linux-kernel - Re: [kvm-devel] Use virtual cpu accounting if available for guest times.

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Date:	Fri, 19 Oct 2007 11:57:36 -0500
From:	Hollis Blanchard <hollisb@...ibm.com>
To:	Christian Borntraeger <borntraeger@...ibm.com>
Cc:	Avi Kivity <avi@...ranet.com>,
	kvm-devel <kvm-devel@...ts.sourceforge.net>,
	Laurent Vivier <Laurent.Vivier@...l.net>,
	linux-kernel@...r.kernel.org
Subject: Re: [kvm-devel] Use virtual cpu accounting if available for guest
	times.

On Thu, 2007-10-18 at 14:39 +0200, Christian Borntraeger wrote:
> Avi,
> 
> ppc and s390 offer the possibility to track process times precisely
> by looking at cpu timer on every context switch, irq, softirq etc.
> We can use that infrastructure as well for guest time accounting.
> We need to account the used time before we change the state. 
> This patch adds a call to account_system_vtime to kvm_guest_enter
> and kvm_guest exit. If CONFIG_VIRT_CPU_ACCOUNTING is not set,
> account_system_vtime is defined in hardirq.h as an empty function,
> which means this patch does not change the behaviour on other
> platforms.
> 
> I compile tested this patch on x86 and function tested the patch on
> s390.
> 
> Avi, please apply.
> 
> 
> Signed-off-by: Christian Borntraeger <borntraeger@...ibm.com>
> 
> ---
>  drivers/kvm/kvm.h |    3 +++
>  1 file changed, 3 insertions(+)
> 
> Index: kvm/drivers/kvm/kvm.h
> ===================================================================
> --- kvm.orig/drivers/kvm/kvm.h
> +++ kvm/drivers/kvm/kvm.h
> @@ -7,6 +7,7 @@
>   */
> 
>  #include <linux/types.h>
> +#include <linux/hardirq.h>
>  #include <linux/list.h>
>  #include <linux/mutex.h>
>  #include <linux/spinlock.h>
> @@ -669,11 +670,13 @@ __init void kvm_arch_init(void);
> 
>  static inline void kvm_guest_enter(void)
>  {
> +	account_system_vtime(current);
>  	current->flags |= PF_VCPU;
>  }
> 
>  static inline void kvm_guest_exit(void)
>  {
> +	account_system_vtime(current);
>  	current->flags &= ~PF_VCPU;
>  }

I don't understand. Should kvm_guest_exit() be calling
account_user_vtime() (instead of account_system_vtime())?

-- 
Hollis Blanchard
IBM Linux Technology Center

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