Messages in this thread | | | Date | Tue, 22 Apr 2008 12:03:04 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: [PATCH 2/11] x86: convert to generic helpers for IPI function calls |
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[ Ingo added to cc, since this is x86-specific ]
On Tue, 22 Apr 2008, Jens Axboe wrote: > +++ b/arch/x86/kernel/apic_32.c > @@ -1357,6 +1357,10 @@ void __init smp_intr_init(void) > > /* IPI for generic function call */ > set_intr_gate(CALL_FUNCTION_VECTOR, call_function_interrupt); > + > + /* IPI for single call function */ > + set_intr_gate(CALL_FUNCTION_SINGLE_VECTOR, > + call_function_single_interrupt);
Ok, one more comment..
Why bother with separate vectors for this?
Why not just make the single vector do
void smp_call_function_interrupt(void) { ack_APIC_irq(); irq_enter(); generic_smp_call_function_single_interrupt(); generic_smp_call_function_interrupt(); #ifdef CONFIG_X86_32 __get_cpu_var(irq_stat).irq_call_count++; #else add_pda(irq_call_count, 1); #endif irq_exit(); }
since they are both doing the exact same thing anyway?
Do we really require us to be able to handle the "single" case _while_ a "multiple" case is busy? Aren't we running all of these things with interrupts disabled anyway, so that it cannot happen?
Or is it just a performance optimization? Do we expect to really have so many of the multiple interrupts that it's expensive to walk the list just because we also had a single interrupt to another CPU? That sounds a bit unlikely, but if true, very interesting..
Inquiring minds want to know..
Linus
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