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

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2009-03-31 at 03:22 -0400, Jeremy Fitzhardinge wrote:
> 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?

The netback interface to the similar thing is via xenstore, FWIW.

Ian.

> 
>     J
> > Ideas?
> >
> > Signed-off-by: William Pitcock <nenolod@xxxxxxxxxxxxxxxx>
> > ---
> >  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;
> >  }
> >  
> >   
> 
> 
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