diff options
author | Adrian Hunter <adrian.hunter@intel.com> | 2022-09-05 14:42:09 +0300 |
---|---|---|
committer | Arnaldo Carvalho de Melo <acme@redhat.com> | 2022-09-08 18:17:22 +0300 |
commit | 7864d8f7c088aad988c44c631f1ceed9179cf2cf (patch) | |
tree | 6d4d7abf13477623872a882dad25aa72414d70d7 | |
parent | 4efa8e314351cb3e7f229ddd3571069edf38f99a (diff) |
libperf evlist: Fix per-thread mmaps for multi-threaded targets
The offending commit removed mmap_per_thread(), which did not consider
the different set-output rules for per-thread mmaps i.e. in the per-thread
case set-output is used for file descriptors of the same thread not the
same cpu.
This was not immediately noticed because it only happens with
multi-threaded targets and we do not have a test for that yet.
Reinstate mmap_per_thread() expanding it to cover also system-wide per-cpu
events i.e. to continue to allow the mixing of per-thread and per-cpu
mmaps.
Debug messages (with -vv) show the file descriptors that are opened with
sys_perf_event_open. New debug messages are added (needs -vvv) that show
also which file descriptors are mmapped and which are redirected with
set-output.
In the per-cpu case (cpu != -1) file descriptors for the same CPU are
set-output to the first file descriptor for that CPU.
In the per-thread case (cpu == -1) file descriptors for the same thread are
set-output to the first file descriptor for that thread.
Example (process 17489 has 2 threads):
Before (but with new debug prints):
$ perf record --no-bpf-event -vvv --per-thread -p 17489
<SNIP>
sys_perf_event_open: pid 17489 cpu -1 group_fd -1 flags 0x8 = 5
sys_perf_event_open: pid 17490 cpu -1 group_fd -1 flags 0x8 = 6
<SNIP>
libperf: idx 0: mmapping fd 5
libperf: idx 0: set output fd 6 -> 5
failed to mmap with 22 (Invalid argument)
After:
$ perf record --no-bpf-event -vvv --per-thread -p 17489
<SNIP>
sys_perf_event_open: pid 17489 cpu -1 group_fd -1 flags 0x8 = 5
sys_perf_event_open: pid 17490 cpu -1 group_fd -1 flags 0x8 = 6
<SNIP>
libperf: mmap_per_thread: nr cpu values (may include -1) 1 nr threads 2
libperf: idx 0: mmapping fd 5
libperf: idx 1: mmapping fd 6
<SNIP>
[ perf record: Woken up 2 times to write data ]
[ perf record: Captured and wrote 0.018 MB perf.data (15 samples) ]
Per-cpu example (process 20341 has 2 threads, same as above):
$ perf record --no-bpf-event -vvv -p 20341
<SNIP>
sys_perf_event_open: pid 20341 cpu 0 group_fd -1 flags 0x8 = 5
sys_perf_event_open: pid 20342 cpu 0 group_fd -1 flags 0x8 = 6
sys_perf_event_open: pid 20341 cpu 1 group_fd -1 flags 0x8 = 7
sys_perf_event_open: pid 20342 cpu 1 group_fd -1 flags 0x8 = 8
sys_perf_event_open: pid 20341 cpu 2 group_fd -1 flags 0x8 = 9
sys_perf_event_open: pid 20342 cpu 2 group_fd -1 flags 0x8 = 10
sys_perf_event_open: pid 20341 cpu 3 group_fd -1 flags 0x8 = 11
sys_perf_event_open: pid 20342 cpu 3 group_fd -1 flags 0x8 = 12
sys_perf_event_open: pid 20341 cpu 4 group_fd -1 flags 0x8 = 13
sys_perf_event_open: pid 20342 cpu 4 group_fd -1 flags 0x8 = 14
sys_perf_event_open: pid 20341 cpu 5 group_fd -1 flags 0x8 = 15
sys_perf_event_open: pid 20342 cpu 5 group_fd -1 flags 0x8 = 16
sys_perf_event_open: pid 20341 cpu 6 group_fd -1 flags 0x8 = 17
sys_perf_event_open: pid 20342 cpu 6 group_fd -1 flags 0x8 = 18
sys_perf_event_open: pid 20341 cpu 7 group_fd -1 flags 0x8 = 19
sys_perf_event_open: pid 20342 cpu 7 group_fd -1 flags 0x8 = 20
<SNIP>
libperf: mmap_per_cpu: nr cpu values 8 nr threads 2
libperf: idx 0: mmapping fd 5
libperf: idx 0: set output fd 6 -> 5
libperf: idx 1: mmapping fd 7
libperf: idx 1: set output fd 8 -> 7
libperf: idx 2: mmapping fd 9
libperf: idx 2: set output fd 10 -> 9
libperf: idx 3: mmapping fd 11
libperf: idx 3: set output fd 12 -> 11
libperf: idx 4: mmapping fd 13
libperf: idx 4: set output fd 14 -> 13
libperf: idx 5: mmapping fd 15
libperf: idx 5: set output fd 16 -> 15
libperf: idx 6: mmapping fd 17
libperf: idx 6: set output fd 18 -> 17
libperf: idx 7: mmapping fd 19
libperf: idx 7: set output fd 20 -> 19
<SNIP>
[ perf record: Woken up 7 times to write data ]
[ perf record: Captured and wrote 0.020 MB perf.data (17 samples) ]
Fixes: ae4f8ae16a078964 ("libperf evlist: Allow mixing per-thread and per-cpu mmaps")
Reported-by: Tomáš Trnka <trnka@scm.com>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=216441
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220905114209.8389-1-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
-rw-r--r-- | tools/lib/perf/evlist.c | 50 |
1 files changed, 50 insertions, 0 deletions
diff --git a/tools/lib/perf/evlist.c b/tools/lib/perf/evlist.c index e6c98a6e3908..6b1bafe267a4 100644 --- a/tools/lib/perf/evlist.c +++ b/tools/lib/perf/evlist.c @@ -486,6 +486,7 @@ mmap_per_evsel(struct perf_evlist *evlist, struct perf_evlist_mmap_ops *ops, if (ops->idx) ops->idx(evlist, evsel, mp, idx); + pr_debug("idx %d: mmapping fd %d\n", idx, *output); if (ops->mmap(map, mp, *output, evlist_cpu) < 0) return -1; @@ -494,6 +495,7 @@ mmap_per_evsel(struct perf_evlist *evlist, struct perf_evlist_mmap_ops *ops, if (!idx) perf_evlist__set_mmap_first(evlist, map, overwrite); } else { + pr_debug("idx %d: set output fd %d -> %d\n", idx, fd, *output); if (ioctl(fd, PERF_EVENT_IOC_SET_OUTPUT, *output) != 0) return -1; @@ -520,6 +522,48 @@ mmap_per_evsel(struct perf_evlist *evlist, struct perf_evlist_mmap_ops *ops, } static int +mmap_per_thread(struct perf_evlist *evlist, struct perf_evlist_mmap_ops *ops, + struct perf_mmap_param *mp) +{ + int nr_threads = perf_thread_map__nr(evlist->threads); + int nr_cpus = perf_cpu_map__nr(evlist->all_cpus); + int cpu, thread, idx = 0; + int nr_mmaps = 0; + + pr_debug("%s: nr cpu values (may include -1) %d nr threads %d\n", + __func__, nr_cpus, nr_threads); + + /* per-thread mmaps */ + for (thread = 0; thread < nr_threads; thread++, idx++) { + int output = -1; + int output_overwrite = -1; + + if (mmap_per_evsel(evlist, ops, idx, mp, 0, thread, &output, + &output_overwrite, &nr_mmaps)) + goto out_unmap; + } + + /* system-wide mmaps i.e. per-cpu */ + for (cpu = 1; cpu < nr_cpus; cpu++, idx++) { + int output = -1; + int output_overwrite = -1; + + if (mmap_per_evsel(evlist, ops, idx, mp, cpu, 0, &output, + &output_overwrite, &nr_mmaps)) + goto out_unmap; + } + + if (nr_mmaps != evlist->nr_mmaps) + pr_err("Miscounted nr_mmaps %d vs %d\n", nr_mmaps, evlist->nr_mmaps); + + return 0; + +out_unmap: + perf_evlist__munmap(evlist); + return -1; +} + +static int mmap_per_cpu(struct perf_evlist *evlist, struct perf_evlist_mmap_ops *ops, struct perf_mmap_param *mp) { @@ -528,6 +572,8 @@ mmap_per_cpu(struct perf_evlist *evlist, struct perf_evlist_mmap_ops *ops, int nr_mmaps = 0; int cpu, thread; + pr_debug("%s: nr cpu values %d nr threads %d\n", __func__, nr_cpus, nr_threads); + for (cpu = 0; cpu < nr_cpus; cpu++) { int output = -1; int output_overwrite = -1; @@ -569,6 +615,7 @@ int perf_evlist__mmap_ops(struct perf_evlist *evlist, struct perf_evlist_mmap_ops *ops, struct perf_mmap_param *mp) { + const struct perf_cpu_map *cpus = evlist->all_cpus; struct perf_evsel *evsel; if (!ops || !ops->get || !ops->mmap) @@ -588,6 +635,9 @@ int perf_evlist__mmap_ops(struct perf_evlist *evlist, if (evlist->pollfd.entries == NULL && perf_evlist__alloc_pollfd(evlist) < 0) return -ENOMEM; + if (perf_cpu_map__empty(cpus)) + return mmap_per_thread(evlist, ops, mp); + return mmap_per_cpu(evlist, ops, mp); } |