Re: [Qemu-devel] [PATCH 3/4] Enable qemu-timer dynticks for Solaris

[Paolo Bonzini]

Il 27/03/2012 17:08, Jan Kiszka ha scritto:
>>> +#if defined(__sun__)
>>> +    if (timer_create(CLOCK_HIGHRES, &ev, &host_timer)) {
>>> +#else
>>>      if (timer_create(CLOCK_REALTIME, &ev, &host_timer)) {
>>> +#endif
>>
>> This should be #ifdef CLOCK_HIGHRES.
> 
> Are we sure about this is and will remain equivalent and correct?
> 
> Also, I found some man page that says CLOCK_HIGHRES is non-adjustable
> while CLOCK_REALTIME is. That should make a difference in QEMU.

Right, that's why I CCed you but then I forgot to ask the question.

Does QEMU rely on CLOCK_REALTIME when "-rtc clock=host" is in use?  A
monotonic clock would work better when CLOCK_REALTIME jumps backwards
(DST->solar).  If the jump goes unnoticed, the alarm timer would have no
timeout for an hour or so.

Of course the opposite is true when going from solar time to DST; you
move the realtime clock one hour forward and, with CLOCK_MONOTONIC, a
host_clock timer to trigger an hour too late.

Paolo