On Mon, Jul 25, 2022 at 11:55:26PM +0300, Andrey Zhadchenko wrote: > Although QEMU virtio-blk is quite fast, there is still some room for > improvements. Disk latency can be reduced if we handle virito-blk requests > in host kernel so we avoid a lot of syscalls and context switches. > > The biggest disadvantage of this vhost-blk flavor is raw format. > Luckily Kirill Thai proposed device mapper driver for QCOW2 format to attach > files as block devices: https://www.spinics.net/lists/kernel/msg4292965.html
That one seems stalled. Do you plan to work on that too? > Also by using kernel modules we can bypass iothread limitation and finaly > scale > block requests with cpus for high-performance devices. This is planned to be > implemented in next version. > > Linux kernel module part: > https://lore.kernel.org/kvm/20220725202753.298725-1-andrey.zhadche...@virtuozzo.com/ > > test setups and results: > fio --direct=1 --rw=randread --bs=4k --ioengine=libaio --iodepth=128 > QEMU drive options: cache=none > filesystem: xfs > > SSD: > | randread, IOPS | randwrite, IOPS | > Host | 95.8k | 85.3k | > QEMU virtio | 57.5k | 79.4k | > QEMU vhost-blk | 95.6k | 84.3k | > > RAMDISK (vq == vcpu): > | randread, IOPS | randwrite, IOPS | > virtio, 1vcpu | 123k | 129k | > virtio, 2vcpu | 253k (??) | 250k (??) | > virtio, 4vcpu | 158k | 154k | > vhost-blk, 1vcpu | 110k | 113k | > vhost-blk, 2vcpu | 247k | 252k | > vhost-blk, 4vcpu | 576k | 567k | > > Andrey Zhadchenko (1): > block: add vhost-blk backend >From vhost/virtio side the patchset looks ok. But let's see what do block devs think about it. > configure | 13 ++ > hw/block/Kconfig | 5 + > hw/block/meson.build | 1 + > hw/block/vhost-blk.c | 395 ++++++++++++++++++++++++++++++++++ > hw/virtio/meson.build | 1 + > hw/virtio/vhost-blk-pci.c | 102 +++++++++ > include/hw/virtio/vhost-blk.h | 44 ++++ > linux-headers/linux/vhost.h | 3 + > 8 files changed, 564 insertions(+) > create mode 100644 hw/block/vhost-blk.c > create mode 100644 hw/virtio/vhost-blk-pci.c > create mode 100644 include/hw/virtio/vhost-blk.h > > -- > 2.31.1
