@@ -445,14 +445,23 @@ static struct cpu_map *pmu_cpumask(const char *name)
FILE *file;
struct cpu_map *cpus;
const char *sysfs = sysfs__mountpoint();
+ const char *templates[] = {
+ "%s/bus/event_source/devices/%s/cpumask",
+ "%s/bus/event_source/devices/%s/cpus",
+ NULL
+ };
+ const char **template;
if (!sysfs)
return NULL;
- snprintf(path, PATH_MAX,
- "%s/bus/event_source/devices/%s/cpumask", sysfs, name);
+ for (template = templates; *template; template++) {
+ snprintf(path, PATH_MAX, *template, sysfs, name);
+ if (stat(path, &st) == 0)
+ break;
+ }
- if (stat(path, &st) < 0)
+ if (!*template)
return NULL;
file = fopen(path, "r");
The perf tools can read a cpumask file for a PMU, describing a subset of CPUs which that PMU covers. So far this has only been used to cater for uncore PMUs, which in practice happen to only have a single CPU described in the mask. Until recently, the perf tools only correctly handled cpumask containing a single CPU, and only when monitoring in system-wide mode. For example, prior to commit 00e727bb389359c8 ("perf stat: Balance opening and reading events"), a mask with more than a single CPU could cause perf stat to hang. When a CPU PMU covers a subset of CPUs, but lacks a cpumask, perf record will fail to open events (on the cores the PMU does not support), and gives up. For systems with heterogeneous CPUs such as ARM big.LITTLE systems, this presents a problem. We have a PMU for each microarchitecture (e.g. a big PMU and a little PMU), and would like to expose a cpumask for each (so as to allow perf record and other tools to do the right thing). However, doing so kernel-side will cause old perf binaries to not function (e.g. hitting the issue solved by 00e727bb389359c8), and thus commits the cardinal sin of breaking (existing) userspace. To address this chicken-and-egg problem, this patch adds support got a new file, cpus, which is largely identical to the existing cpumask file. A kernel can expose this file, knowing that new perf binaries will correctly support it, while old perf binaries will not look for it (and thus will not be broken). Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: linux-kernel@vger.kernel.org --- tools/perf/util/pmu.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) -- 1.9.1