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.h | 7 +++++++ 1 file changed, 7 insertions(+) create mode 100644 tools/perf/util/cpumap.h (limited to 'tools/perf/util/cpumap.h') diff --git a/tools/perf/util/cpumap.h b/tools/perf/util/cpumap.h new file mode 100644 index 000000000000..86c78bb33098 --- /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 */ -- cgit v1.2.3-59-g8ed1b