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Re: [PATCH v5 11/12] migration/dirtyrate: Implement qmp_cal_dirty_rate()
From: |
David Edmondson |
Subject: |
Re: [PATCH v5 11/12] migration/dirtyrate: Implement qmp_cal_dirty_rate()/qmp_get_dirty_rate() function |
Date: |
Thu, 27 Aug 2020 14:07:05 +0100 |
On Thursday, 2020-08-27 at 20:55:51 +08, Zheng Chuan wrote:
> On 2020/8/27 19:58, David Edmondson wrote:
>> On Thursday, 2020-08-27 at 17:34:13 +08, Zheng Chuan wrote:
>>
>>>>> + /*
>>>>> + * Only support query once for each calculation,
>>>>> + * reset as DIRTY_RATE_STATUS_UNSTARTED after query
>>>>> + */
>>>>> + (void)dirtyrate_set_state(&CalculatingState, CalculatingState,
>>>>> + DIRTY_RATE_STATUS_UNSTARTED);
>>>>
>>>> Is there a reason for this restriction? Removing it would require
>>>> clarifying the state model, I suppose.
>>>>
>>> We only support query once for each calculation.
>>> Otherwise, it could always query dirtyrate, but maybe the dirtyrate is
>>> calculated
>>> long time ago.
>>
>> There's nothing in the current interface that prevents this from being
>> the case already - the caller could initiate a 1 second sample, then
>> wait 24 hours to query the result.
>>
>> Obviously this would generally be regarded as "d'oh - don't do that",
>> but the same argument would apply if the caller is allowed to query the
>> results multiple times.
>>
>> Perhaps a complete solution would be to include information about the
>> sample period with the result. The caller could then determine whether
>> the sample is of adequate quality (sufficiently recent, taken over a
>> sufficiently long time period) for its' intended use.
>>
> You mean add timestamp when i calculate?
You already have a timestamp, though I'm not sure if it is one that is
appropriate to report to a user.
I was thinking that you would include both the start time and duration
of the sample in the output of the query-dirty-rate QMP command, as well
as the dirty rate itself. That way the caller can make a decision about
whether the data is useful.
> Actually, I do not want make it complicate for qemu code,
> maybe it could be left for user to implement both two qmp commands
> like in libvirt-api.
Sorry, I didn't understand this comment.
> On the other hand, it really bother me that we need to reset calculating state
> to make sure the state model could be restart in next calculation.
>
> For now, i put it after query_dirty_rate_info is finished as you see, it
> should not be a good idea:(
>
> Maybe it is better to initialize at the beginning of qmp_calc_dirty_rate().
>
>> dme.
>>
dme.
--
Another lonely day, no one here but me-o.
[PATCH v5 04/12] migration/dirtyrate: Add dirtyrate statistics series functions, Chuan Zheng, 2020/08/24
[PATCH v5 11/12] migration/dirtyrate: Implement qmp_cal_dirty_rate()/qmp_get_dirty_rate() function, Chuan Zheng, 2020/08/24
- Re: [PATCH v5 11/12] migration/dirtyrate: Implement qmp_cal_dirty_rate()/qmp_get_dirty_rate() function, David Edmondson, 2020/08/26
- Re: [PATCH v5 11/12] migration/dirtyrate: Implement qmp_cal_dirty_rate()/qmp_get_dirty_rate() function, Zheng Chuan, 2020/08/27
- Re: [PATCH v5 11/12] migration/dirtyrate: Implement qmp_cal_dirty_rate()/qmp_get_dirty_rate() function, David Edmondson, 2020/08/27
- Re: [PATCH v5 11/12] migration/dirtyrate: Implement qmp_cal_dirty_rate()/qmp_get_dirty_rate() function, Zheng Chuan, 2020/08/27
- Re: [PATCH v5 11/12] migration/dirtyrate: Implement qmp_cal_dirty_rate()/qmp_get_dirty_rate() function,
David Edmondson <=
- Re: [PATCH v5 11/12] migration/dirtyrate: Implement qmp_cal_dirty_rate()/qmp_get_dirty_rate() function, Zheng Chuan, 2020/08/27
- Re: [PATCH v5 11/12] migration/dirtyrate: Implement qmp_cal_dirty_rate()/qmp_get_dirty_rate() function, David Edmondson, 2020/08/27
[PATCH v5 02/12] migration/dirtyrate: add DirtyRateStatus to denote calculation status, Chuan Zheng, 2020/08/24
[PATCH v5 05/12] migration/dirtyrate: move RAMBLOCK_FOREACH_MIGRATABLE into ram.h, Chuan Zheng, 2020/08/24
[PATCH v5 01/12] migration/dirtyrate: setup up query-dirtyrate framwork, Chuan Zheng, 2020/08/24
[PATCH v5 06/12] migration/dirtyrate: Record hash results for each sampled page, Chuan Zheng, 2020/08/24