VIRTIO SCSI vs VIRTIO SCSI single

mir

Famous Member
Apr 14, 2012
3,559
120
83
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
 

spirit

Famous Member
Apr 2, 2010
5,782
676
133
www.odiso.com
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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