Re: [Qemu-devel] [PATCH 04/12] migration: introduce migration_update_rates

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

* guangrong.xiao@gmail.com (guangrong.xiao@gmail.com) wrote:
> From: Xiao Guangrong <xiaoguangrong@tencent.com>
> 
> It is used to slightly clean the code up, no logic is changed

Actually, there is a slight change; iterations_prev is always updated
when previously it was only updated with xbzrle on; still the change
makes more sense.


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

> Signed-off-by: Xiao Guangrong <xiaoguangrong@tencent.com>
> ---
>  migration/ram.c | 35 ++++++++++++++++++++++-------------
>  1 file changed, 22 insertions(+), 13 deletions(-)
> 
> diff --git a/migration/ram.c b/migration/ram.c
> index dd1283dd45..ee03b28435 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -1130,6 +1130,25 @@ uint64_t ram_pagesize_summary(void)
>      return summary;
>  }
>  
> +static void migration_update_rates(RAMState *rs, int64_t end_time)
> +{
> +    uint64_t iter_count = rs->iterations - rs->iterations_prev;
> +
> +    /* calculate period counters */
> +    ram_counters.dirty_pages_rate = rs->num_dirty_pages_period * 1000
> +                / (end_time - rs->time_last_bitmap_sync);
> +
> +    if (!iter_count) {
> +        return;
> +    }
> +
> +    if (migrate_use_xbzrle()) {
> +        xbzrle_counters.cache_miss_rate = (double)(xbzrle_counters.cache_miss -
> +            rs->xbzrle_cache_miss_prev) / iter_count;
> +        rs->xbzrle_cache_miss_prev = xbzrle_counters.cache_miss;
> +    }
> +}
> +
>  static void migration_bitmap_sync(RAMState *rs)
>  {
>      RAMBlock *block;
> @@ -1159,9 +1178,6 @@ static void migration_bitmap_sync(RAMState *rs)
>  
>      /* more than 1 second = 1000 millisecons */
>      if (end_time > rs->time_last_bitmap_sync + 1000) {
> -        /* calculate period counters */
> -        ram_counters.dirty_pages_rate = rs->num_dirty_pages_period * 1000
> -            / (end_time - rs->time_last_bitmap_sync);
>          bytes_xfer_now = ram_counters.transferred;
>  
>          /* During block migration the auto-converge logic incorrectly detects
> @@ -1183,16 +1199,9 @@ static void migration_bitmap_sync(RAMState *rs)
>              }
>          }
>  
> -        if (migrate_use_xbzrle()) {
> -            if (rs->iterations_prev != rs->iterations) {
> -                xbzrle_counters.cache_miss_rate =
> -                   (double)(xbzrle_counters.cache_miss -
> -                            rs->xbzrle_cache_miss_prev) /
> -                   (rs->iterations - rs->iterations_prev);
> -                rs->xbzrle_cache_miss_prev = xbzrle_counters.cache_miss;
> -            }
> -            rs->iterations_prev = rs->iterations;
> -        }
> +        migration_update_rates(rs, end_time);
> +
> +        rs->iterations_prev = rs->iterations;
>  
>          /* reset period counters */
>          rs->time_last_bitmap_sync = end_time;
> -- 
> 2.14.4
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK