From a12b51c478899fe0b7e874a559b05ba35f1128ee Mon Sep 17 00:00:00 2001 From: Paul Mackerras Date: Wed, 10 Mar 2010 20:36:09 +1100 Subject: perf tools: Fix sparse CPU numbering related bugs At present, the perf subcommands that do system-wide monitoring (perf stat, perf record and perf top) don't work properly unless the online cpus are numbered 0, 1, ..., N-1. These tools ask for the number of online cpus with sysconf(_SC_NPROCESSORS_ONLN) and then try to create events for cpus 0, 1, ..., N-1. This creates problems for systems where the online cpus are numbered sparsely. For example, a POWER6 system in single-threaded mode (i.e. only running 1 hardware thread per core) will have only even-numbered cpus online. This fixes the problem by reading the /sys/devices/system/cpu/online file to find out which cpus are online. The code that does that is in tools/perf/util/cpumap.[ch], and consists of a read_cpu_map() function that sets up a cpumap[] array and returns the number of online cpus. If /sys/devices/system/cpu/online can't be read or can't be parsed successfully, it falls back to using sysconf to ask how many cpus are online and sets up an identity map in cpumap[]. The perf record, perf stat and perf top code then calls read_cpu_map() in the system-wide monitoring case (instead of sysconf) and uses cpumap[] to get the cpu numbers to pass to perf_event_open. Signed-off-by: Paul Mackerras Cc: Anton Blanchard Cc: Peter Zijlstra Cc: Arnaldo Carvalho de Melo LKML-Reference: <20100310093609.GA3959@brick.ozlabs.ibm.com> Signed-off-by: Ingo Molnar --- tools/perf/builtin-stat.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) (limited to 'tools/perf/builtin-stat.c') diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c index e8c85d5aec41..95db31cff6fd 100644 --- a/tools/perf/builtin-stat.c +++ b/tools/perf/builtin-stat.c @@ -45,6 +45,7 @@ #include "util/event.h" #include "util/debug.h" #include "util/header.h" +#include "util/cpumap.h" #include #include @@ -151,7 +152,7 @@ static void create_perf_stat_counter(int counter, int pid) unsigned int cpu; for (cpu = 0; cpu < nr_cpus; cpu++) { - fd[cpu][counter] = sys_perf_event_open(attr, -1, cpu, -1, 0); + fd[cpu][counter] = sys_perf_event_open(attr, -1, cpumap[cpu], -1, 0); if (fd[cpu][counter] < 0 && verbose) fprintf(stderr, ERR_PERF_OPEN, counter, fd[cpu][counter], strerror(errno)); @@ -519,9 +520,10 @@ int cmd_stat(int argc, const char **argv, const char *prefix __used) nr_counters = ARRAY_SIZE(default_attrs); } - nr_cpus = sysconf(_SC_NPROCESSORS_ONLN); - assert(nr_cpus <= MAX_NR_CPUS); - assert((int)nr_cpus >= 0); + if (system_wide) + nr_cpus = read_cpu_map(); + else + nr_cpus = 1; /* * We dont want to block the signals - that would cause -- cgit v1.2.3