On Mon, Sep 11, 2017 at 3:47 AM, Jason Wang <jasowang@xxxxxxxxxx> wrote: > > > On 2017年09月10日 13:06, Michael S. Tsirkin wrote: >> >> This is an update from v2 version. >> Changes: >> - update event suppression mechanism >> - add wrap counter: DESC_WRAP flag in addition to >> DESC_DRIVER flag used for validity so device does not have to >> write out all used descriptors. > > > Do we have benchmark result to show the advantage of DESC_DRIVER over e.g > avail/used index? The KVM forum presentation has some numbers. I'm not sure that synthetic benchmarks will provide much value, as we understand the trade-off quite well. The benefit of this model is improved best case performance, by having a single cacheline read instead of two for the indirect used/avail ring model. The drawback is worse worst case, as scanning the ring of descriptors introduces more cacheline misses than scanning the compressed used/avail ring. This model is easier to implement in hardware and the common case is likely close to the best case, so I think it makes sense. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
