On 09/30/2012 01:23 PM, Fengguang Wu wrote: > On Sun, Sep 30, 2012 at 01:10:55PM +0200, Avi Kivity wrote: >> On 09/28/2012 05:35 AM, Paul E. McKenney wrote: >> > On Thu, Sep 27, 2012 at 12:40:44PM +0800, Fengguang Wu wrote: >> >> On Wed, Sep 26, 2012 at 09:28:50PM -0700, Paul E. McKenney wrote: >> >> > On Thu, Sep 27, 2012 at 10:54:00AM +0800, Fengguang Wu wrote: >> >> > > On Wed, Sep 26, 2012 at 09:45:43AM -0700, Paul E. McKenney wrote: >> >> > > > On Wed, Sep 26, 2012 at 04:15:01PM +0800, Fengguang Wu wrote: >> > >> > [ . . . ] >> > >> >> > > > But could you also please send your .config file and a description of >> >> > > >> >> > > .config attached. >> >> > > >> >> > > > the workload you are running? >> >> > > >> >> > > It's basically the below commands. The exact initrd is not relevant in >> >> > > this case because it's a boot time warning before user space is >> >> > > started. The stalls roughly happen 1 time on every 10 boots. >> >> > >> >> > Yow!!! >> >> > >> >> > You have severe cross-CPU time-synchronization problems. See for >> >> > example the first dmesg, with the relevant part extracted right here. >> >> > One CPU believes that it is about 37 seconds past boot, and the other >> >> > CPU beleives that it is about 137 seconds past boot. Given that large >> >> > of a time difference, an RCU CPU stall warning is expected behavior. >> >> >> >> Good spot! Yeah I noticed that huge timestamp gap, however didn't take >> >> it seriously enough.. >> >> >> >> > Get your two CPUs in agreement about what time it is, and I bet that >> >> > the CPU stall warnings will go away. >> >> >> >> Possibly KVM related? Because the warnings show up in many test boxes >> >> running KVM and so is not likely some hardware specific issue. >> > >> > I vaguely recall seeing something recently. But let's ask the KVM and >> > timekeeping guys. >> >> >From the logs it looks like hpet (why not kvmclock?) is used for the >> clock, it should not generate such drifts since it is a global clock. >> Can you verify current_clocksource on a boot that actually failed (in >> case the clocksource is switched during runtime)? > > I've checked out the dmesg that's cited by Paul, attached. Yes it > contains lines > > [ 4.970051] Switching to clocksource hpet > > and then > > [ 7.250353] Switching to clocksource tsc > > And there is no kvm-clock lines. Oh well for this particular kernel: > Ah, tsc will certainly break on kvm if the hardware doesn't provide a constant tsc source. I'm surprised the guest kernel didn't detect it and switch back to hpet though. -- error compiling committee.c: too many arguments to function -- 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
