Hi all, this series adds multiqueue support to the virtio-scsi driver, based on Jason Wang's work on virtio-net. It uses a simple queue steering algorithm that expects one queue per CPU. LUNs in the same target always use the same queue (so that commands are not reordered); queue switching occurs when the request being queued is the only one for the target. Also based on Jason's patches, the virtqueue affinity is set so that each CPU is associated to one virtqueue. I tested the patches with fio, using up to 32 virtio-scsi disks backed by tmpfs on the host. These numbers are with 1 LUN per target. FIO configuration ----------------- [global] rw=read bsrange=4k-64k ioengine=libaio direct=1 iodepth=4 loops=20 overall bandwidth (MB/s) ------------------------ # of targets single-queue multi-queue, 4 VCPUs multi-queue, 8 VCPUs 1 540 626 599 2 795 965 925 4 997 1376 1500 8 1136 2130 2060 16 1440 2269 2474 24 1408 2179 2436 32 1515 1978 2319 (These numbers for single-queue are with 4 VCPUs, but the impact of adding more VCPUs is very limited). avg bandwidth per LUN (MB/s) ---------------------------- # of targets single-queue multi-queue, 4 VCPUs multi-queue, 8 VCPUs 1 540 626 599 2 397 482 462 4 249 344 375 8 142 266 257 16 90 141 154 24 58 90 101 32 47 61 72 Patch 1 adds a new API to add functions for piecewise addition for buffers, which enables various simplifications in virtio-scsi (patches 2-3) and a small performance improvement of 2-6%. Patches 4 and 5 add multiqueuing. I'm mostly looking for comments on the new API of patch 1 for inclusion into the 3.9 kernel. Thanks to Wao Ganlong for help rebasing and benchmarking these patches. Paolo Bonzini (5): virtio: add functions for piecewise addition of buffers virtio-scsi: use functions for piecewise composition of buffers virtio-scsi: redo allocation of target data virtio-scsi: pass struct virtio_scsi to virtqueue completion function virtio-scsi: introduce multiqueue support drivers/scsi/virtio_scsi.c | 374 +++++++++++++++++++++++++++++------------- drivers/virtio/virtio_ring.c | 205 ++++++++++++++++++++++++ include/linux/virtio.h | 21 +++ 3 files changed, 485 insertions(+), 115 deletions(-) -- 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
