path: root/tools/perf/builtin-top.c
diff options
authorPaul Mackerras <paulus@samba.org>2010-03-10 20:36:09 +1100
committerIngo Molnar <mingo@elte.hu>2010-03-11 13:36:53 +0100
commita12b51c478899fe0b7e874a559b05ba35f1128ee (patch)
tree25b9911c1932c13fd8b468aa18eb17982ba31b59 /tools/perf/builtin-top.c
parent220b140b52ab6cc133f674a7ffec8fa792054f25 (diff)
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 <paulus@samba.org> Cc: Anton Blanchard <anton@samba.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> LKML-Reference: <20100310093609.GA3959@brick.ozlabs.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'tools/perf/builtin-top.c')
1 files changed, 4 insertions, 5 deletions
diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index 31f2e597800..0b719e3dde0 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -28,6 +28,7 @@
#include <linux/rbtree.h>
#include "util/parse-options.h"
#include "util/parse-events.h"
+#include "util/cpumap.h"
#include "util/debug.h"
@@ -1123,7 +1124,7 @@ static void start_counter(int i, int counter)
cpu = profile_cpu;
if (target_pid == -1 && profile_cpu == -1)
- cpu = i;
+ cpu = cpumap[i];
attr = attrs + counter;
@@ -1347,12 +1348,10 @@ int cmd_top(int argc, const char **argv, const char *prefix __used)
attrs[counter].sample_period = default_interval;
- nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
- assert(nr_cpus <= MAX_NR_CPUS);
- assert(nr_cpus >= 0);
if (target_pid != -1 || profile_cpu != -1)
nr_cpus = 1;
+ else
+ nr_cpus = read_cpu_map();
if (print_entries == 0) {