From mboxrd@z Thu Jan  1 00:00:00 1970
From: Rik van Riel <riel@redhat.com>
Subject: Re: [PATCH v5 3/3] sched/cputime: Add steal time support to full
 dynticks CPU time accounting
Date: Wed, 08 Jun 2016 15:05:00 -0400
Message-ID: <1465412700.4639.10.camel@redhat.com>
References: <1465355110-21714-1-git-send-email-wanpeng.li@hotmail.com>
	 <1465355110-21714-3-git-send-email-wanpeng.li@hotmail.com>
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Cc: Wanpeng Li <wanpeng.li@hotmail.com>,
	Ingo Molnar <mingo@kernel.org>,
	"Peter Zijlstra (Intel)" <peterz@infradead.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Radim =?UTF-8?Q?Kr=C4=8Dm=C3=A1=C5=99?= <rkrcmar@redhat.com>
To: Wanpeng Li <kernellwp@gmail.com>, linux-kernel@vger.kernel.org,
	kvm@vger.kernel.org
Return-path: <linux-kernel-owner@vger.kernel.org>
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List-Id: kvm.vger.kernel.org


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On Wed, 2016-06-08 at 11:05 +0800, Wanpeng Li wrote:
>=C2=A0
> @@ -681,12 +681,17 @@ static cputime_t vtime_delta(struct task_struct
> *tsk)
> =C2=A0static cputime_t get_vtime_delta(struct task_struct *tsk)
> =C2=A0{
> =C2=A0	unsigned long now =3D READ_ONCE(jiffies);
> -	unsigned long delta =3D now - tsk->vtime_snap;
> +	cputime_t delta_time, steal_time;
> =C2=A0
> +	steal_time =3D
> jiffies_to_cputime(steal_account_process_tick());
> +	delta_time =3D jiffies_to_cputime(now - tsk->vtime_snap);
> =C2=A0	WARN_ON_ONCE(tsk->vtime_snap_whence =3D=3D VTIME_INACTIVE);
> =C2=A0	tsk->vtime_snap =3D now;
> =C2=A0
> -	return jiffies_to_cputime(delta);
> +	if (steal_time < delta_time)
> +		delta_time -=3D steal_time;
> +
> +	return delta_time;
> =C2=A0}

This isn't right.

If steal_time is equal to or larger than delta_time,
get_vtime_delta needs to return 0, not delta_time.

Otherwise the same time will be counted twice.

--=20
All rights reversed

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