[Xen-devel] Re: [PATCH] cpu idle ticks show twice in xen pvm guest

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

On 10/10/2011 08:53 AM, Konrad Rzeszutek Wilk wrote:
> On Wed, Oct 05, 2011 at 10:11:58PM -0700, Zhenzhong Duan wrote:
>> Run below test on xen pvm.
>> # x=$(cat /proc/stat | grep cpu0 | awk '{print $5}') && sleep 60  \
>> && y=$(cat /proc/stat | grep cpu0 | awk '{print $5}') \
>> && echo -e  "X:$x\nY:$y\nIDLE:" $(echo "scale=3; ($y-$x)/6000*100" | bc)
>>
>> @ X:58562301
>> @ Y:58574282
>> @ IDLE: 199.600
>>
>> Normal idle percent should be around 100%.
>> xen_timer_interrupt called account_idle_ticks to account hypervisor stolen 
>> idle ticks 
>> but these ticks will be accounted again when idle ticks restarted.
>>
>> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@xxxxxxxxxx>
>> Signed-off-by: Joe Jin <joe.jin@xxxxxxxxxx>
> Please in the future also CC the maintainers (you can get that using
> the scripts/get_maintainer.pl).
>
> Jeremy, any thoughts?

Does this affect the accounting of stolen ticks?  If it does, that's not
necessarily a showstopper for this patch, but we'll need to do some more
thinking about it.  Certainly, accurate accounting for idleness is
important.

    J

>> diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
>> index 163b467..5dcbc91 100644
>> --- a/arch/x86/xen/time.c
>> +++ b/arch/x86/xen/time.c
>> @@ -151,7 +151,6 @@ static void do_stolen_accounting(void)
>>  
>>      ticks = iter_div_u64_rem(blocked, NS_PER_TICK, &blocked);
>>      __this_cpu_write(xen_residual_blocked, blocked);
>> -    account_idle_ticks(ticks);
>>  }
>>  
>>  /* Get the TSC speed from Xen */
>> --
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