Hacker News Reader

Comment by jpm_sd | Hacker News Reader

This is a bunch of nonsense. Rust prefers static linking because it is predictable. These supposedly "huge" binaries are laughably small on a modern >1TB hard drive. If you're building a tiny embedded system, by all means optimize your builds system-wide, you have total control! But for a desktop, is this really a concern?

View on HN

If you add 9MB to each binary on the system by statically linking them, and your system runs 200 programs (including system services) on average, your system now uses about 2GB more memory (to be fair, probably not all the time but it does increase memory pressure needlessly). Shared libraries aren't just about storage space. They also provide page cache sharing (memory for a shared library is only mapped once and the mapping is shared by different programs).

A slight aside but they also provide the ability to apply security updates sanely to all programs using that library on the system (just update the library and restart the programs, as opposed to having to install a rebuilt version of every program that uses the library). Is this a game-changing feature? These days probably not, but it is (again) just needless waste.

And I say this as someone who is currently developing a shared library in Rust that will probably be included in a lot of distributions because I expect quite a fair amount of container runtimes will end up using it. (But I do also work for a Linux distribution.)

I used to think that way, but have come to the conclusion disk and memory issues should be handled by page / block level deduplication.

Security updates are a plus, but introducing bugs through a shared library is a minus.

I would prefer we focus on robust application sandboxing instead.

At the server datacenter level its pretty much how its handled anyway, you have isolated vm / containers sitting on deduped storage.

Sandboxing doesn't actually solve the biggest security problems, because most systems are there to run applications. That means that the interesting things on those systems are inside of some application's sandbox. It doesn't matter if I can't get root if I can get all the actually important assets on the system by cracking the application that actually processes those data.

... and in my experience, most application developers, and especially the developers who are the most truculently hostile to working with the system versions of libraries and the most likely to demand to bundle in their own copies for "stability" purposes, are really horrible about paying attention to security issues in their third-party dependencies.

When I'm being a user and a sysadmin rather than a developer or a packager, and I have the choice of trusting a developer versus trusting a packager, then, all else being equal, I will tend to trust the packager. Not that I trust either one that much.

But the linker doesn't try to keep code in a dedupe friendly format. I don't think this would help on a pile of Go/rust binaries.

Maybe there would be better sharing if I extracted the ELF sections first.

I just ran an experiment on the 20 largest items in my Mac's /usr/local/bin, many of which are Go binaries

    for file in `find /usr/local/bin -perm +u+x | xargs ls -SL | head -20`; do split -a4 -b4k $file `basename $file`; done
    ls | xargs md5 > md5.txt
    cut -d' ' -f4 md5.txt | sort | uniq -c | cut -c1-4 | sort | uniq -c

This gives: (number of 4kb blocks, frequency of sharing)

    128021    1
     12105    2
        13    3
         1    4
         1 1137

so about 10% of blocks are shared... once. And 1 blocks is shared 1137 (all zeroes).

To your second point, we still want fast security updates and more secure code even with sandboxing! EG, sandboxing would not help with heartbleed -- critical data leaked.

System wide shared libs is the opposite were we are trying to optimize space at the file level rather than block, and the linker instead optimizes for that along with all the other baggage of shared libs.

So if block level dedupe where the norm linkers would optimize for that instead. Coming from the .Net / Node world you don't statically link but you typically don't have shared libs, all the libs are in the same folder as the executable and dedupe works just fine there because you have just a bunch of duplicated files in different directories. Same with containers and Vm's all duplicating a bunch of the same system files. You get isolation and reuse because its done at a lower abstraction.

As far as security, again my point was a trade off, yes you could potentially get security updates faster along with breaking changes faster. If the sandbox apps had a good way to stay up to date, then they can update upstream after being integrated and tested with the app. If you have an app store of some sort it can watch for and notify to the authors of security issues in libs these use and prompt them to upgrade or be taken down.

I know the app store argument probably isn't popular around here but from my experience it is a far more secure solution especially for the non technical user. If something is really so widely used it should be a api provided by the OS, otherwise it should be bundled with the app individually and code sharing is done in source repos / build systems, at least thats my opinion after all these years.

> Same with containers and Vm's all duplicating a bunch of the same system files. You get isolation and reuse because its done at a lower abstraction.

Deduplication of containers is incredibly coarse-grained -- it's done a whole-layer basis which means that an update to any distribution package in a base image (resulting in a new layer hash when you rebuild on top of it) results in zero sharing between containers based on different versions of the base image. I am actually trying to rectify this problem with the whole OCIv2 effort -- but I wouldn't argue that today's containers make this problem non-existent. To be honest I hesitate to call the current model "deduplication" at all (yes, it might technically be deduplicated but it's not doing it to the degree you think it is).

And note that the page cache sharing you get from containers is also on the file level, so it's strictly no better than shared libraries (since the container filesystems contain shared libraries and that's what's being shared through the page cache).

You can't deduplicate if your 200 applications are using 20 minor versions times 50 mixes of compile flags. You're lucky if any two share the same output.

If your apps are using 20 different minor revisions and 50 different compile flags they prob can't share those libraries anyway? At least if some parts are the same they will dedupe at the block level even if files are different.

Indeed, you can't share in that case. The work of the distributor, as described in the article, is to make them share by unifying all those and requiring libraries to have stable ABI.

> memory issues should be handled by page / block level deduplication

I seem to recall ZFS deduplication needing tons of RAM. Wouldn't the memory deduplication you suggest similarly require even more memory?

Both Mac and Windows already do memory compression.

I don't know how ZFS works but the dedup I have seen runs in the background consuming minimal resources.

I would think if your mem-mapping a file that has been depdupped then its could just memap the already deduped block and cache in memory and not consume more memory if another file uses the same block and is memmapped but not sure if any OS does that.

> Security updates are a plus, but introducing bugs through a shared library is a minus.

The minus you mention is a consequence of "Move break fast things" webshit philosophy that's so pervasive these days.

Depending on undocumented behaviour and not properly documenting behaviour.

Edit: and forgot to mention ignorance towards security updates caused by modern PL package version locking etc..

It is a culture problem and technology can only do so much to fix that.

9MB is a lot. For scale: I have a rust application; assets (font + music), GUI via GPU, networking, unzipping, a bit of cryptography, it's all in there. 400 dependencies in total (yes, i don't like it).

By these metrics it's by far the largest rust application I've seen thus far. When fully optimized, it's 11MB in size.

I just used the metric from the article:

  > librsvg-2.so (version 2.40.21, C only) - 1408840 bytes
  > librsvg-2.so (version 2.49.3, Rust only) - 9899120 bytes

For your application, I imagine most of your application's code size is in your dependencies -- so if each crate was a separate shared library (for instance) then you'd end up reducing the amount of duplicated code if you had 50 applications that all needed to use RustCrypto.

Yes, it's a concern. Firstly, hard drive space isn't the only reason to make binaries small - you have RAM pressure, cache pressure, and bandwidth to save. Secondly and more importantly, waste adds up. If you replaced every binary on the system with a Rust equivalent - which, to listen to some advocates, is the eventual goal - you could end up with a base system that's many times larger.

In a larger sense, something that sets out to be a "systems programming language" needs to be exactly the sort of thing suitable for a tiny embedded system, even if it isn't running on one, because everything else builds on top of it. The attitude that "we have tons of power, why not waste it" just doesn't fly at the very lowest levels. You can write a desktop application in Python, and it's broadly fine - but try writing an OS kernel!

There are patches that let Rust run on ESP32 systems, so think it's entirely suitable for tiny embedded things. What makes it bloaty is the linked in standard library, but it's not an unsolvable crisis; you can dynlink against glibc, there is a crate for core rust IIRC. That'll get you reasonably sized rust applications.

And for writing kernels the same applies; without the stdlib, it gets a lot smaller very fast. I've done it, so I think I can count myself on having some experience there. The biggest part of my kernel is a 128KB scratch space variable it uses during boot as temporary memory until it has read the memory mappings from the firmware and bootstrapped memory management on a basic level. The remainder of the kernel (minus initramfs) is then about 1MB large, the largest part after the 128KB scratch space using about 96KB.

Regarding embedded, you generally only have one program. So dynamic linking buys you precisely nothing in that space.

Depends on if embedded refers to microcontrollers or just single board computers in various devices, but it wouldn't buy you much either way, yes.

>Firstly, hard drive space isn't the only reason to make binaries small - you have RAM pressure, cache pressure, and bandwidth to save.

FWIW, this is does not seem to be empirically true. The savings are possible in theory, but false in practice.

https://drewdevault.com/dynlib.html

The most used largest libraries, like libc and libpthread, would be dynamically linked by Rust anyways.

I seem to keep running out of space on my relatively small SSD where my OS is installed, so, yeah, it totally is a concern.

Buy a bigger ssd if you can, they're cheap. The last drive I bought was a 1TB Intel SSD for like $90.

But the pain point is on laptops like MacBooks which have comically small storage space for their price point. I think the base models have a measly 256GB SSD and charge crazy amounts for upgrades.

If applications were portable, then just put them on a different disk. This isn't rocket science, we've been doing it since the 80s.

Problem is that portable applications are an alien concept to Linux.

> Problem is that portable applications are an alien concept to Linux.

Static builds, AppImage, FlatPak, containers, etc would like to have a word with you.

Reply on news.ycombinator.com