Messages in this thread |  | | Date | Sun, 10 Nov 2019 05:09:13 -0500 | From | Brian Masney <> | Subject | Re: "statsfs" API design |
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On Sun, Nov 10, 2019 at 10:14:35AM +0100, Greg KH wrote: > On Sat, Nov 09, 2019 at 09:44:41PM +0300, Alexey Dobriyan wrote: > > > statsfs is a proposal for a new Linux kernel synthetic filesystem, > > > to be mounted in /sys/kernel/stats > > > > I think /proc experiment teaches pretty convincingly that dressing > > things into a filesystem can be done but ultimately is a stupid idea. > > It adds so much overhead for small-to-medium systems. > > > > > The first user of statsfs would be KVM, which is currently exposing > > > its stats in debugfs > > > > > Google has KVM patches to gather statistics in a binary format > > > > Which is a right thing to do. > > It's always "simpler" to just take binary data and suck it in. That > works for a year or so until another value needs to be supported. Or > removed. Or features are backported. > > The reason text values in individual files work is they are "self > describable" and "self discoverable". You "know" what the value is and > that it is supported because the file is there or not. With binary > values in a single file you do not know any of that. > > So you need some way of describing the data to userspace in order for > this to work properly over the next 20+ years. > > Maybe something like varlink which describes the data coming from the > kernel in an easy-to-handle format? Or something else, but just using > blobs does not work over the long-term, sorry.
What about using a text format like YAML? Here's some benefits:
- The fields are self describing based on the key name. - New fields can be easily added without breaking compatibility. - Allows for a script to easily parse the contents while keeping human readability. - Would work for systems that run busybox as their userspace without having to install additional tools. - Allows for a nested data structure.
The downside is that the output would be larger than a binary interface but it's more maintainable in my opinion.
Brian
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