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

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Date:   Fri, 13 Apr 2018 10:10:57 -0700
From:   Jonathan Helman <jonathan.helman@...cle.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...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 04/13/2018 06:44 AM, Michael S. Tsirkin wrote:
> On Fri, Apr 13, 2018 at 03:01:11PM +0800, Jason Wang wrote:
>>
>>
>> On 2018年04月12日 08:24, Jonathan Helman wrote:
>>>
>>>
>>> On 04/10/2018 08:12 PM, Jason Wang wrote:
>>>>
>>>>
>>>> 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?
>>>
>>> Yes, this testing scenario looks good. Thanks.
>>>
>>> Jon
>>
>> Hi Jon:
>>
>> I mean e.g compiling qemu with new linux headers. E.g current qemu has:
>>
>> static const char *balloon_stat_names[] = {
>>     [VIRTIO_BALLOON_S_SWAP_IN] = "stat-swap-in",
>>     [VIRTIO_BALLOON_S_SWAP_OUT] = "stat-swap-out",
>>     [VIRTIO_BALLOON_S_MAJFLT] = "stat-major-faults",
>>     [VIRTIO_BALLOON_S_MINFLT] = "stat-minor-faults",
>>     [VIRTIO_BALLOON_S_MEMFREE] = "stat-free-memory",
>>     [VIRTIO_BALLOON_S_MEMTOT] = "stat-total-memory",
>>     [VIRTIO_BALLOON_S_AVAIL] = "stat-available-memory",
>>     [VIRTIO_BALLOON_S_CACHES] = "stat-disk-caches",
>>     [VIRTIO_BALLOON_S_NR] = NULL
>> };
>>
>> I'm afraid it will be broken if VIRTIO_BALLOON_S_NR is 10.
>>
>> Thanks
> 
> Well it is handy for sizing arrays and this isn't the first time we did
> this:
> 
> commit 4d32029b8ddb7be4d1699c6d8e1675ff5476d149
> Author: Tomáš Golembiovský <tgolembi@...hat.com>
> Date:   Sun Nov 12 13:05:38 2017 +0100
> 
>      virtio_balloon: include disk/file caches memory statistics
>      
>    
> 
> commit 5057dcd0f1aaad57e07e728ba20a99e205c6b9de
> Author: Igor Redko <redkoi@...tuozzo.com>
> Date:   Thu Mar 17 14:19:08 2016 -0700
> 
>      virtio_balloon: export 'available' memory to balloon statistics
>      
> 
> how about we give QEMU a hand and just put the list of names in
> the header?
> 
> I posted a patch like that, pls review.
> 

Sorry, maybe I'm missing something. We have an internal copy of the 
header file in qemu under 
include/standard-headers/linux/virtio_balloon.h, which 
hw/virtio/virtio-balloon.c includes (through including 
hw/virtio/virtio-balloon.h). I thought qemu would use internal header 
files so that it could be compiled on any Linux kernel version. So when 
would we ever have the issue Jason is discussing?

Thanks,
Jon