linux-kernel - Re: [virtio-dev] Re: [PATCH v2] virtio_balloon: export hugetlb page allocation counts

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Date:   Thu, 22 Mar 2018 05:10:09 +0200
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     Jonathan Helman <jonathan.helman@...cle.com>,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, virtio-dev@...ts.oasis-open.org
Subject: Re: [virtio-dev] Re: [PATCH v2] virtio_balloon: export hugetlb page
 allocation counts

On Thu, Mar 22, 2018 at 09:52:18AM +0800, Jason Wang wrote:
> 
> 
> On 2018年03月20日 12:26, Jonathan Helman wrote:
> > > On Mar 19, 2018, at 7:31 PM, Jason Wang <jasowang@...hat.com> wrote:
> > > 
> > > 
> > > 
> > > On 2018年03月20日 06:14, Jonathan Helman wrote:
> > > > Export the number of successful and failed hugetlb page
> > > > allocations via the virtio balloon driver. These 2 counts
> > > > come directly from the vm_events HTLB_BUDDY_PGALLOC and
> > > > HTLB_BUDDY_PGALLOC_FAIL.
> > > > 
> > > > Signed-off-by: Jonathan Helman <jonathan.helman@...cle.com>
> > > Reviewed-by: Jason Wang <jasowang@...hat.com>
> > Thanks.
> > 
> > > > ---
> > > >   drivers/virtio/virtio_balloon.c     | 6 ++++++
> > > >   include/uapi/linux/virtio_balloon.h | 4 +++-
> > > >   2 files changed, 9 insertions(+), 1 deletion(-)
> > > > 
> > > > diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
> > > > index dfe5684..6b237e3 100644
> > > > --- a/drivers/virtio/virtio_balloon.c
> > > > +++ b/drivers/virtio/virtio_balloon.c
> > > > @@ -272,6 +272,12 @@ static unsigned int update_balloon_stats(struct virtio_balloon *vb)
> > > >   				pages_to_bytes(events[PSWPOUT]));
> > > >   	update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
> > > >   	update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
> > > > +#ifdef CONFIG_HUGETLB_PAGE
> > > > +	update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGALLOC,
> > > > +		    events[HTLB_BUDDY_PGALLOC]);
> > > > +	update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGFAIL,
> > > > +		    events[HTLB_BUDDY_PGALLOC_FAIL]);
> > > > +#endif
> > > >   #endif
> > > >   	update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
> > > >   				pages_to_bytes(i.freeram));
> > > > diff --git a/include/uapi/linux/virtio_balloon.h b/include/uapi/linux/virtio_balloon.h
> > > > index 4e8b830..40297a3 100644
> > > > --- a/include/uapi/linux/virtio_balloon.h
> > > > +++ b/include/uapi/linux/virtio_balloon.h
> > > > @@ -53,7 +53,9 @@ struct virtio_balloon_config {
> > > >   #define VIRTIO_BALLOON_S_MEMTOT   5   /* Total amount of memory */
> > > >   #define VIRTIO_BALLOON_S_AVAIL    6   /* Available memory as in /proc */
> > > >   #define VIRTIO_BALLOON_S_CACHES   7   /* Disk caches */
> > > > -#define VIRTIO_BALLOON_S_NR       8
> > > > +#define VIRTIO_BALLOON_S_HTLB_PGALLOC  8  /* Hugetlb page allocations */
> > > > +#define VIRTIO_BALLOON_S_HTLB_PGFAIL   9  /* Hugetlb page allocation failures */
> > > > +#define VIRTIO_BALLOON_S_NR       10
> > > >     /*
> > > >    * Memory statistics structure.
> > > Not for this patch, but it looks to me that exporting such nr through uapi is fragile.
> > Sorry, can you explain what you mean here?
> > 
> > Jon
> 
> Spec said "Within an output buffer submitted to the statsq, the device MUST
> ignore entries with tag values that it does not recognize". So exporting
> VIRTIO_BALLOON_S_NR seems useless and device implementation can not depend
> on such number in uapi.
> 
> Thanks

Suggestions? I don't like to break build for people ...

> > 
> > > Thanks
> > 
> > ---------------------------------------------------------------------
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> >