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

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