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-top.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) (limited to 'tools/perf/builtin-top.c') diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c index 31f2e59..0b719e3 100644 --- a/tools/perf/builtin-top.c +++ b/tools/perf/builtin-top.c @@ -28,6 +28,7 @@ #include #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) { -- cgit v1.1