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Date: Wed, 3 Sep 2014 12:10:38 +0200
From: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20140903101038.GG7717@noname.str.redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v5] block: Introduce "null" drivers
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To: Fam Zheng <famz@redhat.com>
Cc: benoit.canet@irqsave.net, qemu-devel@nongnu.org, armbru@redhat.com, Stefan Hajnoczi <stefanha@redhat.com>, pbonzini@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.
>=20
> Use null-aio:// for AIO version, and null-co:// for coroutine version.
>=20
> Signed-off-by: Fam Zheng <famz@redhat.com>
> Reviewed-by: Beno=EEt Canet <benoit.canet@nodalink.com>

> +static BlockDriver bdrv_null_co =3D {
> +    .format_name            =3D "null-co",
> +    .protocol_name          =3D "null-co",
> +    .instance_size          =3D sizeof(BDRVNullState),
> +
> +    .bdrv_file_open         =3D null_file_open,
> +    .bdrv_close             =3D null_close,
> +    .bdrv_getlength         =3D null_getlength,
> +
> +    .bdrv_read              =3D null_co_read,
> +    .bdrv_write             =3D 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  =3D null_co_flush,
> +};

Kevin