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...@hotmail.com> >> >> 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 <mi...@kernel.org> >> Cc: Peter Zijlstra (Intel) <pet...@infradead.org> >> Cc: Rik van Riel <r...@redhat.com> >> Cc: Thomas Gleixner <t...@linutronix.de> >> Cc: Frederic Weisbecker <fweis...@gmail.com> >> Cc: Paolo Bonzini <pbonz...@redhat.com> >> Cc: Radim <rkrc...@redhat.com> >> Signed-off-by: Wanpeng Li <wanpeng...@hotmail.com> > > Reviewed-by: Rik van Riel <r...@redhat.com>
Sorry for being late---again, I'd like to give a shot to a fix in KVM guest code. Paolo
