On 03/02/2015 03:31, Wangting (Kathy) wrote: > Hi Paolo, > > Recently I test IO performance with virtio-scsi, and find out that the patch > of > "virtio-scsi: add support for the any_layout feature" affects IO performance > of model > with 4KB 32iodepth sequence read. > > Why cdb and sense is removed from the struct of VirtIOSCSICmdReq and > VirtIOSCSICmdResp?
Because I could not find any other way to implement ANY_LAYOUT, and virtio 1.0 requires that feature. The performance however was already improved in commit faf1e1f (virtio-scsi: Optimize virtio_scsi_init_req, 2014-09-16). Paolo > How do you consider the impact of the changes to the performance? > Although the latest version of qemu can optimize the performance by the way > of reading merger, > I think the affect of this patch cannot be ignored.
