Messages in this thread Patch in this message | | | Date | Sat, 3 Sep 2022 10:14:25 +0300 | Subject | Re: perf top -p broken for multithreaded processes since 5.19 | From | Adrian Hunter <> |
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On 2/09/22 22:17, Arnaldo Carvalho de Melo wrote: > Em Fri, Sep 02, 2022 at 05:50:22PM +0300, Adrian Hunter escreveu: >> On 2/09/22 17:46, Tomáš Trnka wrote: >>> Hello, >>> >>> A bug in perf v5.19 and newer completely breaks monitoring multithreaded >>> processes using "perf top -p". The tool fails to start with "Failed to mmap >>> with 22 (Invalid argument)". It still seems to work fine on single-threaded >>> processes. "perf record" is also unaffected. >> >> It has been reported here: >> >> https://bugzilla.kernel.org/show_bug.cgi?id=216441 > > If I do: > > ⬢[acme@toolbox perf-urgent]$ git log -2 > commit dfeb0bc60782471c293938e71b1a1117cfac2cb3 (HEAD -> perf/urgent) > Author: Arnaldo Carvalho de Melo <acme@redhat.com> > Date: Fri Sep 2 16:15:39 2022 -0300 > > Revert "libperf evlist: Check nr_mmaps is correct" > > This reverts commit 4ce47d842d4c16c07b135b8a7975b8f0672bcc0e. > > Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> > > commit 78cd283f6b8ab701cb35eafd5af8140560a88f16 > Author: Arnaldo Carvalho de Melo <acme@redhat.com> > Date: Fri Sep 2 16:13:41 2022 -0300 > > Revert "libperf evlist: Allow mixing per-thread and per-cpu mmaps" > > This reverts commit ae4f8ae16a07896403c90305d4b9be27f657c1fc. > > Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> > ⬢[acme@toolbox perf-urgent]$ > > It works again, Tomáš can you please try doing this to see if this works > for you? >
This is the fix I have so far. I would like to test it some more though.
From: Adrian Hunter <adrian.hunter@intel.com> Date: Sat, 3 Sep 2022 10:05:08 +0300 Subject: [PATCH] libperf evlist: Fix per-thread mmaps for multi-threaded targets
Offending commit did not consider the different set-output rules for per-thread mmaps i.e. in the per-thread case set-output is used for mmaps 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.
Fixes: ae4f8ae16a07 ("libperf evlist: Allow mixing per-thread and per-cpu mmaps") Signed-off-by: Adrian Hunter <adrian.hunter@intel.com> --- tools/lib/perf/evlist.c | 49 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 49 insertions(+)
diff --git a/tools/lib/perf/evlist.c b/tools/lib/perf/evlist.c index e6c98a6e3908e..24280c887520c 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; @@ -519,6 +521,47 @@ mmap_per_evsel(struct perf_evlist *evlist, struct perf_evlist_mmap_ops *ops, return 0; } +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 +571,8 @@ 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 +614,7 @@ 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 +634,9 @@ 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); } -- 2.34.1
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