This patchset allows the virtio-blk driver to support much higher IOP rates which can be driven out of modern PCI-e flash devices. At this point it really is just a RFC due to various issues. The first four patches are infrastructure that could go in fairly soon as far as I'm concerned. Patch 5 implements the actual ->make_request support and still has a few issues, see there for more details. With it I can driver my PCI-e test devices to 85-90% of the native IOPS and bandwith, but be warned that this is still a fairly low end setup as far as expensive flash storage is concerned. One big downside that is has is that it current exposes a nasty race in the qemu virtqueue code - just running xfstests inside a guest using the new virtio-blk driver (even on a slow device) will trigger it and lead to a filesystem shutdown. I've tracked it down to getting data I/O segments overwritten with status s/g list entries, but got lost at that point. I can start a separate thread on it. Besides that it is missing a few features, and we have to decided how to select which mode to use in virtio-blk - either a module option, sysfs attribute or something that the host communicates. Or maybe decide that just going with ->make_request alone is fine, even on my cheap laptop SSD it actually is just as fast if not slightly faster than the request based variant on my laptop. There are a few other bottlenecks in virtio that this exposes. The first one is the low queue length of just 128 entries in the virtio-blk queue - to drive higher IOPs with a deep queue we absolutely need to increment that. Comments welcome! -- 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
