Re: [Xen-devel] [Xen-users] Re: Xen 4 TSC problems

[Keir Fraser <keir.xen@xxxxxxxxx>]

We have no idea yet whether this workaround even does any good.

 -- Keir

On 18/10/2012 14:45, "Philippe.Simonet@xxxxxxxxxxxx"
<Philippe.Simonet@xxxxxxxxxxxx> wrote:

> in the meantime, it would be cool to have a kernel boot parameter that could
> disable this wrapping'
> correction' ? like <check-timer-wrap=false>
> 
>> -----Original Message-----
>> From: xen-devel-bounces@xxxxxxxxxxxxx [mailto:xen-devel-
>> bounces@xxxxxxxxxxxxx] On Behalf Of Ian Campbell
>> Sent: Thursday, October 18, 2012 9:40 AM
>> To: Keir Fraser
>> Cc: Jeremy Fitzhardinge; xen-devel@xxxxxxxxxxxxxxxxxxx; Dan
>> Magenheimer; Mauro; Olivier Hanesse; Jan Beulich; Xen Users; Mark Adams
>> Subject: Re: [Xen-devel] [Xen-users] Re: Xen 4 TSC problems
>> 
>> On Wed, 2012-10-17 at 17:15 +0100, Keir Fraser wrote:
>>> @@ -540,6 +541,14 @@ static void plt_overflow(void *unused)
>>>          plt_wrap = __read_platform_stime(plt_stamp64 + plt_mask + 1);
>>>          if ( ABS(plt_wrap - now) > ABS(plt_now - now) )
>>>              break;
>>> +        rdtscll(tsc);
>>> +        printk("XXX plt_overflow: plt_now=%"PRIx64" plt_wrap=%"PRIx64
>>> +               " now=%"PRIx64" old_stamp=%"PRIx64" new_stamp=%"PRIx64
>>> +               " plt_stamp64=%"PRIx64" plt_mask=%"PRIx64
>>> +               " tsc=%"PRIx64" tsc_stamp=%"PRIx64"\n",
>>> +               plt_now, plt_wrap, now, old_stamp, plt_stamp, plt_stamp64,
>>> +               plt_mask, tsc, this_cpu(cpu_time).local_tsc_stamp);
>>> +        break;
>> 
>> Is the break here, making the following update to plt_stamp64 dead code
>> deliberate?
>> 
>>>          plt_stamp64 += plt_mask + 1;
>>>      }
>>>      if ( i != 0 )
>> 
>> Ian.
>> 
>> 
>> 
>> _______________________________________________
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>> Xen-devel@xxxxxxxxxxxxx
>> http://lists.xen.org/xen-devel



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