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From: Paolo Bonzini <pbonzini@redhat.com>
To: Rik van Riel <riel@redhat.com>
Cc: Wanpeng Li <kernellwp@gmail.com>,
	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: Sat, 13 Aug 2016 03:18:42 -0400 (EDT)	[thread overview]
Message-ID: <974330607.1641549.1471072722360.JavaMail.zimbra@redhat.com> (raw)
In-Reply-To: <1471022601.32433.2.camel@redhat.com>

> There is one copy of paravirt_steal_clock(smp_processor_id()),
> but what keeps it in sync with this_rq()->prev_steal_time?
> 
> Is it something simple like them both being zeroed out when
> the structures are first allocated at boot time?

Yes, more precisely both of them being equal when the MSR is
written to.  They are just memory locations so they remain in
sync across pause, migration and the like, and prev_steal_time
is only ever updated with a previous value of paravirt_steal_clock().

> > 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.
> 
> I sent out a patch that just removes the parameter instead,
> and documents why steal_account_process_time can encounter
> more elapsed time than the calling functions expected.

Good, thanks!

Paolo

  reply	other threads:[~2016-08-13  7:19 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
2016-08-12 17:23               ` Rik van Riel
2016-08-13  7:18                 ` Paolo Bonzini [this message]
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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