Re: [Qemu-devel] [PATCH v3 8/9] Use qemu_put_buffer_no_copy for guest memory pages

[Michael S. Tsirkin]

On Thu, Mar 21, 2013 at 06:05:39PM +0200, Orit Wasserman wrote:
> This will remove an unneeded copy of guest memory pages.
> For the page header and device state we still copy the data to the
> static buffer the other option is to allocate the memory on demand
> which is more expensive.
> 
> Signed-off-by: Orit Wasserman <address@hidden>

Okay so with this, the _nocopy can be later rewritten to do vmsplice to
save another copy? Cool.

> ---
>  arch_init.c | 2 +-
>  savevm.c    | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch_init.c b/arch_init.c
> index 98e2bc6..27b53eb 100644
> --- a/arch_init.c
> +++ b/arch_init.c
> @@ -481,7 +481,7 @@ static int ram_save_block(QEMUFile *f, bool last_stage)
>              /* XBZRLE overflow or normal page */
>              if (bytes_sent == -1) {
>                  bytes_sent = save_block_hdr(f, block, offset, cont, 
> RAM_SAVE_FLAG_PAGE);
> -                qemu_put_buffer(f, p, TARGET_PAGE_SIZE);
> +                qemu_put_buffer_no_copy(f, p, TARGET_PAGE_SIZE);
>                  bytes_sent += TARGET_PAGE_SIZE;
>                  acct_info.norm_pages++;
>              }
> diff --git a/savevm.c b/savevm.c
> index fbfb9e3..50e8fb2 100644
> --- a/savevm.c
> +++ b/savevm.c
> @@ -634,7 +634,7 @@ void qemu_put_buffer_no_copy(QEMUFile *f, const uint8_t 
> *buf, int size)
>          abort();
>      }
>  
> -    f->iov[f->iovcnt].iov_base = f->buf + f->buf_index;
> +    f->iov[f->iovcnt].iov_base = (uint8_t *)buf;
>      f->iov[f->iovcnt++].iov_len = size;
>  
>      f->is_write = 1;
> -- 
> 1.7.11.7