VIRTIO SCSI vs VIRTIO SCSI single

mir

Famous Member
Apr 14, 2012
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Copenhagen, Denmark
Can anybody explain the big performance difference between VIRTIO SCSI and VIRTIO SCSI single especially when using iotread=0 and iothread=1?

Code:
read : io=1637.7MB, bw=39596KB/s, iops=6491, runt= 42350msec  VIRTIO SCSI iotread=0
read : io=1637.7MB, bw=41136KB/s, iops=6744, runt= 40765msec  VIRTIO SCSI single iotread=0
read : io=1637.7MB, bw=36911KB/s, iops=6051, runt= 45431msec  VIRTIO SCSI iotread=1
read : io=1637.7MB, bw=53724KB/s, iops=8808, runt= 31213msec  VIRTIO SCSI single iotread=1

write: io=420263KB, bw=9923.6KB/s, iops=1625, runt= 42350msec VIRTIO SCSI iotread=0
write: io=420263KB, bw=10309KB/s, iops=1689, runt= 40765msec  VIRTIO SCSI single iotread=0
write: io=420263KB, bw=9250.6KB/s, iops=1515, runt= 45431msec VIRTIO SCSI iotread=1
write: io=420263KB, bw=13464KB/s, iops=2206, runt= 31213msec  VIRTIO SCSI single iotread=1
 
So iothread with virtio scsi is pointless or do I misunderstand you?
Yes pointless (at least un current qemu implémentation ) vitioscsi single has been added for iothread and multiqueues , which are both controller properties . (Same for virtioblk, which by default have akways 1 controller by disk)
 

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