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From: Anthony Liguori <anthony@codemonkey.ws>
To: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Anthony Liguori <anthony@codemonkey.ws>,
	qemu-devel <qemu-devel@nongnu.org>,
	Glauber Costa <glommer@redhat.com>,
	Ulrich Obergfell <uobergfe@redhat.com>, kvm <kvm@vger.kernel.org>,
	Avi Kivity <avi@redhat.com>
Subject: Re: [Qemu-devel] Re: [RFC: 0/2] patch for QEMU HPET periodic timer emulation to alleviate time drift
Date: Mon, 07 Feb 2011 09:01:00 -0600	[thread overview]
Message-ID: <4D50092C.1080109@codemonkey.ws> (raw)
In-Reply-To: <4D500872.3070506@siemens.com>

On 02/07/2011 08:57 AM, Jan Kiszka wrote:
> There should rather be a special vmstate struct for PeriodicTimer, just
> like we already have for normal timers.
>    

Agreed.

>> It's convenient because then if we lose ticks in the PeriodicTimer
>> layer, the devices have instance access to that info.  When you do a
>> read() from timerfd, it returns the number of coalesced events.  That's
>> the interface I had in my mind.
>>
>> We could just add a getter for PeriodicTimer and it would serve the same
>> purpose.
>>      
> I'm still not sure what the device model is supposed to do with that
> information. I think at could remain private to the PeriodicTimer
> implementation (unless we want to dump some stats or such).
>    

Yeah, I've been thinking about it too and I think I agree with you.

So here's the new proposal:

typedef struct PeriodicTimer PeriodicTimer;

/**
  * @accumulated_ticks:  the number of unacknowledged ticks in total 
since the creation of the timer
  **/
typedef void (PeriodicTimerFunc)(void *opaque);

PeriodicTimer *periodic_timer_new(PeriodicTimerFunc *cb, void *opaque);

void periodic_timer_mod(PeriodicTimer *timer, int64_t interval, TimeUnit 
unit);

/**
  * @policy: the drift catch-up policy
  *                DRIFT_COMP_FAST, deliver next tick as soon as any 
tick is acknowledged if accumulated_ticks > 1
  *                DRIFT_COMP_NONE, do not change interval regardless of 
accumulated ticks
  *                DRIFT_COMP_GRADUAL, shorten interval by half until 
accumulated_ticks <= 1
  */
void periodic_timer_set_policy(PeriodicTimer *timer, 
DriftCompensationPolicy policy);

/**
  * @ticks: number of ticks to acknowledge that are currently outstanding.
  **/
void periodic_timer_ack(PeriodicTimer *timer, int ticks);

int periodic_timer_get_accumulated_ticks(PeriodicTimer *timer);

Regards,

Anthony Liguori

> Jan
>
>    


  reply	other threads:[~2011-02-07 15:03 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <480481933.225059.1296734409954.JavaMail.root@zmail07.collab.prod.int.phx2.redhat.com>
2011-02-03 13:43 ` [RFC: 0/2] patch for QEMU HPET periodic timer emulation to alleviate time drift Ulrich Obergfell
2011-02-03 15:28   ` Jan Kiszka
2011-02-03 20:07     ` [Qemu-devel] " Anthony Liguori
2011-02-03 21:24       ` Jan Kiszka
2011-02-04  2:06         ` Anthony Liguori
2011-02-04  8:56           ` Jan Kiszka
2011-02-07 12:34             ` Avi Kivity
2011-02-07 13:11               ` Anthony Liguori
2011-02-07 13:14                 ` Avi Kivity
2011-02-07 13:23                   ` Anthony Liguori
2011-02-07 13:34                     ` Avi Kivity
2011-02-07 13:41                     ` Gleb Natapov
2011-02-07 13:46                       ` Avi Kivity
2011-02-07 13:48                         ` Gleb Natapov
2011-02-07 13:51                           ` Avi Kivity
2011-02-07 13:54                             ` Gleb Natapov
2011-02-07 14:10                     ` Jan Kiszka
2011-02-07 14:28                       ` Anthony Liguori
2011-02-07 14:43                         ` Jan Kiszka
2011-02-07 14:54                           ` Anthony Liguori
2011-02-07 14:57                             ` Jan Kiszka
2011-02-07 15:01                               ` Anthony Liguori [this message]
2011-02-07 15:08                                 ` Jan Kiszka
2011-02-07 15:13                                 ` Avi Kivity
2011-02-07 15:17                                   ` Jan Kiszka
2011-02-07 15:29                                     ` Avi Kivity
2011-02-07 19:30                                       ` Anthony Liguori
2011-02-08  9:11                                         ` Avi Kivity
2011-02-07 15:20                                   ` Jan Kiszka
2011-02-07 15:30                                     ` Avi Kivity
2011-02-07 19:28                                     ` Anthony Liguori
2011-02-07 14:58                             ` Avi Kivity
2011-02-07 15:01                               ` Jan Kiszka
2011-02-07 15:08                                 ` Avi Kivity
2011-02-07 15:14                                   ` Jan Kiszka
2011-02-07 15:16                                     ` Avi Kivity
2011-02-07 15:22                                   ` Anthony Liguori
2011-02-07 15:18                               ` Anthony Liguori
2011-02-04  9:52           ` Ulrich Obergfell
2011-02-07 10:44       ` Ulrich Obergfell
2011-02-07 13:24       ` Anthony Liguori

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