On 13/02/2015 02:21, Fam Zheng wrote: >> Could you just do set_aio_context for all devices when starting >> dataplane? For example with a new scsi_device_set_aio_context function >> (and a new method in SCSIDeviceClass). >> >> Maybe I'm missing the obvious. :) > > Per VQ IOThread stills needs it, in the case that guest switches the VQ of a > disk on the fly.
Per VQ iothread is far away though. Multiqueue aims at parallelizing accesses *to the same disk from different CPUs*, not at parallelizing accesses to different disks. As long as bdrv_set_aio_context does bdrv_drain_all, something has to change for multiqueue dataplane: either stop using bdrv_set_aio_context, or stop doing bdrv_drain_all. In either case, the changes are large enough that we shouldn't code for a case that doesn't exist yet. In addition, making the code more similar for virtio-blk and virtio-scsi dataplane is good, because the same changes can apply to both in the future. Paolo
