto out; > >> } > >> > >> + err = record__init_thread_masks(rec); > >> + if (err) { > >> + pr_err("Failed to initialize parallel data streaming masks\n"); > >> + goto out; > >> + } > >> + > >> if (rec->opts.nr_cblocks > nr_cblocks_max) > >> rec->opts.nr_cblocks = nr_cblocks_max; > >> pr_debug("nr_cblocks: %d\n", rec->opts.nr_cblocks); > >> @@ -2966,6 +3087,8 @@ int cmd_record(int argc, const char **argv) > >> symbol__exit(); > >> auxtrace_record__free(rec->itr); > >> out_opts: > >> + record__free_thread_masks(rec, rec->nr_threads); > >> + rec->nr_threads = 0; > >> evlist__close_control(rec->opts.ctl_fd, rec->opts.ctl_fd_ack, &rec->opts.ctl_fd_close); > >> return err; > >> } > >> -- > >> 2.19.0 > >>
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