-
-/*
- * Average offset over two calls to cpu_clock() with a gettimeofday()
- * in the middle
- */
-static void blk_check_time(unsigned long long *t, int this_cpu)
-{
- unsigned long long a, b;
- struct timeval tv;
-
- a = cpu_clock(this_cpu);
- do_gettimeofday(&tv);
- b = cpu_clock(this_cpu);
-
- *t = tv.tv_sec * 1000000000 + tv.tv_usec * 1000;
- *t -= (a + b) / 2;
-}
-
-/*
- * calibrate our inter-CPU timings
- */
-static void blk_trace_check_cpu_time(void *data)
-{
- unsigned long long *t;
- int this_cpu = get_cpu();
-
- t = &per_cpu(blk_trace_cpu_offset, this_cpu);
-
- /*
- * Just call it twice, hopefully the second call will be cache hot
- * and a little more precise
- */
- blk_check_time(t, this_cpu);
- blk_check_time(t, this_cpu);
-
- put_cpu();
-}
-
-static void blk_trace_set_ht_offsets(void)
-{
-#if defined(CONFIG_SCHED_SMT)
- int cpu, i;
-
- /*
- * now make sure HT siblings have the same time offset
- */
- preempt_disable();
- for_each_online_cpu(cpu) {
- unsigned long long *cpu_off, *sibling_off;
-
- for_each_cpu_mask(i, cpu_sibling_map[cpu]) {
- if (i == cpu)
- continue;
-
- cpu_off = &per_cpu(blk_trace_cpu_offset, cpu);
- sibling_off = &per_cpu(blk_trace_cpu_offset, i);
- *sibling_off = *cpu_off;
- }
- }
- preempt_enable();
-#endif
-}
-
-static __init int blk_trace_init(void)
-{
- mutex_init(&blk_tree_mutex);
- on_each_cpu(blk_trace_check_cpu_time, NULL, 1, 1);
- blk_trace_set_ht_offsets();
-
- return 0;
-}
-
-module_init(blk_trace_init);
-