On 04/04/2012 11:38 AM, Michael S. Tsirkin wrote: > > > > > > > > A performance note: delivering an interrupt needs to search all vcpus > > > for an APIC ID match. The previous plan was to cache (or pre-calculate) > > > this lookup in the irq routing table. Now it looks like we'll need a > > > separate cache for this. > > > > As this is non-existent until today, we don't regress here. And it can > > still be added on top later on, transparently. > > I always worry about hash collisions and the cost of > calculating good hash functions. > > We could instead return an index in the cache on injection, maintain in > userspace and use it for fast path on the next injection. Ahem, that is almost the existing routing table to a T. > Will make it easy to use an array index instead of a hash here, > and fallback to a slower ID lookup on mismatch. Need a free ioctl so we can reuse IDs. > Until we do have this fast path we can just fill this value with zeros, > so kernel patch (almost) does not need to change for this - > just the header. Partially implemented interfaces invite breakage. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
