manyworlds

4 ms·

1.
by manyworlds 7y ago
Ah okay, fine grained control of cache to minimize IO waiting is a good counterpoint. I actually have a lot of experience in this area, and I can say that effective readahead is a bit of a crapshoot. Only really works in trivial cases. Ulti
2.
by manyworlds 7y ago
Thanks for the examples but those all still seem like things vast majority of Linux users can do today, since vast majority of Linux users have root access. Both desktop and server. Mobile users like android don’t have root but I don’t see
3.
by manyworlds 7y ago
Sure but I don’t see any compelling use cases to motivate opening it up. Do you have an example of one? Even if the kernel opens it up without a compelling use case, it seems likely that distribution policy will keep it default locked to ro
4.
by manyworlds 7y ago
Hmm I don’t think this is the case, at least not when comparing fuse to in-kernel file systems. Having access to native VM structures only helps to the extent that you can avoid copies, yet in fuse, only one extra copy takes place. I think
5.
by manyworlds 7y ago
Unikernel or rump kernel would be better for that purpose
6.
by manyworlds 7y ago
Hmm I think bpf today is used in fully trusted environments. Kernel level verification is unnecessary except in untrusted containerized environments or when running untrusted applications, both use cases being relatively rare/specializ
7.
by manyworlds 7y ago
A BPF->kernel module compiler would ensure all necessary cleanup happens in __exit automatically
8.
by manyworlds 7y ago
Generally kernel code is also written to specific constraints. Out-of-tree drivers are usually bad at conforming and hypothetical out-of-tree webassembly drivers would be bad for similar reasons. Memory safety isn’t enough, using kernel int
9.
by manyworlds 7y ago
He’s not off the mark completely, you can maintain production safety by using a BPF->kernel module compiler. Unnecessary to have an entire JIT infrastructure in the kernel just to get the safety benefits of BPF.
10.
by manyworlds 7y ago
This is less about BPF vs native code, and more about the process model vs the event based model of application programming. Event based handling is inherently more efficient because it runs in the context of the caller, instead of requirin
11.
by manyworlds 7y ago
Doubtful. Webassembly is Turing complete, BPF isn’t. Running untrusted unbounded code in the kernel is not smart. BPF was invented with kernel constraints in mind, webassembly was invented with browser constraints in mind. Completely differ
12.
by manyworlds 7y ago
You can maintain production safety by using a BPF->kernel module compiler. This additionally removes the need to have the bpf compiler in the kernel, reducing both core size and vulnerability surface area. No reason BPF must imply JIT