From: Paolo Bonzini <pbonzini@redhat.com>
To: Rik van Riel <riel@redhat.com>, Wanpeng Li <kernellwp@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>,
Ingo Molnar <mingo@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Wanpeng Li <wanpeng.li@hotmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
Radim Krcmar <rkrcmar@redhat.com>, Mike Galbraith <efault@gmx.de>
Subject: Re: [PATCH] time,virt: resync steal time when guest & host lose sync
Date: Fri, 12 Aug 2016 18:33:54 +0200 [thread overview]
Message-ID: <c5405116-91ca-23cc-6855-0b9109f1d55d@redhat.com> (raw)
In-Reply-To: <20160810125212.78564dc2@annuminas.surriel.com>
On 10/08/2016 18:52, Rik van Riel wrote:
> Paolo, what is your opinion on this issue?
>
> I can think of all kinds of ways in which guest and host might lose
> sync with steal time, from uninitialized values at boot, to guest
> pause, followed by save to disk, and reload, to live migration, to...
Guest and host _cannot_ lose sync because there is only one copy of the
values. When the host wants to update the steal time value it just
reads the old value and writes the new value. There cannot be a guest
pause, save to disk, live migration or whatever between these two steps
(and uninitialized values at boot are not how percpu values work).
Your hypothesis of lost ticks makes the most sense to me, and then
changing the argument to ULONG_MAX is the right thing to do.
Paolo
next prev parent reply other threads:[~2016-08-12 16:34 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-13 14:50 [GIT PULL] cputime fixes and cleanups Frederic Weisbecker
2016-07-13 14:50 ` [PATCH 1/5] sched,time: Count actually elapsed irq & softirq time Frederic Weisbecker
2016-07-14 10:37 ` [tip:timers/nohz] sched/cputime: " tip-bot for Rik van Riel
2016-08-09 3:59 ` [PATCH 1/5] sched,time: " Wanpeng Li
2016-08-09 14:06 ` Rik van Riel
2016-08-09 23:07 ` Wanpeng Li
2016-08-10 7:51 ` Wanpeng Li
2016-08-09 23:25 ` Wanpeng Li
2016-08-09 23:31 ` Wanpeng Li
2016-08-09 23:35 ` Wanpeng Li
2016-08-09 23:39 ` Wanpeng Li
2016-08-10 5:07 ` Rik van Riel
2016-08-10 6:33 ` Wanpeng Li
2016-08-10 16:52 ` [PATCH] time,virt: resync steal time when guest & host lose sync Rik van Riel
2016-08-11 10:11 ` Wanpeng Li
2016-08-12 2:44 ` Rik van Riel
2016-08-12 7:09 ` Wanpeng Li
2016-08-12 15:58 ` Rik van Riel
2016-08-13 15:36 ` Frederic Weisbecker
2016-08-15 8:53 ` Wanpeng Li
2016-08-15 11:38 ` Wanpeng Li
2016-08-15 15:00 ` Rik van Riel
2016-08-15 22:19 ` Wanpeng Li
2016-08-16 1:31 ` Wanpeng Li
2016-08-16 2:11 ` Rik van Riel
2016-08-16 6:54 ` Wanpeng Li
2016-08-16 14:01 ` Rik van Riel
2016-08-16 23:08 ` Wanpeng Li
2016-08-12 16:33 ` Paolo Bonzini [this message]
2016-08-12 17:23 ` Rik van Riel
2016-08-13 7:18 ` Paolo Bonzini
2016-08-13 8:42 ` Ingo Molnar
2016-08-14 1:50 ` Rik van Riel
2016-08-18 8:23 ` Wanpeng Li
2016-07-13 14:50 ` [PATCH 2/5] nohz,cputime: Replace VTIME_GEN irq time code with IRQ_TIME_ACCOUNTING code Frederic Weisbecker
2016-07-14 10:37 ` [tip:timers/nohz] sched/cputime: " tip-bot for Rik van Riel
2016-07-13 14:50 ` [PATCH 3/5] sched: Complete cleanup of old vtime gen irqtime accounting Frederic Weisbecker
2016-07-14 10:38 ` [tip:timers/nohz] sched/cputime: Clean up the old vtime gen irqtime accounting completely tip-bot for Frederic Weisbecker
2016-07-13 14:50 ` [PATCH 4/5] sched: Reorganize vtime native irqtime accounting headers Frederic Weisbecker
2016-07-14 10:38 ` [tip:timers/nohz] sched/cputime: " tip-bot for Frederic Weisbecker
2016-07-13 14:50 ` [PATCH 5/5] time: Drop local_irq_save/restore from irqtime_account_irq Frederic Weisbecker
2016-07-14 10:38 ` [tip:timers/nohz] sched/cputime: Drop local_irq_save/restore from irqtime_account_irq() tip-bot for Rik van Riel
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