Re: [Xen-devel] [PATCH] use INT64_MAX as max expiration

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 14.03.12 at 03:54, "Zhang, Yang Z" <yang.z.zhang@xxxxxxxxx> wrote:
> Currently, the max expiration time is 2147483647ns(INT32_MAX ns). This is 
> enough when guest is busy, but when guest is idle, the next timer will be 
> later than INT32_MAX ns. And those meaningless alarm will harm the pkg 
> C-state.

A wakeup every 2s can't be that harmful.

> Signed-off-by: Yang Zhang <yang.z.zhang@xxxxxxxxx>
> ---
>  vl.c |    6 +++---
>  1 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/vl.c b/vl.c
> index be8587a..40486eb 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -1410,8 +1410,8 @@ static int64_t qemu_next_deadline(void)
>          delta = active_timers[QEMU_TIMER_VIRTUAL]->expire_time -
>                       qemu_get_clock(vm_clock);
>      } else {
> -        /* To avoid problems with overflow limit this to 2^32.  */
> -        delta = INT32_MAX;
> +        /* To avoid problems with overflow limit this to 2^64 - 1000.  */
> +        delta = INT64_MAX - 1000;

This looks rather arbitrary.

Jan

>      }
> 
>      if (delta < 0)
> @@ -1427,7 +1427,7 @@ static uint64_t qemu_next_deadline_dyntick(void)
>      int64_t rtdelta;
> 
>      if (use_icount)
> -        delta = INT32_MAX;
> +        delta = INT64_MAX;
>      else
>          delta = (qemu_next_deadline() + 999) / 1000;
> 
> --
> 1.7.1
> 
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> Xen-devel@xxxxxxxxxxxxx 
> http://lists.xen.org/xen-devel 




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