Linux Virtualization - Jan 2017 - [virtio-dev] Re: [PATCH v6 kernel 2/5] virtio-balloon: define new feature bit and head struct

On Wed, Dec 21, 2016 at 02:52:25PM +0800, Liang Li
wrote:
> Add a new feature which supports sending the page information
> with range array. The current implementation uses PFNs array,
> which is not very efficient. Using ranges can improve the
> performance of inflating/deflating significantly.
> 
> Signed-off-by: Liang Li <liang.z.li at intel.com>
> Cc: Michael S. Tsirkin <mst at redhat.com>
> Cc: Paolo Bonzini <pbonzini at redhat.com>
> Cc: Cornelia Huck <cornelia.huck at de.ibm.com>
> Cc: Amit Shah <amit.shah at redhat.com>
> Cc: Dave Hansen <dave.hansen at intel.com>
> Cc: Andrea Arcangeli <aarcange at redhat.com>
> Cc: David Hildenbrand <david at redhat.com>
> ---
>  include/uapi/linux/virtio_balloon.h | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/include/uapi/linux/virtio_balloon.h
b/include/uapi/linux/virtio_balloon.h
> index 343d7dd..2f850bf 100644
> --- a/include/uapi/linux/virtio_balloon.h
> +++ b/include/uapi/linux/virtio_balloon.h
> @@ -34,10 +34,14 @@
>  #define VIRTIO_BALLOON_F_MUST_TELL_HOST	0 /* Tell before reclaiming pages
*/
>  #define VIRTIO_BALLOON_F_STATS_VQ	1 /* Memory Stats virtqueue */
>  #define VIRTIO_BALLOON_F_DEFLATE_ON_OOM	2 /* Deflate balloon on OOM */
> +#define VIRTIO_BALLOON_F_PAGE_RANGE	3 /* Send page info with ranges */
>  
>  /* Size of a PFN in the balloon interface. */
>  #define VIRTIO_BALLOON_PFN_SHIFT 12
>  
> +/* Bits width for the length of the pfn range */
What does this mean? Couldn't figure it out.
> +#define VIRTIO_BALLOON_NR_PFN_BITS 12
> +
>  struct virtio_balloon_config {
>  	/* Number of pages host wants Guest to give up. */
>  	__u32 num_pages;
> @@ -82,4 +86,12 @@ struct virtio_balloon_stat {
>  	__virtio64 val;
>  } __attribute__((packed));
>  
> +/* Response header structure */
> +struct virtio_balloon_resp_hdr {
> +	__le64 cmd : 8; /* Distinguish different requests type */
> +	__le64 flag: 8; /* Mark status for a specific request type */
> +	__le64 id : 16; /* Distinguish requests of a specific type */
> +	__le64 data_len: 32; /* Length of the following data, in bytes */
This use of __le64 makes no sense.  Just use u8/le16/le32 pls.
> +};
> +
>  #endif /* _LINUX_VIRTIO_BALLOON_H */
> -- 
> 1.9.1

> On Wed, Dec 21, 2016 at 02:52:25PM +0800, Liang Li wrote:
> > Add a new feature which supports sending the page information with
> > range array. The current implementation uses PFNs array, which is not
> > very efficient. Using ranges can improve the performance of
> > inflating/deflating significantly.
> >
> > Signed-off-by: Liang Li <liang.z.li at intel.com>
> > Cc: Michael S. Tsirkin <mst at redhat.com>
> > Cc: Paolo Bonzini <pbonzini at redhat.com>
> > Cc: Cornelia Huck <cornelia.huck at de.ibm.com>
> > Cc: Amit Shah <amit.shah at redhat.com>
> > Cc: Dave Hansen <dave.hansen at intel.com>
> > Cc: Andrea Arcangeli <aarcange at redhat.com>
> > Cc: David Hildenbrand <david at redhat.com>
> > ---
> >  include/uapi/linux/virtio_balloon.h | 12 ++++++++++++
> >  1 file changed, 12 insertions(+)
> >
> > diff --git a/include/uapi/linux/virtio_balloon.h
> > b/include/uapi/linux/virtio_balloon.h
> > index 343d7dd..2f850bf 100644
> > --- a/include/uapi/linux/virtio_balloon.h
> > +++ b/include/uapi/linux/virtio_balloon.h
> > @@ -34,10 +34,14 @@
> >  #define VIRTIO_BALLOON_F_MUST_TELL_HOST	0 /* Tell before
> reclaiming pages */
> >  #define VIRTIO_BALLOON_F_STATS_VQ	1 /* Memory Stats virtqueue
> */
> >  #define VIRTIO_BALLOON_F_DEFLATE_ON_OOM	2 /* Deflate balloon
> on OOM */
> > +#define VIRTIO_BALLOON_F_PAGE_RANGE	3 /* Send page info
> with ranges */
> >
> >  /* Size of a PFN in the balloon interface. */  #define
> > VIRTIO_BALLOON_PFN_SHIFT 12
> >
> > +/* Bits width for the length of the pfn range */
> 
> What does this mean? Couldn't figure it out.
> 
> > +#define VIRTIO_BALLOON_NR_PFN_BITS 12
> > +
> >  struct virtio_balloon_config {
> >  	/* Number of pages host wants Guest to give up. */
> >  	__u32 num_pages;
> > @@ -82,4 +86,12 @@ struct virtio_balloon_stat {
> >  	__virtio64 val;
> >  } __attribute__((packed));
> >
> > +/* Response header structure */
> > +struct virtio_balloon_resp_hdr {
> > +	__le64 cmd : 8; /* Distinguish different requests type */
> > +	__le64 flag: 8; /* Mark status for a specific request type */
> > +	__le64 id : 16; /* Distinguish requests of a specific type */
> > +	__le64 data_len: 32; /* Length of the following data, in bytes */
> 
> This use of __le64 makes no sense.  Just use u8/le16/le32 pls.
> 
Got it, will change in the next version. 

And could help take a look at other parts? as well as the QEMU part.

Thanks!
Liang

On Fri, Jan 13, 2017 at 09:24:22AM +0000, Li, Liang Z
wrote:
> > On Wed, Dec 21, 2016 at 02:52:25PM +0800, Liang Li wrote:
> > > Add a new feature which supports sending the page information
with
> > > range array. The current implementation uses PFNs array, which is
not
> > > very efficient. Using ranges can improve the performance of
> > > inflating/deflating significantly.
> > >
> > > Signed-off-by: Liang Li <liang.z.li at intel.com>
> > > Cc: Michael S. Tsirkin <mst at redhat.com>
> > > Cc: Paolo Bonzini <pbonzini at redhat.com>
> > > Cc: Cornelia Huck <cornelia.huck at de.ibm.com>
> > > Cc: Amit Shah <amit.shah at redhat.com>
> > > Cc: Dave Hansen <dave.hansen at intel.com>
> > > Cc: Andrea Arcangeli <aarcange at redhat.com>
> > > Cc: David Hildenbrand <david at redhat.com>
> > > ---
> > >  include/uapi/linux/virtio_balloon.h | 12 ++++++++++++
> > >  1 file changed, 12 insertions(+)
> > >
> > > diff --git a/include/uapi/linux/virtio_balloon.h
> > > b/include/uapi/linux/virtio_balloon.h
> > > index 343d7dd..2f850bf 100644
> > > --- a/include/uapi/linux/virtio_balloon.h
> > > +++ b/include/uapi/linux/virtio_balloon.h
> > > @@ -34,10 +34,14 @@
> > >  #define VIRTIO_BALLOON_F_MUST_TELL_HOST	0 /* Tell before
> > reclaiming pages */
> > >  #define VIRTIO_BALLOON_F_STATS_VQ	1 /* Memory Stats virtqueue
> > */
> > >  #define VIRTIO_BALLOON_F_DEFLATE_ON_OOM	2 /* Deflate balloon
> > on OOM */
> > > +#define VIRTIO_BALLOON_F_PAGE_RANGE	3 /* Send page info
> > with ranges */
> > >
> > >  /* Size of a PFN in the balloon interface. */  #define
> > > VIRTIO_BALLOON_PFN_SHIFT 12
> > >
> > > +/* Bits width for the length of the pfn range */
> > 
> > What does this mean? Couldn't figure it out.
> > 
> > > +#define VIRTIO_BALLOON_NR_PFN_BITS 12
> > > +
> > >  struct virtio_balloon_config {
> > >  	/* Number of pages host wants Guest to give up. */
> > >  	__u32 num_pages;
> > > @@ -82,4 +86,12 @@ struct virtio_balloon_stat {
> > >  	__virtio64 val;
> > >  } __attribute__((packed));
> > >
> > > +/* Response header structure */
> > > +struct virtio_balloon_resp_hdr {
> > > +	__le64 cmd : 8; /* Distinguish different requests type */
> > > +	__le64 flag: 8; /* Mark status for a specific request type */
> > > +	__le64 id : 16; /* Distinguish requests of a specific type */
> > > +	__le64 data_len: 32; /* Length of the following data, in bytes
*/
> > 
> > This use of __le64 makes no sense.  Just use u8/le16/le32 pls.
> > 
> 
> Got it, will change in the next version. 
> 
> And could help take a look at other parts? as well as the QEMU part.
> 
> Thanks!
> Liang
Yes but first I would like to understand how come no fields
in this new structure come up if I search for them in the
following patch. I don't see why should I waste time on
reviewing the implementation if the interface isn't
reasonable. You don't have to waste it too - just send RFC
patches with the header until we can agree on it.

-- 
MST