performance counters: core code

Implement the core kernel bits of Performance Counters subsystem.

The Linux Performance Counter subsystem provides an abstraction of
performance counter hardware capabilities. It provides per task and per
CPU counters, and it provides event capabilities on top of those.

Performance counters are accessed via special file descriptors.
There's one file descriptor per virtual counter used.

The special file descriptor is opened via the perf_counter_open()
system call:

 int
 perf_counter_open(u32 hw_event_type,
                   u32 hw_event_period,
                   u32 record_type,
                   pid_t pid,
                   int cpu);

The syscall returns the new fd. The fd can be used via the normal
VFS system calls: read() can be used to read the counter, fcntl()
can be used to set the blocking mode, etc.

Multiple counters can be kept open at a time, and the counters
can be poll()ed.

See more details in Documentation/perf-counters.txt.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 24 insertions, 0 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index b7480fb5c3dc..254d56de2548 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2212,6 +2212,27 @@ static int sched_balance_self(int cpu, int flag)
 
 #endif /* CONFIG_SMP */
 
+/**
+ * task_oncpu_function_call - call a function on the cpu on which a task runs
+ * @p:          the task to evaluate
+ * @func:       the function to be called
+ * @info:       the function call argument
+ *
+ * Calls the function @func when the task is currently running. This might
+ * be on the current CPU, which just calls the function directly
+ */
+void task_oncpu_function_call(struct task_struct *p,
+                              void (*func) (void *info), void *info)
+{
+        int cpu;
+
+        preempt_disable();
+        cpu = task_cpu(p);
+        if (task_curr(p))
+                smp_call_function_single(cpu, func, info, 1);
+        preempt_enable();
+}
+
 /***
  * try_to_wake_up - wake up a thread
  * @p: the to-be-woken-up thread
@@ -2534,6 +2555,7 @@ prepare_task_switch(struct rq *rq, struct task_struct *prev,
                     struct task_struct *next)
 {
         fire_sched_out_preempt_notifiers(prev, next);
+        perf_counter_task_sched_out(prev, cpu_of(rq));
         prepare_lock_switch(rq, next);
         prepare_arch_switch(next);
 }
@@ -2574,6 +2596,7 @@ static void finish_task_switch(struct rq *rq, struct task_struct *prev)
          */
         prev_state = prev->state;
         finish_arch_switch(prev);
+        perf_counter_task_sched_in(current, cpu_of(rq));
         finish_lock_switch(rq, prev);
 #ifdef CONFIG_SMP
         if (current->sched_class->post_schedule)
@@ -4296,6 +4319,7 @@ void scheduler_tick(void)
         rq->idle_at_tick = idle_cpu(cpu);
         trigger_load_balance(rq, cpu);
 #endif
+        perf_counter_task_tick(curr, cpu);
 }
 
 #if defined(CONFIG_PREEMPT) && (defined(CONFIG_DEBUG_PREEMPT) || \