[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Paravirtualised drivers for fully virtualised domains, rev9
> > > Here is what I have found so far in trying to chase down the cause of > the > > > slowdown. > > > The qemu-dm process is running 99.9% of the CPU on dom0. > > That seems very wrong. When I try this, the device model is almost > > completely idle. Could you see what strace says, please, or if there > > are any strange messages in the /var/log/qemu-dm. file? > Looks like I jumped the gun in relating the 99.9% CPU usage for qemu-dm and > the network. I start up the HVM domain and without running any tests > qemu-dm is chewing up 99.9% of the CPU in dom0. So it appears that the > 100% CPU qemu usage is a problem by itself. Looks like the same problem > Harry Butterworth is seeing. qemu-dm misbehaving could certainly lead to the netif going very slowly. > > 2) How often is the event channel interrupt firing according to > > /proc/interrupts? I see about 50k-150k/second. > I'm seeing ~ 500/s when netpipe-tcp reports decent throughput at smaller > buffer sizes and then ~50/s when the throughput drops at larger buffer > sizes. How large do they have to be to cause problems? > > The other thing is that these drivers seem to be very sensitive to > > kernel debugging options in the domU. If you've got anything enabled > > in the kernel hacking menu it might be worth trying again with that > > switched off. > Kernel debugging is on. I also have Oprofile enabled. I'll build a kernel > without those and see if it helps. Worth a shot. It shouldn't cause the problems with qemu, though. > > > It appears there is some interaction between using the xen-vnif > > > driver and the qemu timer code. I'm still exploring. > > I'd be happier if I could reproduce this problem here. Are you > > running SMP? PAE? 64 bit? What kernel are you running in the domU? > UP kernels in both the domU and dom0 (although the scheduler likes to move > the 1 vcpu in dom0 around to different physical CPUs). 64-bit kernels on > both. I've mostly been testing with 32 bit PAE. I'll have a go with a 64 bit system on Monday. Thanks, Steven. Attachment:
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