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

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Date:   Wed, 11 Apr 2018 11:12:04 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Jonathan Helman <jonathan.helman@...cle.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 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@...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

Hi Jon:

Have you tested new driver with old qemu?

Thanks