On Mon, 2016-06-06 at 15:44 +0200, Paolo Bonzini wrote: > > On 03/06/2016 15:10, Rik van Riel wrote: > > > > On Fri, 2016-06-03 at 13:21 +0800, Wanpeng Li wrote: > > > > > > From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx> > > > > > > I observed that sometimes st is 100% instantaneous, then idle is > > > 100% > > > even if there is a cpu hog on the guest cpu after the cpu hotplug > > > comes > > > back(N.B. this can not always be readily reproduced). I add trace > > > to > > > capture it as below: > > > > > > cpuhp/1-12 [001] d.h1 167.461657: account_process_tick: > > > steal = > > > 1291385514, prev_steal_time = 0 > > > cpuhp/1-12 [001] d.h1 167.461659: account_process_tick: > > > steal_jiffies = 1291 > > > <idle>-0 [001] d.h1 167.462663: account_process_tick: steal > > > = > > > 18732255, prev_steal_time = 1291000000 > > > <idle>-0 [001] d.h1 167.462664: account_process_tick: > > > steal_jiffies = 18446744072437 > > > > > > The steal clock warp and then steal_jiffies overflow. > > > > > > Rik also pointed out to me: > > > > > > > > > > > > > > > I have seen stuff like that with live migration too, in the > > > > past > > > This patch adds steal clock warp handling by a safe threshold to > > > only > > > apply steal times that are positive and smaller than one second > > > (as > > > long as nohz_full has the one second timer tick left), ignoring > > > intervals > > > that are negative or longer than a second, and using those to > > > sync > > > up > > > the guest with the host. > > > > > > Cc: Ingo Molnar <mingo@xxxxxxxxxx> > > > Cc: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> > > > Cc: Rik van Riel <riel@xxxxxxxxxx> > > > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > > > Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx> > > > Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx> > > > Cc: Radim <rkrcmar@xxxxxxxxxx> > > > Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx> > > Reviewed-by: Rik van Riel <riel@xxxxxxxxxx> > Sorry for being late---again, I'd like to give a shot to a fix in KVM > guest code. This is in the guest code. Do you mean a fix on the host side? -- All Rights Reversed.
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