Re: next meeting: Monday Jan 27th 10:00 - 12:00 CET

[Hannes Mehnert <hannes@xxxxxxxxxxx>]

Hey,

below are the notes from the meeting last week.

The next meeting is the upcoming Monday, January 27th 10:00 - 12:00 CET 
at https://meet.jit.si/MirageOS -- see our shared pad at 
https://pad.data.coop/To6IOSeNSOK9kFVlgo7XWw?both# for notes and agenda 
(add your talking points there) :)
Best,

Hannes

- Participants: Pierre, Hannes, Reynir, Sam, Pixie

### Performance: bytes vs. bigarray (cstruct)
- Pierre did some performance benchmarks. The results are confusing.
- VirtIO and spt are different: in virtio kvm/qemu does potential 
batching and queuing of packets; spt it is solo5 copying one-by-one
- reynir suggests to rewrite the C relay one-to-one in OCaml and take a 
look at the performance, figuring what the OCaml runtime costs are
- best performance is the Linux with a bridge between the two 
interfaces, that's our goal to compare numbers with -- it is as well a 
virtual machine with two interfaces doing the copying in kernel space -- 
MirageOS shouldn't be slower
- how/which profiling could we run there? statmemprof 
(https://github.com/robur-coop/memtrace-mirage -- only covers 
allocations, no computation (such as CRC)), landmarks 
(https://github.com/LexiFi/landmarks), SPT: we could also use `perf` 
utility from Linux
- it is still not very clear what is the bottleneck

### Building cross-compilers / OCaml 5 support
- Sam: they're merged in OCaml trunk
- Sam: backported to OCaml 5.3, plans to update ocaml-solo5 with 5.3 support
- Sam: some of the patches are only for ocaml-solo5
- Hannes: we can as well remove the 5.2.1 patches from ocaml-solo5 and 
move ahead for 5.3 -- if someone wants to usse 5.2.1 they can use the 
released ocaml-solo5 (1.0.0/1.0.1)
- Sam: the good news is that for OCaml 5.4 there will be really few 
patches needed
### maintenance-intent for MirageOS libraries
- unbounded growth of opam repository is unsustainable. Hannes started 
effort to prune uninstallable, broken and/or unmaintained packages. The 
`x-maintenance-intent` flag in opam files signals the intent to maintain 
packages: e.g. only the latest release etc.
- hannes main question here is whether there are any reservations of 
putting x-maintenance-intent: [ "(latest)" ] in the opam files for the 
MirageOS packages that we maintain (e.g. mirage, mirage-solo5, ...)
- pierre and reynir agree with putting the latest there (apart from 
ocaml-solo5)
- sometimes we have big breaking API changes where we likely want to 
keep the old and new versions (e.g. in ocaml-solo5 we have [ "(latest)" 
"0.8.(latest)" ]) - we can do that on a package-by-package basis when we 
do major breaking changes
### Defunctorise MirageOS
- hannes: don't want to pass "PCLOCK" "MCLOCK" "TIME" as functors
- hannes: the question is about naming, and about requiring the 
ptime/mtime libraries directly
- hannes: there's the opam package called mirage-clock (Mirage_clock), 
there we have a PCLOCK and a MCLOCK
- hannes: currently my suggestion is to name it Mirage_ptime and 
Mirage_mtime?
- hannes: and then the TIME interface should we rename it to 
Mirage_sleep? Mirage_sleep.sleep? Mirage_sleep.doit? Mirage_sleep.ns!
Currently:
```OCaml
(** Sleep operations. *)
module type S = sig
  val sleep_ns: int64 -> unit Lwt.t
  (** [sleep_ns n] Block the current thread for [n] nanoseconds, treating
      the [n] unsigned.  *)
end
```
### MirageOS and unikraft
- Pierre is curious what the state thereof is
- Sam: work is ongoing, some on private branches

### Meeting time is good?
- Sam mentions that the slot is good for him, but every time he is busy 
with some other thing
### Mollymawk
- robur got a grant for working on mollymawk from NLnet / EU tax payers
- we're excited to continue the work on it, and this will make (one path 
for) deployment of MirageOS unikernels easier


On 10/01/2025 16:02, Hannes Mehnert wrote:
> Hey,
>
> as a reminder on Monday morning we've our next meeting.
>
> On 07/01/2025 12:02, Hannes Mehnert wrote:
> > The next meeting is the upcoming Monday, January 13th 10:00 - 12:00 
> > CET at https://meet.jit.si/MirageOS -- see our shared pad at 
> > https://pad.data.coop/To6IOSeNSOK9kFVlgo7XWw?both# for notes and 
> > agenda (add your talking points there) :)
>
> Have a nice weekend,
>
> Hannes