Re: [RFC PATCH 0/2] irq destination caching prototype

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On 08/13/2012 01:24 PM, Gleb Natapov wrote:
> On Mon, Aug 13, 2012 at 01:21:33PM +0300, Avi Kivity wrote:
>> On 08/13/2012 01:16 PM, Gleb Natapov wrote:
>> > On Mon, Aug 13, 2012 at 01:12:46PM +0300, Michael S. Tsirkin wrote:
>> >> On Mon, Aug 13, 2012 at 12:36:41PM +0300, Avi Kivity wrote:
>> >> > On 08/13/2012 12:16 PM, Gleb Natapov wrote:
>> >> > > Here is a quick prototype of what we discussed yesterday. This one
>> >> > > caches only MSI interrupts for now. The obvious problem is that not
>> >> > > all interrupts (namely IPIs and MSIs using KVM_CAP_SIGNAL_MSI) use irq
>> >> > > routing table, so they cannot be cached.
>> >> > 
>> >> > We can have a small rcu-managed hash table to look those up.
>> >> 
>> >> Yes but how small? We probably need at least one entry
>> >> per vcpu, no?
>> >> 
>> > One entry? We will spend more time managing it than injecting interrupts
>> > :) ideally we need entry for each IPI sent and for each potential MSI
>> > from userspace. What happens when hash table is full? 
>> 
>> Drop the entire cache.
>> 
> OK. Then it should be big enough to not do it frequently.

Should be sized N * vcpus, where N is several dozen (generous amount of
non-device vectors, though multicast will break it since it's
essentially random).



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