Re: The Case for Rust (in the base system)

From: Tomoaki AOKI <junchoon_at_dec.sakura.ne.jp>
Date: Sun, 21 Jan 2024 05:10:24 UTC
On Sat, 20 Jan 2024 21:14:59 -0700
Alan Somers <asomers@freebsd.org> wrote:

> On Sat, Jan 20, 2024, 8:44 PM Warner Losh <imp@bsdimp.com> wrote:
> 
> >
> >
> > On Sat, Jan 20, 2024, 7:20 PM Alan Somers <asomers@freebsd.org> wrote:
> >
> >> On Sat, Jan 20, 2024 at 7:06 PM Tomoaki AOKI <junchoon@dec.sakura.ne.jp>
> >> wrote:
> >> >
> >> > On Sat, 20 Jan 2024 15:31:23 -0700
> >> > Warner Losh <imp@bsdimp.com> wrote:
> >> >
> >> > > On Sat, Jan 20, 2024 at 11:45 AM Aleksandr Fedorov <
> >> wigneddoom@yandex.ru>
> >> > > wrote:
> >> > >
> >> > > > What about external dependencies?
> >> > > >
> >> > > >
> >> https://github.com/Axcient/freebsd-nfs-exporter/blob/master/Cargo.toml#L19
> >> > > >
> >> https://github.com/asomers/gstat-rs/blob/master/gstat/src/main.rs#L20
> >> > > >
> >> > > > Is there any plan for which crates we should take into the base
> >> system?
> >> > > >
> >> > > > We have had C++ in base for many years, but I don’t see any good
> >> libraries
> >> > > > for CLI, logging, JSON, etc.
> >> > > >
> >> > > >
> >> > > >
> >> https://doc.rust-lang.org/rustc/platform-support.html#tier-1-with-host-tools
> >> > > >
> >> > > > Where is the support for Freebsd as a primary platform? ARM, RISC-V,
> >> > > > Power? Should we rewrite devd?
> >> > > >
> >> > > > I think we need to start by providing official repositories (e.g
> >> > > > git.FreeBSD.org/rust.git or git.FreeBSD.org/go.git)
> >> > > > for different languages that include stable bindings to the system
> >> API:
> >> > > > - sysctl
> >> > > > - libgeom
> >> > > > - libifconfig
> >> > > > - netgraph
> >> > > > - jail
> >> > > > - etc.
> >> > > >
> >> > > > So that it’s not just some anonymous on crates.io that represents
> >> these
> >> > > > bindings, but our community.
> >> > > > Officially, with support for a stable ABI for releases, security
> >> patches,
> >> > > > etc.
> >> > > >
> >> > > > After this, it will be possible to think about which components to
> >> include
> >> > > > in the base system.
> >> > > >
> >> > > > I would be glad to see a more modern language than C in the
> >> database, but
> >> > > > I’m afraid that it will be like with C++,
> >> > > > that we will get a couple of daemons and utilities and that’s all.
> >> > > >
> >> > >
> >> > > These are all good questions that need good answers, though
> >> necessarily to
> >> > > get started.
> >> > >
> >> > > But the other question that occured to me after my last posting was
> >> "What
> >> > > about build integration?"
> >> > > How much of the rust automation do we take in vs how much do we drive
> >> from
> >> > > a future bsd.rust.mk.
> >> > > I can sketch out bsd.rust.mk (to pick an arbitrary name, we'd likely
> >> need
> >> > > one for what we traditionally
> >> > > think of as libraries (which may or may not map 1:1 onto crates: we
> >> could
> >> > > have c callable libraries
> >> > > written in rust in the future, for example) and one for binaries.
> >> > > Initially, though, if we go with the
> >> > > 'make rust tests possible' then we'd likely need the appropriate
> >> packages
> >> > > installed for whatever
> >> > > dependencies we'd have in the tests. This would give us a taste for
> >> what
> >> > > we'd need to do for
> >> > > base, I'd think. Once we had that notion, I can easily see there
> >> needing to
> >> > > be some sort of
> >> > > rust bindings for ATF/kyua as one of the first libraries / crates that
> >> > > would test that aspect of
> >> > > the build system. That all would be up to the people writing the
> >> tests in
> >> > > rust, I'd imagine.
> >> > >
> >> > > While I could jot out the basics of this integration (so one could
> >> just add
> >> > > the rust
> >> > > tools to a subdir or subdirs, include the bsd.rust.mk or whatever
> >> and then
> >> > > it would build
> >> > > if rust is enabled, and would emit a warning it was skipped because
> >> rust
> >> > > was disabled).
> >> > > We'd find out if this is workable or not and iterate from there. But
> >> that
> >> > > would also require
> >> > > active participation from the rust advocates to make it a reality: I
> >> can
> >> > > put together the
> >> > > build infrastructure for the disabled case, but likely can't on my
> >> own do
> >> > > the rust enabled
> >> > > case. I'd be happy to work with someone to do that, but I'm not going
> >> to be
> >> > > able to do
> >> > > that myself: my need for rust is slight, my knowledge of rust is
> >> weak, etc.
> >> > > Working with
> >> > > someone (or ideally several someones), though it could become
> >> reality. So
> >> > > please contact
> >> > > me if you'd like to work on this.
> >> > >
> >> > > Warner
> >> >
> >> > One way to go could be moving programs rewritten with rust to ports.
> >> > There are some programs (not in rust, though) moved to ports, like rcs.
> >>
> >> I've already done this with a few, though I didn't delete the C
> >> versions from base.
> >> usr.bin/gstat => sysutils/gstat-rs
> >> tools/regression/fsx => devel/fsx
> >>
> >
> > So
> > % size `which gstat-rs` `which gstat`
> >      text     data   bss       dec        hex   filename
> >   2094442   176472   568   2271482   0x22a8fa   /usr/local/sbin/gstat-rs
> >     19350     1180    41     20571     0x505b   /usr/sbin/gstat
> > % file `which gstat-rs` `which gstat`
> > /usr/local/sbin/gstat-rs: ELF 64-bit LSB pie executable, ARM aarch64,
> > version 1 (FreeBSD), dynamically linked, interpreter /libexec/ld-elf.so.1,
> > FreeBSD-style, stripped
> > /usr/sbin/gstat:          ELF 64-bit LSB pie executable, ARM aarch64,
> > version 1 (FreeBSD), dynamically linked, interpreter /libexec/ld-elf.so.1,
> > for FreeBSD 15.0 (1500008), FreeBSD-style, stripped
> > 8:36pm brazos:[3826]> ldd `which gstat-rs` `which gstat`
> > /usr/local/sbin/gstat-rs:
> > libgeom.so.5 => /lib/libgeom.so.5 (0x60fd38647000)
> > libthr.so.3 => /lib/libthr.so.3 (0x60fd38b57000)
> > libgcc_s.so.1 => /lib/libgcc_s.so.1 (0x60fd39af1000)
> > libc.so.7 => /lib/libc.so.7 (0x60fd3be6f000)
> > libbsdxml.so.4 => /lib/libbsdxml.so.4 (0x60fd3a009000)
> > libsbuf.so.6 => /lib/libsbuf.so.6 (0x60fd3a55e000)
> > /usr/sbin/gstat:
> > libdevstat.so.7 => /lib/libdevstat.so.7 (0x448867cd000)
> > libgeom.so.5 => /lib/libgeom.so.5 (0x4488710b000)
> > libedit.so.8 => /lib/libedit.so.8 (0x44887f8d000)
> > libtinfow.so.9 => /lib/libtinfow.so.9 (0x44888aab000)
> > libncursesw.so.9 => /lib/libncursesw.so.9 (0x44889c60000)
> > libc.so.7 => /lib/libc.so.7 (0x4488aaf4000)
> > libkvm.so.7 => /lib/libkvm.so.7 (0x44888f77000)
> > libbsdxml.so.4 => /lib/libbsdxml.so.4 (0x4488ba02000)
> > libsbuf.so.6 => /lib/libsbuf.so.6 (0x4488c68d000)
> > libelf.so.2 => /lib/libelf.so.2 (0x4488ca45000)
> >
> > So that looks scary, like rust is 100x larger binaries...  But at runtime
> > it's about the same:
> > USER    PID   %CPU %MEM   VSZ   RSS TT  STAT STARTED         TIME COMMAND
> > imp   14735    0.0  0.0 14140  4828  0  S+   20:38        0:00.04 gstat
> > imp   14766    1.3  0.0 15772  6256  0  S+   20:39        0:00.02 gstat-rs
> >
> > So the runtime size is at least in the same ballpark (still larger, but
> > not crazy larger). More CPU too,
> > but that's just a polling artifact I think (other times gstat had some,
> > and gstat-rs didn't).
> >
> > Why is the rust binary so much larger? Are the rust runtime and
> > dependencies statically linked?
> >
> 
> Yes, that's a large part of it. Rust libraries are usually statically
> linked (though they don't have to be). For example, in the output above,
> notice that gstat-rs does not link to ncurses. That's because the
> equivalent library is statically linked in instead. Also, rust programs by
> default include goodies like stack unwinding on panic, which takes extra
> code too. But that can be turned off if you really want to save space.
> -Alan

Because of these, I feel rust fits best for commercial DOS apps, not
Unix-based OS'es. In DOS era, AFAIK, most programs installed required
libraries at the same directory which its executable is installed,
regarless exactly same libraries are installed in other directory by
other softwares. This looks very similar as current rust default,
except that libraries are statically linked in rust.

But rust seems to have (non-default) option to create shared libraries
by --crate-type=dylib and --crate-type=cdylib options [1].

Charlie Li pointed me this page before [2].

Without this kind of options, linking rust codes with C/C++ codes would
be nonsense. (Whichever should have this kind of options, but rust ABI
seems to be too unstalbe [changing rapidly] to implement it in C/C++
side.)

I'd not yet dug in deep enough to conclude or write rust code myself,
so just a thought for now, but I currently think we would better wait
for rust ABI to be stabilized. Until then, rust codes in ports may
increase and maintainers good at rust would increase, too.
It would greatly help to investigate how to introduce rust codes in
base.

[1] https://doc.rust-lang.org/reference/linkage.html

[2]
https://lists.freebsd.org/archives/freebsd-ports/2023-September/004546.html

-- 
Tomoaki AOKI    <junchoon@dec.sakura.ne.jp>