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    SubjectRe: [kvm-devel] Use virtual cpu accounting if available for guest times.
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    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@de.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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