Re: assign-dev: Purpose of interrupt_work

[Jan Kiszka <jan.kiszka@web.de>]

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Gleb Natapov wrote:
> On Mon, Oct 12, 2009 at 10:16:56AM +0200, Jan Kiszka wrote:
>>>>> Apic is lockless. For ioapic/pic I used spinlocks initially, but Avi
>>>>> prefers mutexes. Theoretically it is possible to make them lockless,
>>>>> but code will be complex and eventually more slow, since more then two
>>>>> atomic operation will be used on irq injection path.
>>>> Well, lockless is another thing.
>>>>
>>>> But also converting to spinlocks would indeed add some overhead:
>>>> irqsave/restore. But I wonder if this isn't worth it, at least when
>>>> looking at the (supposed to be fast) device passthrough scenario which
>>>> would be simpler and faster.
>>>>
>>> Avi's point in favor of mutex is: they are as fast as spinlocks when
>>> congested and allows preemption when held.
>> ...but require scheduler activity in case of dev-passthrough, which is
>> surely playing in a different league.
>>
> I'd rather remove dev-passthrough completely than continue adding hack upon hack
> upon hack to make is some times kinda sorta work :)

Hmm, is this code not needed for the VT-d & Co. case? Or what is the
alternative?

Jan


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