I'm using FreeBSD on KVM virtual machine from a hosting provider. On both 11.1-RELEASE and 12.0-CURRENT (2018-01-18) reading /dev/vtbd0 device hangs. Using CentOS 6.9 I'm able to read full /dev/vda device without a hang. - Command # dd if=/dev/vtbd0 of=/dev/null bs=1M will eventually hang. - top shows dd in physrd state. - gstat shows L(q) equal to 1 or 2 (depending on a try), all the IOPS and throughput indications are zero for /dev/vtbd0 - dd can't be terminated with SIGKILL - the only way to terminate the dd process is # devctl disable vtbd0 Server configuration: RAM: 512MB CPU: 1x Intel Xeon E5-2620 v3 @ 2.40 GHz Disk: 250GB virtio-blk <Additional info will be attached in a separate files> The info from the hosting provider: We are running the latest QEMU version and the latest 3.1 branch kernel, which was released for fixing the Spectre and Meltdown vulnerabilities. I'm still paying for the server, but I want to leave it in this state for now to help investigate the issue.
Created attachment 190131 [details] `sysctl -a` output Collected running 12.0-CURRENT live CD
Created attachment 190132 [details] `ps -lux` output Collected running 12.0-CURRENT live CD
Created attachment 190133 [details] `pciconf -lvc` output Collected running 12.0-CURRENT live CD
Created attachment 190134 [details] `kenv` output Collected running 12.0-CURRENT live CD
Created attachment 190135 [details] `gstat` output Collected running 12.0-CURRENT live CD
Can you please include the output of "procstat -k"? Thanks.
Created attachment 190173 [details] `procstat -ak` output Collected running 12.0-CURRENT live CD
`procstat -ak` output was collected in the hanged state. `dd` process in the one reading the virtio-blk device.
^Triage: correct assignment. Discussed with: koobs@.
^Triage: I'm sorry that this PR did not get addressed in a timely fashion. By now, the version that it was created against is long out of support. Please re-open if it is still a problem on a supported version.