Re: [Qemu-devel] [PATCH v5] block: Introduce "null" drivers

[Kevin Wolf <kwolf@redhat.com>]

Am 01.09.2014 um 11:22 hat Fam Zheng geschrieben:
> This is an analogue to Linux null_blk. It can be used for testing or
> benchmarking block device emulation and general block layer
> functionalities such as coroutines and throttling, where disk IO is not
> necessary or wanted.
> 
> Use null-aio:// for AIO version, and null-co:// for coroutine version.
> 
> Signed-off-by: Fam Zheng <famz@redhat.com>
> Reviewed-by: Benoît Canet <benoit.canet@nodalink.com>

> +static BlockDriver bdrv_null_co = {
> +    .format_name            = "null-co",
> +    .protocol_name          = "null-co",
> +    .instance_size          = sizeof(BDRVNullState),
> +
> +    .bdrv_file_open         = null_file_open,
> +    .bdrv_close             = null_close,
> +    .bdrv_getlength         = null_getlength,
> +
> +    .bdrv_read              = null_co_read,
> +    .bdrv_write             = null_co_write,

Any reason not to use the native .bdrv_co_readv/writev interfaces
instead of the old, emulated versions that involve a bounce buffer?

> +    .bdrv_co_flush_to_disk  = null_co_flush,
> +};

Kevin