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

[Jason Wang <jasowang@redhat.com>]

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

>
>> Thanks
>
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