Vivek Goyal <vgoyal@xxxxxxxxxx> writes: > Are you using CFQ in the host? What is the host kernel version? I am not sure > what is the problem here but you might want to play with IO controller and put > these guests in individual cgroups and see if you get better throughput even > with cache=writethrough. Hi. We're using the deadline IO scheduler on 2.6.32.7. We got better performance from deadline than from cfq when we last tested, which was admittedly around the 2.6.30 timescale so is now a rather outdated measurement. > If the problem is that if sync writes from different guests get intermixed > resulting in more seeks, IO controller might help as these writes will now > go on different group service trees and in CFQ, we try to service requests > from one service tree at a time for a period before we switch the service > tree. Thanks for the suggestion: I'll have a play with this. I currently use /sys/kernel/uids/N/cpu_share with one UID per guest to divide up the CPU between guests, but this could just as easily be done with a cgroup per guest if a side-effect is to provide a hint about IO independence to CFQ. Best wishes, Chris. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
