Re: [PATCH v1] migration/dirtyrate: make sample page count configurable

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* huangy81@chinatelecom.cn (huangy81@chinatelecom.cn) wrote:
> From: Hyman Huang(黄勇) <huangy81@chinatelecom.cn>
> 
> introduce optional sample-pages argument in calc-dirty-rate,
> making sample page count per GB configurable so that more
> accurate dirtyrate can be calculated.
> 
> Signed-off-by: Hyman Huang(黄勇) <huangy81@chinatelecom.cn>

I think this is mostly OK, so:

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

I'm curious; do you find that increasing the sample count is making much
difference to the results?

Dave

> ---
>  migration/dirtyrate.c | 32 ++++++++++++++++++++++++++++----
>  migration/dirtyrate.h |  8 +++++++-
>  qapi/migration.json   | 13 ++++++++++---
>  3 files changed, 45 insertions(+), 8 deletions(-)
> 
> diff --git a/migration/dirtyrate.c b/migration/dirtyrate.c
> index ccb9814..43a531c 100644
> --- a/migration/dirtyrate.c
> +++ b/migration/dirtyrate.c
> @@ -48,6 +48,16 @@ static bool is_sample_period_valid(int64_t sec)
>      return true;
>  }
>  
> +static bool is_sample_pages_valid(int64_t pages)
> +{
> +    if (pages < MIN_SAMPLE_PAGE_COUNT ||
> +        pages > MAX_SAMPLE_PAGE_COUNT) {
> +        return false;
> +    }
> +
> +    return true;

David is right that could be simplified; but it's OK.

> +}
> +
>  static int dirtyrate_set_state(int *state, int old_state, int new_state)
>  {
>      assert(new_state < DIRTY_RATE_STATUS__MAX);
> @@ -72,13 +82,15 @@ static struct DirtyRateInfo *query_dirty_rate_info(void)
>      info->status = CalculatingState;
>      info->start_time = DirtyStat.start_time;
>      info->calc_time = DirtyStat.calc_time;
> +    info->sample_pages = DirtyStat.sample_pages;
>  
>      trace_query_dirty_rate_info(DirtyRateStatus_str(CalculatingState));
>  
>      return info;
>  }
>  
> -static void init_dirtyrate_stat(int64_t start_time, int64_t calc_time)
> +static void init_dirtyrate_stat(int64_t start_time, int64_t calc_time,
> +                                uint64_t sample_pages)
>  {
>      DirtyStat.total_dirty_samples = 0;
>      DirtyStat.total_sample_count = 0;
> @@ -86,6 +98,7 @@ static void init_dirtyrate_stat(int64_t start_time, int64_t calc_time)
>      DirtyStat.dirty_rate = -1;
>      DirtyStat.start_time = start_time;
>      DirtyStat.calc_time = calc_time;
> +    DirtyStat.sample_pages = sample_pages;
>  }
>  
>  static void update_dirtyrate_stat(struct RamblockDirtyInfo *info)
> @@ -361,6 +374,7 @@ void *get_dirtyrate_thread(void *arg)
>      int ret;
>      int64_t start_time;
>      int64_t calc_time;
> +    uint64_t sample_pages;
>  
>      ret = dirtyrate_set_state(&CalculatingState, DIRTY_RATE_STATUS_UNSTARTED,
>                                DIRTY_RATE_STATUS_MEASURING);
> @@ -371,7 +385,8 @@ void *get_dirtyrate_thread(void *arg)
>  
>      start_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME) / 1000;
>      calc_time = config.sample_period_seconds;
> -    init_dirtyrate_stat(start_time, calc_time);
> +    sample_pages = config.sample_pages_per_gigabytes;
> +    init_dirtyrate_stat(start_time, calc_time, sample_pages);
>  
>      calculate_dirtyrate(config);
>  
> @@ -383,7 +398,8 @@ void *get_dirtyrate_thread(void *arg)
>      return NULL;
>  }
>  
> -void qmp_calc_dirty_rate(int64_t calc_time, Error **errp)
> +void qmp_calc_dirty_rate(int64_t calc_time, bool has_sample_pages,
> +                         int64_t sample_pages, Error **errp)
>  {
>      static struct DirtyRateConfig config;
>      QemuThread thread;
> @@ -404,6 +420,13 @@ void qmp_calc_dirty_rate(int64_t calc_time, Error **errp)
>          return;
>      }
>  
> +    if (has_sample_pages && !is_sample_pages_valid(sample_pages)) {
> +        error_setg(errp, "sample-pages is out of range[%d, %d].",
> +                         MIN_SAMPLE_PAGE_COUNT,
> +                         MAX_SAMPLE_PAGE_COUNT);
> +        return;
> +    }
> +
>      /*
>       * Init calculation state as unstarted.
>       */
> @@ -415,7 +438,8 @@ void qmp_calc_dirty_rate(int64_t calc_time, Error **errp)
>      }
>  
>      config.sample_period_seconds = calc_time;
> -    config.sample_pages_per_gigabytes = DIRTYRATE_DEFAULT_SAMPLE_PAGES;
> +    config.sample_pages_per_gigabytes =
> +        has_sample_pages ? sample_pages : DIRTYRATE_DEFAULT_SAMPLE_PAGES;
>      qemu_thread_create(&thread, "get_dirtyrate", get_dirtyrate_thread,
>                         (void *)&config, QEMU_THREAD_DETACHED);
>  }
> diff --git a/migration/dirtyrate.h b/migration/dirtyrate.h
> index 6ec4295..5f987e2 100644
> --- a/migration/dirtyrate.h
> +++ b/migration/dirtyrate.h
> @@ -15,7 +15,6 @@
>  
>  /*
>   * Sample 512 pages per GB as default.
> - * TODO: Make it configurable.
>   */
>  #define DIRTYRATE_DEFAULT_SAMPLE_PAGES            512
>  
> @@ -35,6 +34,12 @@
>  #define MIN_FETCH_DIRTYRATE_TIME_SEC              1
>  #define MAX_FETCH_DIRTYRATE_TIME_SEC              60
>  
> +/*
> + * Take 128 as minimum for sample dirty pages
> + */
> +#define MIN_SAMPLE_PAGE_COUNT                     128
> +#define MAX_SAMPLE_PAGE_COUNT                     4096
> +
>  struct DirtyRateConfig {
>      uint64_t sample_pages_per_gigabytes; /* sample pages per GB */
>      int64_t sample_period_seconds; /* time duration between two sampling */
> @@ -63,6 +68,7 @@ struct DirtyRateStat {
>      int64_t dirty_rate; /* dirty rate in MB/s */
>      int64_t start_time; /* calculation start time in units of second */
>      int64_t calc_time; /* time duration of two sampling in units of second */
> +    uint64_t sample_pages; /* sample pages per GB */
>  };
>  
>  void *get_dirtyrate_thread(void *arg);
> diff --git a/qapi/migration.json b/qapi/migration.json
> index 9bf0bc4..868a867 100644
> --- a/qapi/migration.json
> +++ b/qapi/migration.json
> @@ -1741,6 +1741,9 @@
>  #
>  # @calc-time: time in units of second for sample dirty pages
>  #
> +# @sample-pages: page count per GB for sample dirty pages
> +#                the default value is 512

That needs a (since 6.1) adding; I can do that during the merge.

> +#
>  # Since: 5.2
>  #
>  ##
> @@ -1748,7 +1751,8 @@
>    'data': {'*dirty-rate': 'int64',
>             'status': 'DirtyRateStatus',
>             'start-time': 'int64',
> -           'calc-time': 'int64'} }
> +           'calc-time': 'int64',
> +           'sample-pages': 'uint64'} }
>  
>  ##
>  # @calc-dirty-rate:
> @@ -1757,13 +1761,16 @@
>  #
>  # @calc-time: time in units of second for sample dirty pages
>  #
> +# @sample-pages: page count per GB for sample dirty pages
> +#                the default value is 512

That needs a (since 6.1) adding; I can do that during the merge; as does
that.

> +#
>  # Since: 5.2
>  #
>  # Example:
> -#   {"command": "calc-dirty-rate", "data": {"calc-time": 1} }
> +#   {"command": "calc-dirty-rate", "data": {"calc-time": 1, 'sample-pages': 512} }
>  #
>  ##
> -{ 'command': 'calc-dirty-rate', 'data': {'calc-time': 'int64'} }
> +{ 'command': 'calc-dirty-rate', 'data': {'calc-time': 'int64', '*sample-pages': 'int'} }
>  
>  ##
>  # @query-dirty-rate:
> -- 
> 1.8.3.1
> 
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK