Re: [Qemu-trivial] [PATCH] arch_init.c: remove duplicate function

[Laszlo Ersek <lersek@redhat.com>]

On 04/14/14 04:27, Amos Kong wrote:
> We already have a function buffer_is_zero() in util/cutils.c
> 
> Signed-off-by: Amos Kong <akong@redhat.com>
> ---
>  arch_init.c | 9 ++-------
>  1 file changed, 2 insertions(+), 7 deletions(-)
> 
> diff --git a/arch_init.c b/arch_init.c
> index 60c975d..342e5dc 100644
> --- a/arch_init.c
> +++ b/arch_init.c
> @@ -152,11 +152,6 @@ int qemu_read_default_config_files(bool userconfig)
>      return 0;
>  }
>  
> -static inline bool is_zero_range(uint8_t *p, uint64_t size)
> -{
> -    return buffer_find_nonzero_offset(p, size) == size;
> -}
> -
>  /* struct contains XBZRLE cache and a static page
>     used by the compression */
>  static struct {
> @@ -587,7 +582,7 @@ static int ram_save_block(QEMUFile *f, bool last_stage)
>                          acct_info.dup_pages++;
>                      }
>                  }
> -            } else if (is_zero_range(p, TARGET_PAGE_SIZE)) {
> +            } else if (buffer_is_zero(p, TARGET_PAGE_SIZE)) {
>                  acct_info.dup_pages++;
>                  bytes_sent = save_block_hdr(f, block, offset, cont,
>                                              RAM_SAVE_FLAG_COMPRESS);
> @@ -983,7 +978,7 @@ static inline void *host_from_stream_offset(QEMUFile *f,
>   */
>  void ram_handle_compressed(void *host, uint8_t ch, uint64_t size)
>  {
> -    if (ch != 0 || !is_zero_range(host, size)) {
> +    if (ch != 0 || !buffer_is_zero(host, size)) {
>          memset(host, ch, size);
>      }
>  }
> 

This seems to be correct, functionally -- apparently buffer_is_zero()
has laxer size requirements than buffer_find_nonzero_offset(). However,
I think the latter might be faster.

For ram_save_block() I guess the difference is negligible. But
ram_handle_compressed() is also called from "migration-rdma.c", where I
can't even guess if a little bit of slowdown would count.

I'm OK with the patch if Michael (CC'd) is.

Thanks
Laszlo