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Commit 8f4d37ec authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
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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: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 02b67cc3

arch/x86/kernel/entry_64.S

+3 −3
Original line number Diff line number Diff line
@@ -283,7 +283,7 @@ sysret_careful: 
sysret_signal:

	TRACE_IRQS_ON

	sti

	testl $(_TIF_SIGPENDING|_TIF_SINGLESTEP|_TIF_MCE_NOTIFY),%edx

	testl $_TIF_DO_NOTIFY_MASK,%edx

	jz    1f



	/* Really a signal */
@@ -377,7 +377,7 @@ int_very_careful: 
	jmp int_restore_rest

	

int_signal:

	testl $(_TIF_SIGPENDING|_TIF_SINGLESTEP|_TIF_MCE_NOTIFY),%edx

	testl $_TIF_DO_NOTIFY_MASK,%edx

	jz 1f

	movq %rsp,%rdi		# &ptregs -> arg1

	xorl %esi,%esi		# oldset -> arg2
@@ -603,7 +603,7 @@ retint_careful: 
	jmp retint_check

	

retint_signal:

	testl $(_TIF_SIGPENDING|_TIF_SINGLESTEP|_TIF_MCE_NOTIFY),%edx

	testl $_TIF_DO_NOTIFY_MASK,%edx

	jz    retint_swapgs

	TRACE_IRQS_ON

	sti

arch/x86/kernel/signal_32.c

+3 −0
Original line number Diff line number Diff line
@@ -659,5 +659,8 @@ void do_notify_resume(struct pt_regs *regs, void *_unused, 
	if (thread_info_flags & (_TIF_SIGPENDING | _TIF_RESTORE_SIGMASK))

		do_signal(regs);



	if (thread_info_flags & _TIF_HRTICK_RESCHED)

		hrtick_resched();

	

	clear_thread_flag(TIF_IRET);

}

arch/x86/kernel/signal_64.c

+3 −0
Original line number Diff line number Diff line
@@ -480,6 +480,9 @@ do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags) 
	/* deal with pending signal delivery */

	if (thread_info_flags & (_TIF_SIGPENDING|_TIF_RESTORE_SIGMASK))

		do_signal(regs);



	if (thread_info_flags & _TIF_HRTICK_RESCHED)

		hrtick_resched();

}



void signal_fault(struct pt_regs *regs, void __user *frame, char *where)

include/asm-x86/thread_info_32.h

+2 −0
Original line number Diff line number Diff line
@@ -132,6 +132,7 @@ static inline struct thread_info *current_thread_info(void) 
#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 @@ static inline struct thread_info *current_thread_info(void) 
#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)

include/asm-x86/thread_info_64.h

+5 −0
Original line number Diff line number Diff line
@@ -115,6 +115,7 @@ static inline struct thread_info *stack_thread_info(void) 
#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 @@ static inline struct thread_info *stack_thread_info(void) 
#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 @@ static inline struct thread_info *stack_thread_info(void) 
/* 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)