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/util/cpumap.c | 59 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 59 insertions(+) create mode 100644 tools/perf/util/cpumap.c (limited to 'tools/perf/util/cpumap.c') diff --git a/tools/perf/util/cpumap.c b/tools/perf/util/cpumap.c new file mode 100644 index 000000000000..4e01490e51e5 --- /dev/null +++ b/tools/perf/util/cpumap.c @@ -0,0 +1,59 @@ +#include "util.h" +#include "../perf.h" +#include "cpumap.h" +#include +#include + +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(); +} -- cgit v1.2.3