Messages in this thread Patch in this message | | | From | Ian Rogers <> | Date | Mon, 4 Apr 2022 15:25:52 -0700 | Subject | Re: [PATCH v13 01/16] perf record: Introduce thread affinity and mmap masks |
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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 > defines CPUs that a thread is allowed to run on. Thread maps > mask defines mmap data buffers the thread serves to stream > profiling data from. > > Acked-by: Andi Kleen <ak@linux.intel.com> > Acked-by: Namhyung Kim <namhyung@gmail.com> > Reviewed-by: Riccardo Mancini <rickyman7@gmail.com> > Tested-by: Riccardo Mancini <rickyman7@gmail.com> > Signed-off-by: Alexey Bayduraev <alexey.v.bayduraev@linux.intel.com> > --- > tools/perf/builtin-record.c | 123 ++++++++++++++++++++++++++++++++++++ > 1 file changed, 123 insertions(+) > > diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c > index bb716c953d02..41998f2140cd 100644 > --- a/tools/perf/builtin-record.c > +++ b/tools/perf/builtin-record.c > @@ -87,6 +87,11 @@ struct switch_output { > int cur_file; > }; > > +struct thread_mask { > + struct mmap_cpu_mask maps; > + struct mmap_cpu_mask affinity; > +}; > + > struct record { > struct perf_tool tool; > struct record_opts opts; > @@ -112,6 +117,8 @@ struct record { > struct mmap_cpu_mask affinity_mask; > unsigned long output_max_size; /* = 0: unlimited */ > struct perf_debuginfod debuginfod; > + int nr_threads; > + struct thread_mask *thread_masks; > }; > > static volatile int done; > @@ -2204,6 +2211,47 @@ static int record__parse_affinity(const struct option *opt, const char *str, int > return 0; > } > > +static int record__mmap_cpu_mask_alloc(struct mmap_cpu_mask *mask, int nr_bits) > +{ > + mask->nbits = nr_bits; > + mask->bits = bitmap_zalloc(mask->nbits); > + if (!mask->bits) > + return -ENOMEM; > + > + return 0; > +} > + > +static void record__mmap_cpu_mask_free(struct mmap_cpu_mask *mask) > +{ > + bitmap_free(mask->bits); > + mask->nbits = 0; > +} > + > +static int record__thread_mask_alloc(struct thread_mask *mask, int nr_bits) > +{ > + int ret; > + > + ret = record__mmap_cpu_mask_alloc(&mask->maps, nr_bits); > + if (ret) { > + mask->affinity.bits = NULL; > + return ret; > + } > + > + ret = record__mmap_cpu_mask_alloc(&mask->affinity, nr_bits); > + if (ret) { > + record__mmap_cpu_mask_free(&mask->maps); > + mask->maps.bits = NULL; > + } > + > + return ret; > +} > + > +static void record__thread_mask_free(struct thread_mask *mask) > +{ > + record__mmap_cpu_mask_free(&mask->maps); > + record__mmap_cpu_mask_free(&mask->affinity); > +} > + > static int parse_output_max_size(const struct option *opt, > const char *str, int unset) > { > @@ -2683,6 +2731,73 @@ static struct option __record_options[] = { > > struct option *record_options = __record_options; > > +static void record__mmap_cpu_mask_init(struct mmap_cpu_mask *mask, struct perf_cpu_map *cpus) > +{ > + int c; > + for (c = 0; c < cpus->nr; c++) > + set_bit(cpus->map[c].cpu, mask->bits); > +} > +
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
> +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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