Il 17/07/2012 11:45, Michael S. Tsirkin ha scritto: >> So it begs the question, is it going to be used in production, or just a >> useful reference tool? > > Sticking to raw already makes virtio-blk faster, doesn't it? > In that vhost-blk looks to me like just another optimization option. > Ideally I think user just should not care where do we handle virtio: > in-kernel or in userspace. One can imagine it being enabled/disabled > automatically if none of the features unsupported by it are used. Ok, that would make more sense. One difference between vhost-blk and vhost-net is that for vhost-blk there are also management actions that would trigger the switch, for example a live snapshot. So a prerequisite for vhost-blk would be that it is possible to disable it on the fly while the VM is running, as soon as all in-flight I/O is completed. (Note that, however, this is not possible for vhost-scsi, because it really exposes different hardware to the guest. It must not happen that a kernel upgrade or downgrade toggles between userspace SCSI and vhost-scsi, for example). >> having to >> support the API; having to handle transition from one more thing when >> something better comes out. > > Well this is true for any code. If the limited featureset which > vhost-blk can accelerate is something many people use, then accelerating > by 5-15% might outweight support costs. It is definitely what people use if they are interested in performance. Paolo -- 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
