Turbostat: Fix sched affinity mess

[collectd.git] / src / turbostat.c

diff --git a/src/turbostat.c b/src/turbostat.c
index 111eed2..ecc2375 100644 (file)
--- a/src/turbostat.c
+++ b/src/turbostat.c
@@ -102,8 +102,8 @@ static double rapl_energy_units;
 int aperf_mperf_unstable;
 int backwards_count;
 
-cpu_set_t *cpu_present_set, *cpu_affinity_set;
-size_t cpu_present_setsize, cpu_affinity_setsize;
+cpu_set_t *cpu_present_set, *cpu_affinity_set, *cpu_saved_affinity_set;
+size_t cpu_present_setsize, cpu_affinity_setsize, cpu_saved_affinity_setsize;
 
 struct thread_data {
        unsigned long long tsc;
@@ -173,6 +173,7 @@ struct timeval tv_even, tv_odd, tv_delta;
 enum return_values {
        OK = 0,
        ERR_CPU_MIGRATE,
+       ERR_CPU_SAVE_SCHED_AFFINITY,
        ERR_MSR_IA32_APERF,
        ERR_MSR_IA32_MPERF,
        ERR_MSR_SMI_COUNT,
@@ -254,26 +255,25 @@ for_all_cpus(int (func)(struct thread_data *, struct core_data *, struct pkg_dat
 }
 
 static int __attribute__((warn_unused_result))
-cpu_migrate(int cpu)
-{
-       CPU_ZERO_S(cpu_affinity_setsize, cpu_affinity_set);
-       CPU_SET_S(cpu, cpu_affinity_setsize, cpu_affinity_set);
-       if (sched_setaffinity(0, cpu_affinity_setsize, cpu_affinity_set) == -1)
-               return -ERR_CPU_MIGRATE;
-       else
-               return 0;
-}
-
-static int __attribute__((warn_unused_result))
-open_msr(int cpu)
+open_msr(int cpu, _Bool multiple_read)
 {
        char pathname[32];
        int fd;
 
-       /* FIXME: Do we really need this, why? */
-       if (cpu_migrate(cpu)) {
-               ERROR("Could not migrate to CPU %d", cpu);
-               return -ERR_CPU_MIGRATE;
+       /*
+        * If we need to do multiple read, let's migrate to the CPU
+        * Otherwise, we would lose time calling functions on another CPU
+        *
+        * If we are not yet initialized (cpu_affinity_setsize = 0),
+        * we need to skip this optimisation.
+        */
+       if (multiple_read && cpu_affinity_setsize) {
+               CPU_ZERO_S(cpu_affinity_setsize, cpu_affinity_set);
+               CPU_SET_S(cpu, cpu_affinity_setsize, cpu_affinity_set);
+               if (sched_setaffinity(0, cpu_affinity_setsize, cpu_affinity_set) == -1) {
+                       ERROR("Could not migrate to CPU %d", cpu);
+                       return -ERR_CPU_MIGRATE;
+               }
        }
 
        ssnprintf(pathname, sizeof(pathname), "/dev/cpu/%d/msr", cpu);
@@ -303,7 +303,7 @@ get_msr(int cpu, off_t offset, unsigned long long *msr)
        ssize_t retval;
        int fd;
 
-       fd = open_msr(cpu);
+       fd = open_msr(cpu, 0);
        if (fd < 0)
                return fd;
        retval = read_msr(fd, offset, msr);
@@ -446,7 +446,7 @@ get_counters(struct thread_data *t, struct core_data *c, struct pkg_data *p)
        int msr_fd;
        int retval = 0;
 
-       msr_fd = open_msr(cpu);
+       msr_fd = open_msr(cpu, 1);
        if (msr_fd < 0)
                return msr_fd;
 
@@ -553,6 +553,10 @@ free_all_buffers(void)
        cpu_affinity_set = NULL;
        cpu_affinity_setsize = 0;
 
+       CPU_FREE(cpu_saved_affinity_set);
+       cpu_saved_affinity_set = NULL;
+       cpu_saved_affinity_setsize = 0;
+
        free(thread_even);
        free(core_even);
        free(package_even);
@@ -898,37 +902,49 @@ turbostat_read(user_data_t * not_used)
                        return -ERR_CPU_NOT_PRESENT;
        }
 
+       /* Saving the scheduling affinity, as it will be modified by get_counters */
+       if (sched_getaffinity(0, cpu_saved_affinity_setsize, cpu_saved_affinity_set) != 0)
+               return -ERR_CPU_SAVE_SCHED_AFFINITY;
+
        if (!initialized) {
                if ((ret = for_all_cpus(get_counters, EVEN_COUNTERS)) < 0)
-                       return ret;
+                       goto out;
                gettimeofday(&tv_even, (struct timezone *)NULL);
                is_even = 1;
                initialized = 1;
-               return 0;
+               ret = 0;
+               goto out;
        }
 
        if (is_even) {
                if ((ret = for_all_cpus(get_counters, ODD_COUNTERS)) < 0)
-                       return ret;
+                       goto out;
                gettimeofday(&tv_odd, (struct timezone *)NULL);
                is_even = 0;
                timersub(&tv_odd, &tv_even, &tv_delta);
                if ((ret = for_all_cpus_2(delta_cpu, ODD_COUNTERS, EVEN_COUNTERS)) < 0)
-                       return ret;
+                       goto out;
                if ((ret = for_all_cpus(submit_counters, EVEN_COUNTERS)) < 0)
-                       return ret;
+                       goto out;
        } else {
                if ((ret = for_all_cpus(get_counters, EVEN_COUNTERS)) < 0)
-                       return ret;
+                       goto out;
                gettimeofday(&tv_even, (struct timezone *)NULL);
                is_even = 1;
                timersub(&tv_even, &tv_odd, &tv_delta);
                if ((ret = for_all_cpus_2(delta_cpu, EVEN_COUNTERS, ODD_COUNTERS)) < 0)
-                       return ret;
+                       goto out;
                if ((ret = for_all_cpus(submit_counters, ODD_COUNTERS)) < 0)
-                       return ret;
+                       goto out;
        }
-       return 0;
+       ret = 0;
+out:
+       /*
+        * Let's restore the affinity
+        * This might fail if the number of CPU changed, but we can't do anything in that case..
+        */
+       (void)sched_setaffinity(0, cpu_saved_affinity_setsize, cpu_saved_affinity_set);
+       return ret;
 }
 
 static int __attribute__((warn_unused_result))
@@ -1269,6 +1285,19 @@ topology_probe()
 
 
        /*
+        * Allocate and initialize cpu_saved_affinity_set
+        */
+       cpu_saved_affinity_set = CPU_ALLOC((topo.max_cpu_num + 1));
+       if (cpu_saved_affinity_set == NULL) {
+               free(cpus);
+               ERROR("CPU_ALLOC");
+               return -ERR_CPU_ALLOC;
+       }
+       cpu_saved_affinity_setsize = CPU_ALLOC_SIZE((topo.max_cpu_num + 1));
+       CPU_ZERO_S(cpu_saved_affinity_setsize, cpu_saved_affinity_set);
+
+
+       /*
         * For online cpus
         * find max_core_id, max_package_id
         */