Re: [PATCH] [APIC] Optimize searching for highest IRR

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Gleb Natapov wrote:
Most of the time IRR is empty, so instead of scanning the whole IRR on
each VM entry keep a variable that tells us if IRR is not empty. IRR
will have to be scanned twice on each IRQ delivery, but this is much more
rare than VM entry.

static inline int apic_find_highest_irr(struct kvm_lapic *apic)
 {
 	int result;
- result = find_highest_vector(apic->regs + APIC_IRR);
+	if (!apic->irr_pending)
+		return -1;

smp_mb__before_clear_bit(), to prevent the cpu speculating the IRR.

+
+	result = apic_search_irr(apic);
 	ASSERT(result == -1 || result >= 16);
return result;
 }
+static inline void apic_clear_irr(int vec, struct kvm_lapic *apic)
+{
+	apic->irr_pending = false;
+	apic_clear_vector(vec, apic->regs + APIC_IRR);

smp_rmb()

+	if (apic_search_irr(apic) != -1)
+		apic->irr_pending = true;



--
error compiling committee.c: too many arguments to function

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