On Mon, Sep 18, 2023 at 12:16:02PM -0400, Stefan Hajnoczi wrote: > virtio-blk and virtio-scsi devices need a way to specify the mapping between > IOThreads and virtqueues. At the moment all virtqueues are assigned to a > single > IOThread or the main loop. This single thread can be a CPU bottleneck, so it > is > necessary to allow finer-grained assignment to spread the load. With this > series applied, "pidstat -t 1" shows that guests with -smp 2 or higher are > able > to exploit multiple IOThreads. > > This series introduces command-line syntax for the new iothread-vq-mapping > property is as follows: > > --device > '{"driver":"virtio-blk-pci","iothread-vq-mapping":[{"iothread":"iothread0","vqs":[0,1,2]},...]},...' > > IOThreads are specified by name and virtqueues are specified by 0-based > index. > > It will be common to simply assign virtqueues round-robin across a set > of IOThreads. A convenient syntax that does not require specifying > individual virtqueue indices is available: > > --device > '{"driver":"virtio-blk-pci","iothread-vq-mapping":[{"iothread":"iothread0"},{"iothread":"iothread1"},...]},...' > > There is no way to reassign virtqueues at runtime and I expect that to be a > very rare requirement. > > Note that JSON --device syntax is required for the iothread-vq-mapping > parameter because it's non-scalar. > > Based-on: 20230912231037.826804-1-stefa...@redhat.com ("[PATCH v3 0/5] > block-backend: process I/O in the current AioContext")
Acked-by: Michael S. Tsirkin <m...@redhat.com> More of a block thingy so pls use that tree. > Stefan Hajnoczi (2): > qdev: add IOThreadVirtQueueMappingList property type > virtio-blk: add iothread-vq-mapping parameter > > qapi/virtio.json | 30 +++++ > hw/block/dataplane/virtio-blk.h | 3 + > include/hw/qdev-properties-system.h | 4 + > include/hw/virtio/virtio-blk.h | 2 + > hw/block/dataplane/virtio-blk.c | 163 +++++++++++++++++++++------- > hw/block/virtio-blk.c | 92 ++++++++++++++-- > hw/core/qdev-properties-system.c | 47 ++++++++ > 7 files changed, 287 insertions(+), 54 deletions(-) > > -- > 2.41.0