Re: [Qemu-devel] [RFC] Buffers/caches in VirtIO Balloon driver stats

[Wei Wang <wei.w.wang@intel.com>]

On 08/29/2017 05:57 PM, Stefan Hajnoczi wrote:
> On Sun, Aug 27, 2017 at 11:30:33PM +0200, Tomáš Golembiovský wrote:
>> Hi,
> I have CCed the relevant mailing lists and people most recently involved
> in virtio-balloon discussions.  Hopefully this will help get the right
> people to see your questions.
>
>> We'd like to include information about reclaimable memory into the
>> statistics in VirtiO Balloon driver. Namely, we'd like to include
>> counters for bufferes and caches of Linux kernel. The patch itself is
>> pretty trivial -- no problem there. But before we do that I'd like to
>> get some input from the QEMU community.
>>
>> 1) Is there any reason not to have the stats there?

Could you please share the usages of reclaimable memory via the stats?


>>
>> 2) Considering the balloon device is multiplatform (Linux, BSD,
>> Windows), is there a problem with including buffers/caches? These seem
>> to be specific to the Linux virtual memory subsystem. Of course, other
>> OSes could just report zeros. Are there some internal stats on those
>> OSes that could be filled in? I don't now if such or similar statistic
>> are available on BSD. On Windows only SystemCache stat looks like
>> something relevant. Anyone familiar with those OSes has any suggestions?
>>
>>     

One of the solutions that I'm thinking about is to make virtio 
platform-ware.

That is, the device by default supports
VIRTIO_F_LINUX,
VIRTIO_F_WINDOWS,
VIRTIO_F_BSD.

For the Linux driver, only VIRTIO_F_LINUX is supported, then we can
have Linux specific driver implementations under that feature.


Best,
Wei