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
>
>
next prev parent 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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