sched: high-res preemption tick
Use HR-timers (when available) to deliver an accurate preemption tick.
The regular scheduler tick that runs at 1/HZ can be too coarse when nice
level are used. The fairness system will still keep the cpu utilisation 'fair'
by then delaying the task that got an excessive amount of CPU time but try to
minimize this by delivering preemption points spot-on.
The average frequency of this extra interrupt is sched_latency / nr_latency.
Which need not be higher than 1/HZ, its just that the distribution within the
sched_latency period is important.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/asm-x86/thread_info_32.h b/include/asm-x86/thread_info_32.h
index 22a8cbc..ef58fd2 100644
--- a/include/asm-x86/thread_info_32.h
+++ b/include/asm-x86/thread_info_32.h
@@ -132,6 +132,7 @@
#define TIF_SYSCALL_AUDIT 6 /* syscall auditing active */
#define TIF_SECCOMP 7 /* secure computing */
#define TIF_RESTORE_SIGMASK 8 /* restore signal mask in do_signal() */
+#define TIF_HRTICK_RESCHED 9 /* reprogram hrtick timer */
#define TIF_MEMDIE 16
#define TIF_DEBUG 17 /* uses debug registers */
#define TIF_IO_BITMAP 18 /* uses I/O bitmap */
@@ -147,6 +148,7 @@
#define _TIF_SYSCALL_AUDIT (1<<TIF_SYSCALL_AUDIT)
#define _TIF_SECCOMP (1<<TIF_SECCOMP)
#define _TIF_RESTORE_SIGMASK (1<<TIF_RESTORE_SIGMASK)
+#define _TIF_HRTICK_RESCHED (1<<TIF_HRTICK_RESCHED)
#define _TIF_DEBUG (1<<TIF_DEBUG)
#define _TIF_IO_BITMAP (1<<TIF_IO_BITMAP)
#define _TIF_FREEZE (1<<TIF_FREEZE)
diff --git a/include/asm-x86/thread_info_64.h b/include/asm-x86/thread_info_64.h
index beae2bf..7f6ee68 100644
--- a/include/asm-x86/thread_info_64.h
+++ b/include/asm-x86/thread_info_64.h
@@ -115,6 +115,7 @@
#define TIF_SECCOMP 8 /* secure computing */
#define TIF_RESTORE_SIGMASK 9 /* restore signal mask in do_signal */
#define TIF_MCE_NOTIFY 10 /* notify userspace of an MCE */
+#define TIF_HRTICK_RESCHED 11 /* reprogram hrtick timer */
/* 16 free */
#define TIF_IA32 17 /* 32bit process */
#define TIF_FORK 18 /* ret_from_fork */
@@ -133,6 +134,7 @@
#define _TIF_SECCOMP (1<<TIF_SECCOMP)
#define _TIF_RESTORE_SIGMASK (1<<TIF_RESTORE_SIGMASK)
#define _TIF_MCE_NOTIFY (1<<TIF_MCE_NOTIFY)
+#define _TIF_HRTICK_RESCHED (1<<TIF_HRTICK_RESCHED)
#define _TIF_IA32 (1<<TIF_IA32)
#define _TIF_FORK (1<<TIF_FORK)
#define _TIF_ABI_PENDING (1<<TIF_ABI_PENDING)
@@ -146,6 +148,9 @@
/* work to do on any return to user space */
#define _TIF_ALLWORK_MASK (0x0000FFFF & ~_TIF_SECCOMP)
+#define _TIF_DO_NOTIFY_MASK \
+ (_TIF_SIGPENDING|_TIF_SINGLESTEP|_TIF_MCE_NOTIFY|_TIF_HRTICK_RESCHED)
+
/* flags to check in __switch_to() */
#define _TIF_WORK_CTXSW (_TIF_DEBUG|_TIF_IO_BITMAP)
diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index 7a9398e..ecc8e26 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -217,6 +217,11 @@
return timer->base->get_time();
}
+static inline int hrtimer_is_hres_active(struct hrtimer *timer)
+{
+ return timer->base->cpu_base->hres_active;
+}
+
/*
* The resolution of the clocks. The resolution value is returned in
* the clock_getres() system call to give application programmers an
@@ -248,6 +253,10 @@
return timer->base->softirq_time;
}
+static inline int hrtimer_is_hres_active(struct hrtimer *timer)
+{
+ return 0;
+}
#endif
extern ktime_t ktime_get(void);
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 7907845..43e0339 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -257,6 +257,7 @@
extern void account_process_tick(struct task_struct *task, int user);
extern void update_process_times(int user);
extern void scheduler_tick(void);
+extern void hrtick_resched(void);
extern void sched_show_task(struct task_struct *p);
@@ -849,7 +850,7 @@
#endif
void (*set_curr_task) (struct rq *rq);
- void (*task_tick) (struct rq *rq, struct task_struct *p);
+ void (*task_tick) (struct rq *rq, struct task_struct *p, int queued);
void (*task_new) (struct rq *rq, struct task_struct *p);
void (*set_cpus_allowed)(struct task_struct *p, cpumask_t *newmask);