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

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