Comment by Rochus
9 days ago
The HongMeng kernel, performance wise, seems indeed to be in the same ballpark as sel4 or QNX, but it doesn't seem that it will be open-sourced.
9 days ago
The HongMeng kernel, performance wise, seems indeed to be in the same ballpark as sel4 or QNX, but it doesn't seem that it will be open-sourced.
Perhaps it won't be open sourced, but having read one of the papers written for it, the principles behind its advancements can easily be added to the microkernel repertoire.
What's the core concept compared to other kernels?
At its core, it's not too distinct from, say, seL4, but some of the distinctions are useful. I think Hongmeng's work on isolation classes (particularly in transferring components across classes), a performance-motivated partial alternative to capabilities, OS service coalescing and partitioning, and porting Linux drivers are valuable (see sections 4.2-4.4 and 5 [0]). It's not that these changes should be accepted wholesale, but I think they are a useful data point for alternate designs. I think the emphasis on access control (capability) performance and driver coverage are relevant for any production-grade microkernel.
I don't like the paging optimization described in section 4.5 [0]. It seems like a lot of added complexity for unequal gain.
In general, the authors make many good observations on the current designs of microkernels, particularly how the proliferation of small processes harms performance. Based on my reading of this paper and many others, I think there are some pragmatic considerations for building microkernel-based systems. The granularity of processes should be curtailed when performance is critical. Security is a spectrum, and such a system can still be more secure than the status quo. Limited kernels should be colocated next to processes again, not always across address spaces (since Meltdown), deferring to a cross-address space kernel on the harder-to-secure paths. If a process has a timer capability, and likely will for its remaining lifespan, an optimization could have a stub kernel accepting timer syscalls and forwarding the rest. Lastly, and this is a broader problem in most software, both code and state must be located in their proper places[1]. Use Parnas' criteria [2] for modular programming. If you believe in the power of the concept of microkernels, I have this to sell you; I believe it's even more basic and necessary. It's probably one of the most fundamental concepts we have on how to write good code.
[0] https://www.usenix.org/system/files/osdi24-chen-haibo.pdf [1] https://dl.acm.org/doi/10.1145/3064176.3064205 [2] https://wstomv.win.tue.nl/edu/2ip30/references/criteria_for_...
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