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

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Date:   Mon, 9 Apr 2018 14:11:19 -0700
From:   Jonathan Helman <jonathan.helman@...cle.com>
To:     Jason Wang <jasowang@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>
Cc:     virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, virtio-dev@...ts.oasis-open.org,
        Mihai Carabas <mihai.carabas@...cle.com>
Subject: Re: [virtio-dev] Re: [PATCH v2] virtio_balloon: export hugetlb page
 allocation counts



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@...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 ...
>>
> 
> 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