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>

diff --git a/tools/perf/Makefile b/tools/perf/Makefile
index 2d537382c68602fa72e4b9dec7f30c20a208aec2..5840499e2d22ce7e7f50c63a422f8fdba39ddf59 100644 (file)
--- a/tools/perf/Makefile
+++ b/tools/perf/Makefile
@@ -387,6 +387,7 @@ LIB_H += util/thread.h
 LIB_H += util/trace-event.h
 LIB_H += util/probe-finder.h
 LIB_H += util/probe-event.h
+LIB_H += util/cpumap.h
 
 LIB_OBJS += util/abspath.o
 LIB_OBJS += util/alias.o
@@ -433,6 +434,7 @@ LIB_OBJS += util/sort.o
 LIB_OBJS += util/hist.o
 LIB_OBJS += util/probe-event.o
 LIB_OBJS += util/util.o
+LIB_OBJS += util/cpumap.o
 
 BUILTIN_OBJS += builtin-annotate.o
 

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index f573bbb8357276d04a1f5fc6f6941f1c63a03183..b09d3b27ca14683a935d3227819477d227899bc0 100644 (file)
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -22,6 +22,7 @@
 #include "util/debug.h"
 #include "util/session.h"
 #include "util/symbol.h"
+#include "util/cpumap.h"
 
 #include <unistd.h>
 #include <sched.h>
@@ -421,9 +422,6 @@ static int __cmd_record(int argc, const char **argv)
        char buf;
 
        page_size = sysconf(_SC_PAGE_SIZE);
-       nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
-       assert(nr_cpus <= MAX_NR_CPUS);
-       assert(nr_cpus >= 0);
 
        atexit(sig_atexit);
        signal(SIGCHLD, sig_handler);
@@ -547,8 +545,9 @@ static int __cmd_record(int argc, const char **argv)
        if ((!system_wide && !inherit) || profile_cpu != -1) {
                open_counters(profile_cpu, target_pid);
        } else {
+               nr_cpus = read_cpu_map();
                for (i = 0; i < nr_cpus; i++)
-                       open_counters(i, target_pid);
+                       open_counters(cpumap[i], target_pid);
        }
 
        if (file_new) {

diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index e8c85d5aec4151fc965f2b16063c60da456d6e67..95db31cff6fdbb63e714dc0725998d7ef76103ea 100644 (file)
--- 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 <sys/prctl.h>
 #include <math.h>
@@ -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

diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index 31f2e597800c7f4331a9aa97ec9045f04a52306b..0b719e3dde050611c282b0c21dccbd91f507ad70 100644 (file)
--- 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();
 
        get_term_dimensions(&winsize);
        if (print_entries == 0) {

diff --git a/tools/perf/util/cpumap.c b/tools/perf/util/cpumap.c
new file mode 100644 (file)
index 0000000..4e01490
--- /dev/null
+++ b/tools/perf/util/cpumap.c
@@ -0,0 +1,59 @@
+#include "util.h"
+#include "../perf.h"
+#include "cpumap.h"
+#include <assert.h>
+#include <stdio.h>
+
+int cpumap[MAX_NR_CPUS];
+
+static int default_cpu_map(void)
+{
+       int nr_cpus, i;
+
+       nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
+       assert(nr_cpus <= MAX_NR_CPUS);
+       assert((int)nr_cpus >= 0);
+
+       for (i = 0; i < nr_cpus; ++i)
+               cpumap[i] = i;
+
+       return nr_cpus;
+}
+
+int read_cpu_map(void)
+{
+       FILE *onlnf;
+       int nr_cpus = 0;
+       int n, cpu, prev;
+       char sep;
+
+       onlnf = fopen("/sys/devices/system/cpu/online", "r");
+       if (!onlnf)
+               return default_cpu_map();
+
+       sep = 0;
+       prev = -1;
+       for (;;) {
+               n = fscanf(onlnf, "%u%c", &cpu, &sep);
+               if (n <= 0)
+                       break;
+               if (prev >= 0) {
+                       assert(nr_cpus + cpu - prev - 1 < MAX_NR_CPUS);
+                       while (++prev < cpu)
+                               cpumap[nr_cpus++] = prev;
+               }
+               assert (nr_cpus < MAX_NR_CPUS);
+               cpumap[nr_cpus++] = cpu;
+               if (n == 2 && sep == '-')
+                       prev = cpu;
+               else
+                       prev = -1;
+               if (n == 1 || sep == '\n')
+                       break;
+       }
+       fclose(onlnf);
+       if (nr_cpus > 0)
+               return nr_cpus;
+
+       return default_cpu_map();
+}

diff --git a/tools/perf/util/cpumap.h b/tools/perf/util/cpumap.h
new file mode 100644 (file)
index 0000000..86c78bb
--- /dev/null
+++ b/tools/perf/util/cpumap.h
@@ -0,0 +1,7 @@
+#ifndef __PERF_CPUMAP_H
+#define __PERF_CPUMAP_H
+
+extern int read_cpu_map(void);
+extern int cpumap[];
+
+#endif /* __PERF_CPUMAP_H */