Re: [PATCH 9/9] migration/ram: calculate un/encoded_size only when needed.

[Dr. David Alan Gilbert]

* Mao Zhongyi (maozhongyi@cmss.chinamobile.com) wrote:
> Signed-off-by: Mao Zhongyi <maozhongyi@cmss.chinamobile.com>
> ---
>  migration/ram.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/migration/ram.c b/migration/ram.c
> index 41cc530d9d..ca20030b64 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -910,14 +910,15 @@ static void migration_update_rates(RAMState *rs, 
> int64_t end_time)
>          xbzrle_counters.cache_miss_rate = 
> (double)(xbzrle_counters.cache_miss -
>              rs->xbzrle_cache_miss_prev) / page_count;
>          rs->xbzrle_cache_miss_prev = xbzrle_counters.cache_miss;
> -        unencoded_size = (xbzrle_counters.pages - rs->xbzrle_pages_prev) *
> -                         TARGET_PAGE_SIZE;
> -        encoded_size = xbzrle_counters.bytes - rs->xbzrle_bytes_prev;
>          if (xbzrle_counters.pages == rs->xbzrle_pages_prev) {
>              xbzrle_counters.encoding_rate = 0;
> -        } else if (!encoded_size) {
> +        } else if (xbzrle_counters.bytes == rs->xbzrle_bytes_prev) {

No, I don't think this change is worth it - this is really just the same
as 'encoded_size', and then we may as well keep the two together.

Dave

>              xbzrle_counters.encoding_rate = UINT64_MAX;
>          } else {
> +            unencoded_size = (xbzrle_counters.pages - rs->xbzrle_pages_prev) 
> *
> +                             TARGET_PAGE_SIZE;
> +            encoded_size = xbzrle_counters.bytes - rs->xbzrle_bytes_prev;
> +
>              xbzrle_counters.encoding_rate = unencoded_size / encoded_size;
>          }
>          rs->xbzrle_pages_prev = xbzrle_counters.pages;
> -- 
> 2.17.1
> 
> 
> 
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK