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

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

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().