Commit a12b51c4 authored by Paul Mackerras's avatar Paul Mackerras Committed by Ingo Molnar
Browse files

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: default avatarPaul 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: default avatarIngo Molnar <mingo@elte.hu>
parent 220b140b

tools/perf/Makefile

+2 −0
Original line number Diff line number Diff line
@@ -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

tools/perf/builtin-record.c

+3 −4
Original line number Diff line number Diff line
@@ -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) {

tools/perf/builtin-stat.c

+6 −4
Original line number Diff line number Diff line
@@ -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

tools/perf/builtin-top.c

+4 −5
Original line number Diff line number Diff line
@@ -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) {

tools/perf/util/cpumap.c

0 → 100644
+59 −0
Original line number Diff line number Diff line 
#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();

}

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