Re: [Xen-devel] [PATCH v4 2/2] xen/block: add multi-page ring support

[Julien Grall <julien.grall@citrix.com>]

Hi,

On 20/05/15 14:10, Bob Liu wrote:
> ---
>  drivers/block/xen-blkback/blkback.c |  12 ++++
>  drivers/block/xen-blkback/common.h  |   3 +-
>  drivers/block/xen-blkback/xenbus.c  |  85 +++++++++++++++++++++-------
>  drivers/block/xen-blkfront.c        | 110 ++++++++++++++++++++++++++----------
>  4 files changed, 161 insertions(+), 49 deletions(-)
> 
> diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
> index 713fc9f..057890f 100644
> --- a/drivers/block/xen-blkback/blkback.c
> +++ b/drivers/block/xen-blkback/blkback.c
> @@ -84,6 +84,12 @@ MODULE_PARM_DESC(max_persistent_grants,
>                   "Maximum number of grants to map persistently");
>  
>  /*
> + * Maximum number of pages to be used as the ring between front and backend
> + */
> +unsigned int xen_blkif_max_ring_order = XENBUS_MAX_RING_PAGE_ORDER;

We will soon support 64KB page granularity with ARM64, although the PV
protocol will keep a 4KB page granularity.

Can you clarify with granularity is used here? The one of the host or
the one of the PV protocol?

> +module_param_named(max_ring_page_order, xen_blkif_max_ring_order, int, S_IRUGO);
> +MODULE_PARM_DESC(max_ring_page_order, "Maximum order of pages to be used as the ring");
> +/*
>   * The LRU mechanism to clean the lists of persistent grants needs to
>   * be executed periodically. The time interval between consecutive executions
>   * of the purge mechanism is set in ms.

Regards,

-- 
Julien Grall