Messages in this thread Patch in this message | | | From | Jin Yao <> | Subject | [PATCH] perf evsel: Get group fd from CPU0 for system wide event | Date | Thu, 30 Apr 2020 09:34:51 +0800 |
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A metric may consist of system wide event and non system-wide event. The event group leader may be the system wide event.
For example, the metric "C2_Pkg_Residency" consists of "cstate_pkg/c2-residency" and "msr/tsc". The former counts on the first CPU of socket (tagged system-wide) and the latter is per CPU.
But "C2_Pkg_Residency" hits assertion failure on cascadelakex.
# perf stat -M "C2_Pkg_Residency" -a -- sleep 1 perf: util/evsel.c:1464: get_group_fd: Assertion `!(fd == -1)' failed. Aborted
get_group_fd(evsel, cpu, thread) { leader = evsel->leader; fd = FD(leader, cpu, thread); BUG_ON(fd == -1); }
Considering this case, leader is "cstate_pkg/c2-residency", evsel is "msr/tsc" and cpu is 1. Because "cstate_pkg/c2-residency" is a system-wide event and it's processed on CPU0, so FD(leader, 1, thread) must return an invalid fd, then BUG_ON() may be triggered.
This patch gets group fd from CPU0 for system wide event if FD(leader, cpu, thread) returns invalid fd.
With this patch,
# perf stat -M "C2_Pkg_Residency" -a -- sleep 1
Performance counter stats for 'system wide':
1000850802 cstate_pkg/c2-residency/ # 0.5 C2_Pkg_Residency 201446161592 msr/tsc/
1.010637051 seconds time elapsed
Fixes: 6a4bb04caacc ("perf tools: Enable grouping logic for parsed events") Signed-off-by: Jin Yao <yao.jin@linux.intel.com> --- tools/perf/util/evsel.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c index 6a571d322bb2..cd6470f63d6f 100644 --- a/tools/perf/util/evsel.c +++ b/tools/perf/util/evsel.c @@ -1461,6 +1461,9 @@ static int get_group_fd(struct evsel *evsel, int cpu, int thread) BUG_ON(!leader->core.fd); fd = FD(leader, cpu, thread); + if (fd == -1 && leader->core.system_wide) + fd = FD(leader, 0, thread); + BUG_ON(fd == -1); return fd; -- 2.17.1
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