Re: [Qemu-devel] [RFC 10/12] Add qemu_put_buffer_no_copy

["Michael R. Hines" <mrhines@linux.vnet.ibm.com>]

Can you add a "flag" or something to indicate that the iov pointer 
belongs to RAM and not to device state?

That way, I could re-use this code for RDMA - if I see this flag, I will 
know to send to RDMA.....

- Michael


On 03/21/2013 05:09 AM, Orit Wasserman wrote:
> This allow us to add a buffer to the iovec to send without copying it
> into the static buffer.
>
> Signed-off-by: Orit Wasserman <owasserm@redhat.com>
> ---
>   include/migration/qemu-file.h |  5 +++++
>   savevm.c                      | 42 ++++++++++++++++++++++++------------------
>   2 files changed, 29 insertions(+), 18 deletions(-)
>
> diff --git a/include/migration/qemu-file.h b/include/migration/qemu-file.h
> index 8d3da9b..5168be2 100644
> --- a/include/migration/qemu-file.h
> +++ b/include/migration/qemu-file.h
> @@ -75,6 +75,11 @@ int qemu_fclose(QEMUFile *f);
>   int64_t qemu_ftell(QEMUFile *f);
>   void qemu_put_buffer(QEMUFile *f, const uint8_t *buf, int size);
>   void qemu_put_byte(QEMUFile *f, int v);
> +/*
> + * put_buffer without copying the buffer.
> + * The buffer should be available till it is sent.
> + */
> +void qemu_put_buffer_no_copy(QEMUFile *f, const uint8_t *buf, int size);
>
>   static inline void qemu_put_ubyte(QEMUFile *f, unsigned int v)
>   {
> diff --git a/savevm.c b/savevm.c
> index 40d96f4..32a506e 100644
> --- a/savevm.c
> +++ b/savevm.c
> @@ -629,6 +629,22 @@ void qemu_put_buffer(QEMUFile *f, const uint8_t *buf, int size)
>   {
>       int l;
>
> +    while (size > 0) {
> +        l = IO_BUF_SIZE - f->buf_index;
> +        if (l > size) {
> +            l = size;
> +        }
> +        memcpy(f->buf + f->buf_index, buf, l);
> +        f->buf_index += l;
> +        f->is_write = 1;
> +        qemu_put_buffer_no_copy(f, f->buf + (f->buf_index - l), l);
> +        buf += l;
> +        size -= l;
> +    }
> +}
> +
> +void qemu_put_buffer_no_copy(QEMUFile *f, const uint8_t *buf, int size)
> +{
>       if (f->last_error) {
>           return;
>       }
> @@ -639,24 +655,14 @@ void qemu_put_buffer(QEMUFile *f, const uint8_t *buf, int size)
>           abort();
>       }
>
> -    while (size > 0) {
> -        l = IO_BUF_SIZE - f->buf_index;
> -        if (l > size)
> -            l = size;
> -        memcpy(f->buf + f->buf_index, buf, l);
> -        f->iov[f->iovcnt].iov_base = f->buf + f->buf_index;
> -        f->iov[f->iovcnt++].iov_len = l;
> -        f->is_write = 1;
> -        f->buf_index += l;
> -        f->bytes_xfer += l;
> -        buf += l;
> -        size -= l;
> -        if (f->buf_index >= IO_BUF_SIZE || f->iovcnt >= MAX_IOV_SIZE) {
> -            qemu_fflush(f);
> -            if (qemu_file_get_error(f)) {
> -                break;
> -            }
> -        }
> +    f->iov[f->iovcnt].iov_base = (uint8_t *)buf;
> +    f->iov[f->iovcnt++].iov_len = size;
> +
> +    f->is_write = 1;
> +    f->bytes_xfer += size;
> +
> +    if (f->buf_index >= IO_BUF_SIZE || f->iovcnt >= MAX_IOV_SIZE) {
> +        qemu_fflush(f);
>       }
>   }
>