Re: [PATCH v5 09/12] migration/dirtyrate: Implement get_sample_page_period() and block_sample_page_period()

[David Edmondson]

On Thursday, 2020-08-27 at 16:01:37 +08, Zheng Chuan wrote:

> On 2020/8/26 18:17, David Edmondson wrote:
>> On Monday, 2020-08-24 at 17:14:37 +08, Chuan Zheng wrote:
>> 
>>> Implement get_sample_page_period() and set_sample_page_period() to
>>> sleep specific time between sample actions.
>>>
>>> Signed-off-by: Chuan Zheng <zhengchuan@huawei.com>
>>> ---
>>>  migration/dirtyrate.c | 24 ++++++++++++++++++++++++
>>>  migration/dirtyrate.h |  2 ++
>>>  2 files changed, 26 insertions(+)
>>>
>>> diff --git a/migration/dirtyrate.c b/migration/dirtyrate.c
>>> index bd398b7..d1c0a78 100644
>>> --- a/migration/dirtyrate.c
>>> +++ b/migration/dirtyrate.c
>>> @@ -28,6 +28,30 @@
>>>  static int CalculatingState = DIRTY_RATE_STATUS_UNSTARTED;
>>>  static struct DirtyRateStat DirtyStat;
>>>  
>>> +static int64_t set_sample_page_period(int64_t msec, int64_t initial_time)
>>> +{
>>> +    int64_t current_time;
>>> +
>>> +    current_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
>>> +    if ((current_time - initial_time) >= msec) {
>>> +        msec = current_time - initial_time;
>>> +    } else {
>>> +        g_usleep((msec + initial_time - current_time) * 1000);
>>> +    }
>>> +
>>> +    return msec;
>>> +}
>>> +
>>> +static int64_t get_sample_page_period(int64_t sec)
>>> +{
>>> +    if (sec <= MIN_FETCH_DIRTYRATE_TIME_SEC ||
>> 
>> Shouldn't the minimum value be allowed?
>> 
>> That is, this test should be "sec < MIN_FETCH_DIRTYRATE_TIME_SEC" and
>> MIN_FETCH_DIRTYRATE_TIME_SEC should be 1.
>> 
> Well, Actually we could measure dirtyrate within duration below 1s, like 0.5s.
> Howerver, I am reconsider that maybe taking 0.5s as 
> MIN_FETCH_DIRTYRATE_TIME_SEC is better in case of someone to do nasty thing 
> like setting
> a meaningless time duration which is close to 0:)

I think that a minimum of 1 second is fine. My concern is only that if
you say "the minimum is X" but then don't let me choose X, it seems
weird.

>>> +        sec > MAX_FETCH_DIRTYRATE_TIME_SEC) {
>>> +        sec = DEFAULT_FETCH_DIRTYRATE_TIME_SEC;
>>> +    }
>>> +
>>> +    return sec;
>>> +}
>>> +
>>>  static int dirtyrate_set_state(int *state, int old_state, int new_state)
>>>  {
>>>      assert(new_state < DIRTY_RATE_STATUS__MAX);
>>> diff --git a/migration/dirtyrate.h b/migration/dirtyrate.h
>>> index 41bc264..50a5636 100644
>>> --- a/migration/dirtyrate.h
>>> +++ b/migration/dirtyrate.h
>>> @@ -51,6 +51,8 @@
>>>  
>>>  /* Take 1s as default for calculation duration */
>>>  #define DEFAULT_FETCH_DIRTYRATE_TIME_SEC          1
>>> +#define MIN_FETCH_DIRTYRATE_TIME_SEC              0
>>> +#define MAX_FETCH_DIRTYRATE_TIME_SEC              60
>>>  
>>>  struct DirtyRateConfig {
>>>      uint64_t sample_pages_per_gigabytes; /* sample pages per GB */
>>> -- 
>>> 1.8.3.1
>> 
>> dme.
>> 

dme.
-- 
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