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>
This commit is contained in:
Paul Mackerras 2010-03-10 20:36:09 +11:00 committed by Ingo Molnar
parent 220b140b52
commit a12b51c478
6 changed files with 81 additions and 13 deletions

View File

@ -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

View File

@ -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) {

View File

@ -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

View File

@ -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) {

59
tools/perf/util/cpumap.c Normal file
View File

@ -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();
}

7
tools/perf/util/cpumap.h Normal file
View File

@ -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 */