timers: split process wide cpu clocks/timers
Change the process wide cpu timers/clocks so that we:
1) don't mess up the kernel with too many threads,
2) don't have a per-cpu allocation for each process,
3) have no impact when not used.
In order to accomplish this we're going to split it into two parts:
- clocks; which can take all the time they want since they run
from user context -- ie. sys_clock_gettime(CLOCK_PROCESS_CPUTIME_ID)
- timers; which need constant time sampling but since they're
explicity used, the user can pay the overhead.
The clock readout will go back to a full sum of the thread group, while the
timers will run of a global 'clock' that only runs when needed, so only
programs that make use of the facility pay the price.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Reviewed-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 2e0646a..082d761 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -443,7 +443,6 @@
* @utime: time spent in user mode, in &cputime_t units
* @stime: time spent in kernel mode, in &cputime_t units
* @sum_exec_runtime: total time spent on the CPU, in nanoseconds
- * @lock: lock for fields in this struct
*
* This structure groups together three kinds of CPU time that are
* tracked for threads and thread groups. Most things considering
@@ -454,23 +453,33 @@
cputime_t utime;
cputime_t stime;
unsigned long long sum_exec_runtime;
- spinlock_t lock;
};
/* Alternate field names when used to cache expirations. */
#define prof_exp stime
#define virt_exp utime
#define sched_exp sum_exec_runtime
+#define INIT_CPUTIME \
+ (struct task_cputime) { \
+ .utime = cputime_zero, \
+ .stime = cputime_zero, \
+ .sum_exec_runtime = 0, \
+ }
+
/**
- * struct thread_group_cputime - thread group interval timer counts
- * @totals: thread group interval timers; substructure for
- * uniprocessor kernel, per-cpu for SMP kernel.
+ * struct thread_group_cputimer - thread group interval timer counts
+ * @cputime: thread group interval timers.
+ * @running: non-zero when there are timers running and
+ * @cputime receives updates.
+ * @lock: lock for fields in this struct.
*
* This structure contains the version of task_cputime, above, that is
- * used for thread group CPU clock calculations.
+ * used for thread group CPU timer calculations.
*/
-struct thread_group_cputime {
- struct task_cputime totals;
+struct thread_group_cputimer {
+ struct task_cputime cputime;
+ int running;
+ spinlock_t lock;
};
/*
@@ -519,10 +528,10 @@
cputime_t it_prof_incr, it_virt_incr;
/*
- * Thread group totals for process CPU clocks.
- * See thread_group_cputime(), et al, for details.
+ * Thread group totals for process CPU timers.
+ * See thread_group_cputimer(), et al, for details.
*/
- struct thread_group_cputime cputime;
+ struct thread_group_cputimer cputimer;
/* Earliest-expiration cache. */
struct task_cputime cputime_expires;
@@ -2191,27 +2200,26 @@
/*
* Thread group CPU time accounting.
*/
+void thread_group_cputime(struct task_struct *tsk, struct task_cputime *times);
static inline
-void thread_group_cputime(struct task_struct *tsk, struct task_cputime *times)
+void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times)
{
- struct task_cputime *totals = &tsk->signal->cputime.totals;
+ struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
unsigned long flags;
- spin_lock_irqsave(&totals->lock, flags);
- *times = *totals;
- spin_unlock_irqrestore(&totals->lock, flags);
+ WARN_ON(!cputimer->running);
+
+ spin_lock_irqsave(&cputimer->lock, flags);
+ *times = cputimer->cputime;
+ spin_unlock_irqrestore(&cputimer->lock, flags);
}
static inline void thread_group_cputime_init(struct signal_struct *sig)
{
- sig->cputime.totals = (struct task_cputime){
- .utime = cputime_zero,
- .stime = cputime_zero,
- .sum_exec_runtime = 0,
- };
-
- spin_lock_init(&sig->cputime.totals.lock);
+ sig->cputimer.cputime = INIT_CPUTIME;
+ spin_lock_init(&sig->cputimer.lock);
+ sig->cputimer.running = 0;
}
static inline void thread_group_cputime_free(struct signal_struct *sig)