Messages in this thread Patch in this message | | | From | Arnaldo Carvalho de Melo <> | Subject | [PATCH 2/2] perf evsel: Fix inverted test for fixing up attr.inherit flag | Date | Mon, 21 Feb 2011 22:31:02 -0300 |
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From: Arnaldo Carvalho de Melo <acme@redhat.com>
The kernel refuses mmapping an event with the inherit flag set for something that is systemwide (cpu == -1), and the evsel layer got this reversed at some point, fix it.
The symtom was that the --pid and --tid parameters for 'perf record' and 'perf top' returned with -EINVAL, like:
# /tmp/build-perf/perf record -v -fo/tmp/perf.data -p 1042 Warning: ... trying to fall back to cpu-clock-ticks
Fatal: failed to mmap with 22 (Invalid argument)
Reported-by: David Ahern <dsahern@gmail.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul Mackerras <paulus@samba.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Tom Zanussi <tzanussi@gmail.com> LKML-Reference: <new-submission> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> --- tools/perf/util/evsel.c | 15 +++++++++++++-- 1 files changed, 13 insertions(+), 2 deletions(-)
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c index 63cadaf..8083d51 100644 --- a/tools/perf/util/evsel.c +++ b/tools/perf/util/evsel.c @@ -179,8 +179,19 @@ static int __perf_evsel__open(struct perf_evsel *evsel, struct cpu_map *cpus, for (cpu = 0; cpu < cpus->nr; cpu++) { int group_fd = -1; - - evsel->attr.inherit = (cpus->map[cpu] < 0) && inherit; + /* + * Don't allow mmap() of inherited per-task counters. This + * would create a performance issue due to all children writing + * to the same buffer. + * + * FIXME: + * Proper fix is not to pass 'inherit' to perf_evsel__open*, + * but a 'flags' parameter, with 'group' folded there as well, + * then introduce a PERF_O_{MMAP,GROUP,INHERIT} enum, and if + * O_MMAP is set, emit a warning if cpu < 0 and O_INHERIT is + * set. Lets go for the minimal fix first tho. + */ + evsel->attr.inherit = (cpus->map[cpu] >= 0) && inherit; for (thread = 0; thread < threads->nr; thread++) { -- 1.6.2.5
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