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Re: [Qemu-devel] Re: [RFC: 0/2] patch for QEMU HPET periodic timer emula
From: |
Jan Kiszka |
Subject: |
Re: [Qemu-devel] Re: [RFC: 0/2] patch for QEMU HPET periodic timer emulation to alleviate time drift |
Date: |
Mon, 07 Feb 2011 16:08:55 +0100 |
User-agent: |
Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666 |
On 2011-02-07 16:01, Anthony Liguori wrote:
> 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);
Or just use QEMUTimerCB directly. BTW, QEMUPeriodicTimer* would probably
be more consistent with the existing naming scheme.
>
> 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);
>
Looks like a plan.
Jan
--
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux
- Re: [Qemu-devel] Re: [RFC: 0/2] patch for QEMU HPET periodic timer emulation to alleviate time drift, (continued)
- Re: [Qemu-devel] Re: [RFC: 0/2] patch for QEMU HPET periodic timer emulation to alleviate time drift, Jan Kiszka, 2011/02/07
- Re: [Qemu-devel] Re: [RFC: 0/2] patch for QEMU HPET periodic timer emulation to alleviate time drift, Anthony Liguori, 2011/02/07
- Re: [Qemu-devel] Re: [RFC: 0/2] patch for QEMU HPET periodic timer emulation to alleviate time drift, Jan Kiszka, 2011/02/07
- Re: [Qemu-devel] Re: [RFC: 0/2] patch for QEMU HPET periodic timer emulation to alleviate time drift, Anthony Liguori, 2011/02/07
- Re: [Qemu-devel] Re: [RFC: 0/2] patch for QEMU HPET periodic timer emulation to alleviate time drift, Jan Kiszka, 2011/02/07
- Re: [Qemu-devel] Re: [RFC: 0/2] patch for QEMU HPET periodic timer emulation to alleviate time drift, Anthony Liguori, 2011/02/07
- Re: [Qemu-devel] Re: [RFC: 0/2] patch for QEMU HPET periodic timer emulation to alleviate time drift,
Jan Kiszka <=
- Re: [Qemu-devel] Re: [RFC: 0/2] patch for QEMU HPET periodic timer emulation to alleviate time drift, Avi Kivity, 2011/02/07
- Re: [Qemu-devel] Re: [RFC: 0/2] patch for QEMU HPET periodic timer emulation to alleviate time drift, Jan Kiszka, 2011/02/07
- Re: [Qemu-devel] Re: [RFC: 0/2] patch for QEMU HPET periodic timer emulation to alleviate time drift, Avi Kivity, 2011/02/07
- Re: [Qemu-devel] Re: [RFC: 0/2] patch for QEMU HPET periodic timer emulation to alleviate time drift, Anthony Liguori, 2011/02/07
- Re: [Qemu-devel] Re: [RFC: 0/2] patch for QEMU HPET periodic timer emulation to alleviate time drift, Avi Kivity, 2011/02/08
- Re: [Qemu-devel] Re: [RFC: 0/2] patch for QEMU HPET periodic timer emulation to alleviate time drift, Jan Kiszka, 2011/02/07
- Re: [Qemu-devel] Re: [RFC: 0/2] patch for QEMU HPET periodic timer emulation to alleviate time drift, Avi Kivity, 2011/02/07
- Re: [Qemu-devel] Re: [RFC: 0/2] patch for QEMU HPET periodic timer emulation to alleviate time drift, Anthony Liguori, 2011/02/07
- Re: [Qemu-devel] Re: [RFC: 0/2] patch for QEMU HPET periodic timer emulation to alleviate time drift, Avi Kivity, 2011/02/07
- Re: [Qemu-devel] Re: [RFC: 0/2] patch for QEMU HPET periodic timer emulation to alleviate time drift, Jan Kiszka, 2011/02/07