Re: [Qemu-devel] [PATCH v5 09/10] migration: optimize xbzrle by reducing data copy

[Dr. David Alan Gilbert]

* address@hidden (address@hidden) wrote:
> From: ChenLiang <address@hidden>
> 
> Reducing data copy can reduce cpu overhead.
> 
> Signed-off-by: ChenLiang <address@hidden>
> Signed-off-by: Gonglei <address@hidden>

Yes, with the previous patches that's now correct.

Reviewed-by: Dr. David Alan Gilbert <address@hidden>

> ---
>  arch_init.c | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/arch_init.c b/arch_init.c
> index 84a4bd3..94b62e2 100644
> --- a/arch_init.c
> +++ b/arch_init.c
> @@ -373,11 +373,8 @@ static int save_xbzrle_page(QEMUFile *f, uint8_t 
> **current_data,
>  
>      prev_cached_page = get_cached_data(XBZRLE.cache, current_addr);
>  
> -    /* save current buffer into memory */
> -    memcpy(XBZRLE.current_buf, *current_data, TARGET_PAGE_SIZE);
> -
>      /* XBZRLE encoding (if there is no overflow) */
> -    encoded_len = xbzrle_encode_buffer(prev_cached_page, XBZRLE.current_buf,
> +    encoded_len = xbzrle_encode_buffer(prev_cached_page, *current_data,
>                                         TARGET_PAGE_SIZE, XBZRLE.encoded_buf,
>                                         TARGET_PAGE_SIZE);
>      if (encoded_len == 0) {
> @@ -396,7 +393,8 @@ static int save_xbzrle_page(QEMUFile *f, uint8_t 
> **current_data,
>  
>      /* we need to update the data in the cache, in order to get the same 
> data */
>      if (!last_stage) {
> -        memcpy(prev_cached_page, XBZRLE.current_buf, TARGET_PAGE_SIZE);
> +        xbzrle_decode_buffer(XBZRLE.encoded_buf, encoded_len, 
> prev_cached_page,
> +                             TARGET_PAGE_SIZE);
>      }
>  
>      /* Send XBZRLE based compressed page */
> -- 
> 1.7.12.4
> 
> 
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK