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

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Apr 13, 2018 at 03:01:11PM +0800, Jason Wang wrote:
> 
> 
> On 2018年04月12日 08:24, Jonathan Helman wrote:
> > 
> > 
> > On 04/10/2018 08:12 PM, Jason Wang wrote:
> > > 
> > > 
> > > On 2018年04月10日 05:11, Jonathan Helman wrote:
> > > > 
> > > > 
> > > > On 03/22/2018 07:38 PM, Jason Wang wrote:
> > > > > 
> > > > > 
> > > > > On 2018年03月22日 11:10, Michael S. Tsirkin wrote:
> > > > > > 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@redhat.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@oracle.com>
> > > > > > > > > Reviewed-by: Jason Wang<jasowang@redhat.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 ...
> > > > > > 
> > > > > 
> > > > > Didn't have a good idea. But maybe we should keep
> > > > > VIRTIO_BALLOON_S_NR unchanged, and add a comment here.
> > > > > 
> > > > > Thanks
> > > > 
> > > > I think Jason's comment is for a future patch. Didn't see this
> > > > patch get applied, so wondering if it could be.
> > > > 
> > > > Thanks,
> > > > Jon
> > > 
> > > Hi Jon:
> > > 
> > > Have you tested new driver with old qemu?
> > 
> > Yes, this testing scenario looks good. Thanks.
> > 
> > Jon
> 
> Hi Jon:
> 
> I mean e.g compiling qemu with new linux headers. E.g current qemu has:
> 
> static const char *balloon_stat_names[] = {
>    [VIRTIO_BALLOON_S_SWAP_IN] = "stat-swap-in",
>    [VIRTIO_BALLOON_S_SWAP_OUT] = "stat-swap-out",
>    [VIRTIO_BALLOON_S_MAJFLT] = "stat-major-faults",
>    [VIRTIO_BALLOON_S_MINFLT] = "stat-minor-faults",
>    [VIRTIO_BALLOON_S_MEMFREE] = "stat-free-memory",
>    [VIRTIO_BALLOON_S_MEMTOT] = "stat-total-memory",
>    [VIRTIO_BALLOON_S_AVAIL] = "stat-available-memory",
>    [VIRTIO_BALLOON_S_CACHES] = "stat-disk-caches",
>    [VIRTIO_BALLOON_S_NR] = NULL
> };
> 
> I'm afraid it will be broken if VIRTIO_BALLOON_S_NR is 10.
> 
> Thanks

Well it is handy for sizing arrays and this isn't the first time we did
this:

commit 4d32029b8ddb7be4d1699c6d8e1675ff5476d149
Author: Tomáš Golembiovský <tgolembi@redhat.com>
Date:   Sun Nov 12 13:05:38 2017 +0100

    virtio_balloon: include disk/file caches memory statistics
    
  

commit 5057dcd0f1aaad57e07e728ba20a99e205c6b9de
Author: Igor Redko <redkoi@virtuozzo.com>
Date:   Thu Mar 17 14:19:08 2016 -0700

    virtio_balloon: export 'available' memory to balloon statistics
    

how about we give QEMU a hand and just put the list of names in
the header?

I posted a patch like that, pls review.

-- 
MST