a12b51c478
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>
60 lines
1,012 B
C
60 lines
1,012 B
C
#include "util.h"
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#include "../perf.h"
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#include "cpumap.h"
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#include <assert.h>
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#include <stdio.h>
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int cpumap[MAX_NR_CPUS];
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static int default_cpu_map(void)
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{
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int nr_cpus, i;
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nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
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assert(nr_cpus <= MAX_NR_CPUS);
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assert((int)nr_cpus >= 0);
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for (i = 0; i < nr_cpus; ++i)
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cpumap[i] = i;
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return nr_cpus;
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}
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int read_cpu_map(void)
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{
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FILE *onlnf;
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int nr_cpus = 0;
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int n, cpu, prev;
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char sep;
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onlnf = fopen("/sys/devices/system/cpu/online", "r");
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if (!onlnf)
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return default_cpu_map();
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sep = 0;
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prev = -1;
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for (;;) {
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n = fscanf(onlnf, "%u%c", &cpu, &sep);
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if (n <= 0)
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break;
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if (prev >= 0) {
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assert(nr_cpus + cpu - prev - 1 < MAX_NR_CPUS);
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while (++prev < cpu)
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cpumap[nr_cpus++] = prev;
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}
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assert (nr_cpus < MAX_NR_CPUS);
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cpumap[nr_cpus++] = cpu;
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if (n == 2 && sep == '-')
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prev = cpu;
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else
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prev = -1;
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if (n == 1 || sep == '\n')
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break;
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}
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fclose(onlnf);
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if (nr_cpus > 0)
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return nr_cpus;
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return default_cpu_map();
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}
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