Re: single-binary for execline programs?

From: alice <>
Date: Wed, 01 Feb 2023 07:22:14 +0100

On Wed Feb 1, 2023 at 6:58 AM CET, Dominique Martinet wrote:
> Laurent Bercot wrote on Wed, Feb 01, 2023 at 04:49:47AM +0000:
> > > It should be fairly easy to do something like coreutils'
> > > --enable-single-binary without much modification
> >
> > The subject has come up a few times recently,
> I believe I did my homework looking first -- are there other discussion
> channels than this list that one should be aware of?
> > so, at the risk of being
> > blunt, I will make it very clear and definitive, for future reference:
> >
> > No. It will not happen.
> Well, thanks for the clear answer, I'm glad I asked first!
> I'm a sore loser though, so I'll develop a bit more below. You've
> probably got better to do so feel free to just say you're not changing
> your mind or pointing me at the other discussions and I'll stop bugging
> you.
> > The fact that toolchains are becoming worse and worse is not imputable
> > to execline, or to the way I write or package software. It has always
> > been possible, and reasonable, to provide a lot of small binaries.
> > Building a binary is not inherently more complicated today than it was
> > 20 years ago. There is no fundamental reason why this should change; the
> > only reason why people are even thinking this is that there is an
> > implicit assumption that software always becomes better with time, and
> > using the latest versions is always a good idea. I am guilty of this
> > too.
> >
> > This assumption is true when it comes to bugs, but it becomes false if
> > the main functionality of a project is impacted.
> > If a newer version of binutils is unable to produce reasonably small
> > binaries, to the point that it incites software developers to change
> > their packaging to accommodate the tool, then it's not an improvement,
> > it's a recession. And the place to fix it is binutils.
> I definitely agree with this, I reported the problem in the bz I linked,
> and the reception has been rather good -- I trust we'll get back to
> smaller binaries in the next version or otherwise near future.
> > Multicall binaries have costs, mostly maintainability costs.
> > Switching from a multiple binaries model to a multicall binary model
> > because the tooling is making the multiple binaries model unusably
> > expensive is basically moving the burden from the tooling to the
> > maintainer. Here's a worse tool, do more effort to accommodate it!
> I guess it isn't completely free, but it certainly isn't heavy if the
> abstraction isn't done too badly.
> I'd go out a limb and say if you only support single-binary mode, some
> of the code could be simplified further by sharing some argument
> handling, but it's hard to do simpler than your exlsn_main wrapper so
> it'll likely be identical with individual programs not changing at all,
> with just an extra shim to wrap them all; it's not like busybox where
> individual binaries can be selected so a static wrapper would be dead
> simple.
> > Additionally to maintainability costs, multicall binaries also have a
> > small cost in CPU usage (binary starting time) and RAM usage (larger
> > mappings, fewer memory optimizations) compared to multiple binaries.
> > These costs are paid not by the maintainer, but by the users.
> Hmm, I'd need to do some measurements, but my impression would be that
> since the overall size is smaller it should pay off for any pipeline
> calling more than a handful of binaries, as you'll benefit from running
> the same binary multiple times rather than having to look through
> multiple binaries (even without optimizing the execs out).
> Memory in particular ought to be shared for r-x pages, or there's some
> problem with the system. I'm not sure if it'll lazily load only the
> pages it requires for execution or if some readahead will read it all
> (it probably should), but once it's read it shouldn't take space
> multiple times, so multiple binaries is likely to take more space when
> you include vfs cache as soon as you call a few in a row; memory usage
> should be mostly identical to disk usage in practice.
> Anyway, I'll concede that in doubt, let's call it a space vs. speed
> tradeoff where I'm favoring space.
> > Well, no. If having a bunch of execline binaries becomes more expensive
> > in disk space because of an "upgrade" in binutils, that is a binutils
> > problem, and the place to fix it is binutils.
> I shouldn't have brought up the binutils bug.
> Even almost 1MB (the x86_64 version that doesn't have the problem,
> package currently 852KB installed size + filesystem overhead..) is
> still something I consider big for the systems I'm building, even
> without the binutils issue it's getting harder to fit in a complete
> rootfs in 100MB.
> Just looking at the s6 suite (s6, s6-rc, execline, skalibs,
> s6-linux-init) I'm looking at a 3MB increase (because I won't be able to
> get rid of openrc for compatibility with user scripts it'll have to live
> in compat hooks...) ; being able to shave ~700KB of that would be
> very interesting for me (number from linking all .c together with a
> dummy main wrapper, down 148KB)
> (s6-* dozen of binaries being another similar target and would shave a
> bit more as well, build systems being similar I was hoping it could go
> next if this had been well received)

out of (somewhat off-topic) curiosity, what is the layout here?
the general answer to such a case generally is:
"sure, it's 3MB. but it's a well-implemented well-oiled well-used 3MB, and the
'business software' is hundreds of times that", but maybe this is something

given the (below) talk of inexperienced users, it makes me wonder if everything
is in this 100mb, or if it's only a reserved rootfs for you while the rest if

> > > In the long run this could also provide a workaround for conflicting
> > > names, cf. old 2016 thread[4], if we'd prefer either running the
> > > appropriate main directly or re-exec'ing into the current binary after
> > > setting argv[0] appropriately for "builtins".
> >
> > There have been no conflicts since "import". I do not expect more name
> > conflicts in the future, and in any case, that is not an issue that
> > multicall binaries can solve any better than multiple binaries. These
> > are completely orthogonal things.
> It's a step further, but I don't think it's orthogonal.
> If all the code is in a single binary you could have internal priorities
> to builtins easily as there would be no need to mess with PATH or a
> separate install prefix.
> > > (I assume you wouldn't like the idea of not installing the individual
> > > commands, but that'd become a possibility as well. I'm personally a bit
> > > uncomfortable having something in $PATH for 'if' and other commands that
> > > have historically been shell builtins, but have a different usage for
> > > execline...)
> >
> > You're not the only one who is uncomfortable with it, but it's really a
> > perception thing. There has never been a problem caused by it. Shells
> > don't get confused. External tools don't get confused. On this aspect,
> > Unix is a lot more correct and resilient than you give it credit for. :)
> Shells and external tools would definitely be fine, they're not looking
> there in the first place.
> I think you're underestimating what users who haven't used a unix before
> can do though; I can already picture some rummaging in /bin and
> wondering why posix-cd "doesn't work" or something... We get impressive
> questions sometimes.

i definitely feel for you there (in regards to inexperienced user questions),
but i'd say that generally very low level (relatively) systems integration
software is not the place where "inexperienced user support" is in-scope. the
easiest answer is that if somebody runs into such a scenario, they'll just have
to learn the answer to the question, not have an "answer" pre-implemented for
them via a workaround (such as this one) that removes it.

that is to say, resolving this (question-)case specifically would not be a
benefit for execline itself.

> --
> Dominique
Received on Wed Feb 01 2023 - 07:22:14 CET

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