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

[Zheng Chuan]

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:)

>> +        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.
>