Commit e7ab0f7b authored Oct 09, 2009 by Ingo Molnar

Revert "x86, timers: Check for pending timers after (device) interrupts"



This reverts commit 9bcbdd9c.

The real bug producing LatencyTop latencies has been fixed in:

  f5dc3753: sched: Update the clock of runqueue select_task_rq() selected

And the commit being reverted here triggers local timer processing
from every device IRQ. If device IRQs come in at a high frequency,
this could cause a performance regression.

The commit being reverted here purely 'fixed' the reported latency
as a side effect, because CPUs were being moved out of idle more
often.

Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Frans Pop <elendil@planet.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
LKML-Reference: <20091008064041.67219b13@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent f5dc3753

arch/x86/kernel/irq.c

+0 −2

Original line number	Diff line number	Diff line
		@@ -244,7 +244,6 @@ unsigned int __irq_entry do_IRQ(struct pt_regs *regs)
		__func__, smp_processor_id(), vector, irq);
		}

		run_local_timers();
		irq_exit();

		set_irq_regs(old_regs);
		@@ -269,7 +268,6 @@ void smp_generic_interrupt(struct pt_regs *regs)
		if (generic_interrupt_extension)
		generic_interrupt_extension();

		run_local_timers();
		irq_exit();

		set_irq_regs(old_regs);

arch/x86/kernel/smp.c

+0 −1

Original line number	Diff line number	Diff line
		@@ -198,7 +198,6 @@ void smp_reschedule_interrupt(struct pt_regs *regs)
		{
		ack_APIC_irq();
		inc_irq_stat(irq_resched_count);
		run_local_timers();
		/*
		* KVM uses this interrupt to force a cpu out of guest mode
		*/

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