Re: [PATCH 2/2] blkback: Add default policy values for I/O QoS code

[Jeremy Fitzhardinge <jeremy@goop.org>]

William Pitcock wrote:
> This patch adds default values which define a default QoS policy for
> guest I/O. A sysctl interface will be added once /proc/sys/xen is available
> again... unless I come up with a better idea in the meantime.
>   

What would that interface look like?  Would the parameters be per 
domain, or per device?  Would sysfs be suitable?

    J
> Ideas?
>
> Signed-off-by: William Pitcock <nenolod@dereferenced.org>
> ---
>  drivers/xen/blkback/interface.c |    9 +++++++++
>  1 files changed, 9 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/xen/blkback/interface.c b/drivers/xen/blkback/interface.c
> index c6c3e14..9541ec4 100644
> --- a/drivers/xen/blkback/interface.c
> +++ b/drivers/xen/blkback/interface.c
> @@ -34,9 +34,13 @@
>  #include <xen/events.h>
>  #include <xen/grant_table.h>
>  #include <linux/kthread.h>
> +#include <linux/sysctl.h>
>  
>  static struct kmem_cache *blkif_cachep;
>  
> +static int blkif_reqmax = 500000;
> +static int blkif_reqrate = 512;
> +
>  blkif_t *blkif_alloc(domid_t domid)
>  {
>  	blkif_t *blkif;
> @@ -53,6 +57,11 @@ blkif_t *blkif_alloc(domid_t domid)
>  	blkif->st_print = jiffies;
>  	init_waitqueue_head(&blkif->waiting_to_free);
>  
> +	/* initialize QoS values to defaults */
> +	blkif->reqrate = blkif_reqrate;
> +	blkif->reqmax = blkif_reqmax;
> +	blkif->reqcount = blkif->reqmax;
> +
>  	return blkif;
>  }
>  
>