On Fri, Dec 1, 2023 at 6:42 AM Mathew Cherry G. <c...@bow.st> wrote: > > Hi, > > After some discussion with Jason, and re-reading the code and its > current state in code, I've come to the conclusion that it's in the > interest of brevity to remove everything in sys/kern/ and sys/uvm/ which > implement the "dynamic" part of uvm_hotplug(9). > > The top two reasons for this in my mind are: > > 1) There are no current users of the uvm_hotplug(9) KPI - balloon(9) > uses it, but the unplug is unstable (wasn't able to debug this) and > is thus disabled by default. > > 2) In order to do unplug without a balloon(9) like mechanism (eg: on > native), there's a lot more state management code needed within > uvm(9) - to make sure that RAM segments being unplugged have no > machine references (eg: pmap related, pointers from inactive page > tables, TLB pointers, etc. etc. ) > > This is a lot of per-architecture work, and there doesn't seem to be > much demand for this feature (at least I haven't seen any comment > related to this as a usecase). >
I agree with these points and if the "dynamic" part is not being used. I am assuming we are not completely removing the UVM_HOTPLUG option? > I believe that the project has had three useful purposes: > > 1) Demonstrated NetBSD code discipline - such a core part of the kernel > code was developed entirely in userspace prior to integration - and > due to the cross-compilable toolchain - it was done on Windows by > fox@! > > 2) The re-org forced better modularisation in the relevant > uvm/uvm_*.[hc] - ensuring even cleaner interfaces. > > 3) Demonstrated how TDD can reduce the pain of software dev. See: > > https://www.netbsd.org/gallery/presentations/santhosh/2017_AsiaBSDCon/ABC2017-P8B-uvm_hotplug-paper.pdf > > > If there's no specific objection to this I'll be working with Jason to > help make this is as painless as possible. > I am happy to offer any assistance needed to remove the related code if needed since I did work on the tests part of it. > > Many Thanks! > -- > MattC/(~cherry) Regards Santhosh
