Hi, this is a fairly grave bug for me. I imagine it's specific to my setup, otherwise more people would complain. KVM or open-iscsi, or both involved. Posting bug report here.
The setup is: Dual socket Host with 2x Intel Xeon L5520 2x Ethernet controller: Intel Corporation 82576 Gigabit Network Connection (rev 01) Debian Squeeze / Unstable mix on Host and Guest Kernel 3.2 on Host and Guest Qemu-KVM 1.0 (current Debian package = 1.01) (the bug was encountered with earlier kernel / qemu versions on same hardware) Guest with -smp 2 or higher and bridged networking (br0, tap, etc.) Logical block size for target is 4096 bytes. Another target uses 512 bytes, same problem. After --login, target is represented as /dev/sdc. # cat /dev/sdc > /dev/null; dstat shows a bit of traffic, then silence, 100% wait on 1 vcpu. Occasionally, data flows. Failed workarounds: - disabling all offloading functions of guest and host ethernet NIC - changing -cpu to kvm64 - changing virtual network card from virtio-net to e1000, rtl8139 - without vhost_net module - forcing host NIC to 100 MBit/s - tweaking coalesce, ring buffer size of host NIC "Working" workarounds: - queue_depth. default 32, reducing to 1 prevents bug, 2 and higher triggers bug - read_ahead_kb. default is 128, reducing to 64 prevents bug, 65 and higher triggers bug. - reducing guest cpu count to 1. - using host instead of guest for iscsi yields ~70 MiB/s throughput. Oddities: - limiting rate does not prevent bug: # echo 1 > /proc/sys/vm/drop_caches; pv -L1000k /dev/sdc > /dev/null - writing data does not trigger bug: # cat /dev/zero > /dev/sdc - reading while writing, triggering bug, will cause both to interrupt - booting VM without hardware assisted virtualization, things got worse. even queue_depth = 1 and read_ahead_kb = 64 did not help. Any ideas? Greetings, Pierre Beck -- You received this message because you are subscribed to the Google Groups "open-iscsi" group. To view this discussion on the web visit https://groups.google.com/d/msg/open-iscsi/-/IfrGLewwnLQJ. To post to this group, send email to open-iscsi@googlegroups.com. To unsubscribe from this group, send email to open-iscsi+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/open-iscsi?hl=en.
