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I can see it being useful. But I'd note > that the existing code has a trace function that outputs pretty much all > the same information when it is reported to the Hyper-V host in > post_status() every 1 second. However, the debugfs interface might be > a bit easier to use for ongoing sampling. Related, I see that the VMware > balloon driver use the debugfs interface, but no tracing. The virtio > balloon driver has neither. I'm not against adding this debugfs interface, > but I wanted to make sure there's real value over the existing tracing. > > See also some minor comments below. virtio efforts: https://www.spinics.net/lists/kernel/msg4425155.html In general balloon information is always reported to the host, that is why balloon is invented. Though the information inside the guest is not always available and it is hard to track/guess. We have had a lot of trouble to convince our customers that the memory was taken by host being inside virtual machine. Thus debugfs interface is good for such rare checks especially keeping in mind that this would be the same for most frequently used by us balloons. Den