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