cpupower: Better detect offlined CPUs
Thomas Renninger [Thu, 11 Aug 2011 23:11:37 +0000 (01:11 +0200)]
Before, checking for offlined CPUs was done dirty and
it was checked whether topology parsing returned -1 values.
But this is a valid case on a Xen (and possibly other) kernels.

Do proper online/offline checking, also take CONFIG_HOTPLUG_CPU
option into account (no /sys/devices/../cpuX/online file).

Signed-off-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>

tools/power/cpupower/utils/helpers/helpers.h
tools/power/cpupower/utils/helpers/sysfs.c
tools/power/cpupower/utils/helpers/sysfs.h
tools/power/cpupower/utils/helpers/topology.c
tools/power/cpupower/utils/idle_monitor/cpupower-monitor.c

index 592ee36..7a83022 100644 (file)
@@ -96,6 +96,9 @@ struct cpupower_topology {
                int pkg;
                int core;
                int cpu;
+
+               /* flags */
+               unsigned int is_online:1;
        } *core_info;
 };
 
index 55e2466..c634302 100644 (file)
@@ -56,6 +56,56 @@ static unsigned int sysfs_write_file(const char *path,
        return (unsigned int) numwrite;
 }
 
+/*
+ * Detect whether a CPU is online
+ *
+ * Returns:
+ *     1 -> if CPU is online
+ *     0 -> if CPU is offline
+ *     negative errno values in error case
+ */
+int sysfs_is_cpu_online(unsigned int cpu)
+{
+       char path[SYSFS_PATH_MAX];
+       int fd;
+       ssize_t numread;
+       unsigned long long value;
+       char linebuf[MAX_LINE_LEN];
+       char *endp;
+       struct stat statbuf;
+
+       snprintf(path, sizeof(path), PATH_TO_CPU "cpu%u", cpu);
+
+       if (stat(path, &statbuf) != 0)
+               return 0;
+
+       /*
+        * kernel without CONFIG_HOTPLUG_CPU
+        * -> cpuX directory exists, but not cpuX/online file
+        */
+       snprintf(path, sizeof(path), PATH_TO_CPU "cpu%u/online", cpu);
+       if (stat(path, &statbuf) != 0)
+               return 1;
+
+       fd = open(path, O_RDONLY);
+       if (fd == -1)
+               return -errno;
+
+       numread = read(fd, linebuf, MAX_LINE_LEN - 1);
+       if (numread < 1) {
+               close(fd);
+               return -EIO;
+       }
+       linebuf[numread] = '\0';
+       close(fd);
+
+       value = strtoull(linebuf, &endp, 0);
+       if (value > 1 || value < 0)
+               return -EINVAL;
+
+       return value;
+}
+
 /* CPUidle idlestate specific /sys/devices/system/cpu/cpuX/cpuidle/ access */
 
 /*
index f9373e0..8cb797b 100644 (file)
@@ -7,6 +7,8 @@
 
 extern unsigned int sysfs_read_file(const char *path, char *buf, size_t buflen);
 
+extern int sysfs_is_cpu_online(unsigned int cpu);
+
 extern unsigned long sysfs_get_idlestate_latency(unsigned int cpu,
                                                unsigned int idlestate);
 extern unsigned long sysfs_get_idlestate_usage(unsigned int cpu,
index 385ee5c..4eae2c4 100644 (file)
@@ -41,6 +41,8 @@ struct cpuid_core_info {
        unsigned int pkg;
        unsigned int thread;
        unsigned int cpu;
+       /* flags */
+       unsigned int is_online:1;
 };
 
 static int __compare(const void *t1, const void *t2)
@@ -78,6 +80,8 @@ int get_cpu_topology(struct cpupower_topology *cpu_top)
                return -ENOMEM;
        cpu_top->pkgs = cpu_top->cores = 0;
        for (cpu = 0; cpu < cpus; cpu++) {
+               cpu_top->core_info[cpu].cpu = cpu;
+               cpu_top->core_info[cpu].is_online = sysfs_is_cpu_online(cpu);
                cpu_top->core_info[cpu].pkg =
                        sysfs_topology_read_file(cpu, "physical_package_id");
                if ((int)cpu_top->core_info[cpu].pkg != -1 &&
@@ -85,7 +89,6 @@ int get_cpu_topology(struct cpupower_topology *cpu_top)
                        cpu_top->pkgs = cpu_top->core_info[cpu].pkg;
                cpu_top->core_info[cpu].core =
                        sysfs_topology_read_file(cpu, "core_id");
-               cpu_top->core_info[cpu].cpu = cpu;
        }
        cpu_top->pkgs++;
 
index ba4bf06..dd8e1ea 100644 (file)
@@ -190,9 +190,13 @@ void print_results(int topology_depth, int cpu)
                        }
                }
        }
-       /* cpu offline */
-       if (cpu_top.core_info[cpu].pkg == -1 ||
-           cpu_top.core_info[cpu].core == -1) {
+       /*
+        * The monitor could still provide useful data, for example
+        * AMD HW counters partly sit in PCI config space.
+        * It's up to the monitor plug-in to check .is_online, this one
+        * is just for additional info.
+        */
+       if (!cpu_top.core_info[cpu].is_online) {
                printf(_(" *is offline\n"));
                return;
        } else