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

["Tomáš Golembiovský" <tgolembi@redhat.com>]

Resending. It did not reach virtio-dev the first time.

On Tue, 12 Sep 2017 16:29:47 +0200
Tomáš Golembiovský <tgolembi@redhat.com> wrote:

> On Tue, 29 Aug 2017 20:01:53 +0800
> Wei Wang <wei.w.wang@intel.com> wrote:
> 
> > 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?
> 
> I'll go ahead then and start sending patches. What would be the proper
> course of action here? Send patch for the driver first, or send patch
> for QEMU first or send both patches right away?
> 
> 
> > >>
> > >> 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.
> 
> This is not necessary. IIUC the driver does not need to send all the
> stats. We can simply treat those stats as specific to Linux driver and
> other drivers will not send them. Then QEMU will treat them as if zero
> was reported.
> 
> > 
> > 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.
> 
> 
> Since there were no suggestions for similar stats on other OSes I'd say
> we treat the stats for buffers and caches as Linux specific. If there is
> any need to send similar stats for other OSes we will add new stat fields
> (specific for that particular OS).
> 
> 
> Thanks,
> 
>     Tomas
> 
> -- 
> Tomáš Golembiovský <tgolembi@redhat.com>


-- 
Tomáš Golembiovský <tgolembi@redhat.com>