From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jonathan Corbet Date: Wed, 15 Jun 2022 11:25:12 -0600 Subject: [Ksummit-discuss] [MAINTAINERS SUMMIT] How far to go with eBPF In-Reply-To: <20220615170407.ycbkgw5rofidkh7x@quack3.lan> References: <20220615170407.ycbkgw5rofidkh7x@quack3.lan> Message-ID: <87h74lvnyf.fsf@meer.lwn.net> Jan Kara writes: > Yeah. Related to this is the fact that this way eBPF hooks become de-facto > API of the kernel with all the implications for required stability. It is > one thing to use eBPF for kernel introspection / monitoring (there > occasional breakage is kind of expected by userspace) and another to enable > hardware with it where people just expect things to work... Relevant to this whole thing, I think, is the multigenerational LRU discussion at LSFMM: https://lwn.net/Articles/894859/ One aspect that was only dropped in as a response to a question is that the plan is to add a BPF hook to manage the movement of pages between LRU generations; this will be done because nobody really knows how to come up with an optimal solution to that problem for the general case. That's about as core as it gets and, if users are tweaking memory management with BPF, that will surely achieve ABI status in short order. Beyond that, though, is the temptation to say "we don't have to figure out this hard problem, we'll just add a BPF hook and let the users find a solution for themselves". The line between providing a useful means for expert users to optimize their systems and skipping out on our own duty to optimize things is not always clear, at least to me. jon