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sched: high-res preemption tick

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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>
This commit is contained in:
Peter Zijlstra
2008-01-25 21:08:29 +01:00
committed by Ingo Molnar
parent 02b67cc3ba
commit 8f4d37ec07
12 changed files with 295 additions and 21 deletions
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arch/x86/kernel/entry_64.S
+3 -3
View File
@@ -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
View File
@@ -658,6 +658,9 @@ void do_notify_resume(struct pt_regs *regs, void *_unused,
/* 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();
clear_thread_flag(TIF_IRET);
}
arch/x86/kernel/signal_64.c
+3
View File
@@ -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)