Re: [PATCH] migration/dirtyrate: use QEMU_CLOCK_HOST to report start-time

[Markus Armbruster]

Philippe Mathieu-Daudé <philmd@linaro.org> writes:

> Hi Andrei,
>
> On 5/9/23 11:18, Andrei Gudkov via wrote:
>> Currently query-dirty-rate uses QEMU_CLOCK_REALTIME as
>> the source for start-time field. This translates to
>> clock_gettime(CLOCK_MONOTONIC), i.e. number of seconds
>> since host boot. This is not very useful. The only
>> reasonable use case of start-time I can imagine is to
>> check whether previously completed measurements are
>> too old or not. But this makes sense only if start-time
>> is reported as host wall-clock time.
>> This patch replaces source of start-time from
>> QEMU_CLOCK_REALTIME to QEMU_CLOCK_HOST.
>> Signed-off-by: Andrei Gudkov <gudkov.andrei@huawei.com>
>> ---
>>   qapi/migration.json   |  4 ++--
>>   migration/dirtyrate.c | 15 ++++++---------
>>   2 files changed, 8 insertions(+), 11 deletions(-)
>
>
>> diff --git a/migration/dirtyrate.c b/migration/dirtyrate.c
>> index bccb3515e3..0510d68765 100644
>> --- a/migration/dirtyrate.c
>> +++ b/migration/dirtyrate.c
>> @@ -259,11 +259,10 @@ static struct DirtyRateInfo 
>> *query_dirty_rate_info(void)
>>       return info;
>>   }
>>   -static void init_dirtyrate_stat(int64_t start_time,
>> -                                struct DirtyRateConfig config)
>> +static void init_dirtyrate_stat(struct DirtyRateConfig config)
>>   {
>>       DirtyStat.dirty_rate = -1;
>> -    DirtyStat.start_time = start_time;
>> +    DirtyStat.start_time = qemu_clock_get_ms(QEMU_CLOCK_HOST) / 1000;
>>       DirtyStat.calc_time = config.sample_period_seconds;
>>       DirtyStat.sample_pages = config.sample_pages_per_gigabytes;
>>   @@ -600,7 +599,7 @@ static void calculate_dirtyrate_dirty_bitmap(struct 
>> DirtyRateConfig config)
>>       record_dirtypages_bitmap(&dirty_pages, true);
>>         start_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
>> -    DirtyStat.start_time = start_time / 1000;
>> +    DirtyStat.start_time = qemu_clock_get_ms(QEMU_CLOCK_HOST) / 1000;
>
> You can directly use qemu_clock_get_us().

Andrei, care to respin?