From: Peter Zijlstra <peterz@infradead.org>
To: Wanpeng Li <kernellwp@gmail.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Wanpeng Li <wanpeng.li@hotmail.com>,
Ingo Molnar <mingo@kernel.org>, Rik van Riel <riel@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Frederic Weisbecker <fweisbec@gmail.com>,
Paolo Bonzini <pbonzini@redhat.com>, Radim <rkrcmar@redhat.com>
Subject: Re: [PATCH] sched/cputime: add steal clock warps handling during cpu hotplug
Date: Thu, 2 Jun 2016 14:00:23 +0200 [thread overview]
Message-ID: <20160602120023.GC3190@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <1464868639-8924-1-git-send-email-wanpeng.li@hotmail.com>
On Thu, Jun 02, 2016 at 07:57:19PM +0800, Wanpeng Li wrote:
> From: Wanpeng Li <wanpeng.li@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. both guest and host are latest 4.7-rc1, 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 warps and then steal_jiffies overflow, this patch align
> prev_steal_time to the new steal clock timestamp, in order to avoid
> overflow and st stuff can continue to work.
I would rather suggest fixing the steal clock thing to not jump like
that; is that at all possible?
next prev parent reply other threads:[~2016-06-02 12:00 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-02 11:57 [PATCH] sched/cputime: add steal clock warps handling during cpu hotplug Wanpeng Li
2016-06-02 12:00 ` Peter Zijlstra [this message]
2016-06-02 13:59 ` Rik van Riel
2016-06-03 5:34 ` Wanpeng Li
2016-06-06 13:40 ` Paolo Bonzini
2016-06-06 22:42 ` Wanpeng Li
2016-06-07 1:24 ` Rik van Riel
2016-06-07 7:31 ` Paolo Bonzini
2016-06-07 7:35 ` Wanpeng Li
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