My Go executable files are still getting larger

https://www.cockroachlabs.com/blog/go-file-size-update/

by alexbilbie • 5 years ago

264 169 5 years ago

brainzap• 5 years ago

Is there a bug report for this?

ainar-g• 5 years ago

Probably falls under the umbrella issue filed by Rob Pike… back in 2013[1]. But that's the umbrella issue, and it's probably better for the Cockroach people to file a new one mentioning their findings, but don't quote me on that.

[1] https://github.com/golang/go/issues/6853

jordanlewis• 5 years ago

Rob Pike filed this issue for it after the first incarnation of the article was released: https://github.com/golang/go/issues/36313

marcus_holmes4• 5 years ago

I always wonder if this is the flip side of the fast compilation?

It would be nice to be able to decide on those trade-offs ourselves. I mostly write web servers in Go, which (as the article says) are executed rarely, so init time really doesn't matter to me. But I've been looking at writing some desktop apps in Go, and then init time will matter.

throwaway8943452• 5 years ago

I mostly write web servers in Go, which (as the article says) are executed rarely, so init time really doesn't matter to me.

Presumably a few mb of disk usage also doesn't matter then? I also write web services, but I do care about the init time precisely because I want to be deployments to take as little time as possible so that we can deploy (and rollback) many times per day with relatively simple automation. That said, the bottleneck to fast deployments isn't the binary starting up, but the machine pulling the executable artifact, so the binary sizes do matter to me. That said, very often these executable artifacts are a Docker image, which tend to come with a lot more bloat than one will find in a Go binary, so step 1 is getting your Go binary on a scratch image.

cpuguy83• 5 years ago

Unless you are running these in containers, then that time adds up (assuming you are using go-based container runtime implementations, as most people are).

marcus_holmes4• 5 years ago

Yeah, it's a trade-off. At the moment the longest part of my deploy is copying the new executable to the server. I'd trade a couple of seconds of init time for a smaller executable because that would result in a faster deploy.

I don't use Docker to deploy, because it's just a single executable file (and a bunch of templates, though I'm looking at embedding those). One of the reasons I'm reluctant to go down the Docker road is because it's going to add more time to my deployment.

remus• 5 years ago

I always wonder if this is the flip side of the fast compilation?

I don't think there's an easy either-or answer to questions like this, but broadly language design seems to be about finding a sweet spot while balancing lots of trade offs, so to get fast compiles you're going to make trade-offs in other areas of the language and implementation. I imagine if the compilation time budget was higher there'd be some more space for binary pruning passes.

rplnt• 5 years ago

Fast compilation is great for development and testing. Both local and in CI.

marcus_holmes4• 5 years ago

totally agree. Being able to hit the "run this test" and not having to wait for it to compile is awesome :)

But if there some flags to tell the compiler to compile slowly and produce a smaller executable, that would be awesome for final builds that need to be shipped across the internet.

kortex• 5 years ago

At least for CLI-tool-sorta-programs, I find Rust and Go emit vaguely similar sized binaries, a few Mb is typical. The biggest cause is of course static linking.

However, once you exceed the 10-20Mb regime, I seem to find more 20-200Mb Go bins in the wild. This can be misleading, since the Go world is a fan of packing assets into binaries, eg for web GUIs.

What dings Go bins on init time is the Go runtime. Still, it's rarely noticeable unless you are firing thousands of times a second.

jerf3• 5 years ago

More likely the flip side of statically compiling every library in. Even if the Go compiler did the equivalent of -Os you'd still be getting binaries that people were complaining about.

I know for a good long time Go wasn't even stripping out unused functions, e.g., if you used any of the "strings" standard module you got the whole thing compiled in. I don't know if that's still the case, but it would be another source of size problems.

I'm also not sure why you're talking about init time; binary size doesn't necessarily factor in to that very much. The things that make the Go binaries large also tend to lean in favor of faster initialization anyhow. A lot of these binaries won't even necessarily be read in to memory, or have to stay there in the event of swap pressure, since they're already disk-backed memory pages that can be never loaded in the first place, or cheaply evicted by the virtual memory system if space is needed.

gray_-_wolf3• 5 years ago

I always wonder if this is the flip side of the fast compilation?

Go is cheating a bit on this one by heavily caching everything. Building in fresh container is quite slow (ok, maybe not c++ slow but still much slower then C).

Always having to build anything due to static linking does not help either.

whateveracct2• 5 years ago

It's the flip side to never exposing configuration flags and instead always making a Worse is Better decision for everyone.

It mirrors their GC philosophy.

nappy-doo4• 5 years ago

No. The two are mostly orthogonal. Sure, you can take a longer time to compile small binaries, but that's not what Go does. OP is talking about internal data structures Go uses for introspection and GC. The amount of time time spent compiling would have a marginal effect on the size of those structures.

londons_explore2• 5 years ago

It's time for debug info like this to be sent to "onlinesymbolserver.com", encrypted with a hash of the binary.

Then, whenever a debugger connects to a binary, it can simply download the symbols as required.

And for the 99.9% who don't need debug info, it isn't needlessly shipped.

Microsoft invented this in the 90's...

pjmlp2• 5 years ago

Around 1992 Borland C++ would use macro based code generation for generic code in BIDS 1.0, sounds familiar?

I guess it is just a tradition with Go, rediscovering history.

agumonkey• 5 years ago

On the memory capacity of social structures.pdf

the_mitsuhiko3• 5 years ago

Sadly go doesn’t care about DWARF which would allow them to reuse already existing infrastructure.

icholy2• 5 years ago

Go uses DWARF.

jeffbee5• 5 years ago

I don't think this information in Go is used for debugging alone. It's also used by mallocgc and other parts of the runtime. This is why you will see "gentraceback" in the profiles of busy Go servers. It's not because your program is printing a lot of stack traces, it's because stack walking is a core part of the GC, and because some logic in the runtime refers to the names of functions to branch around special cases.

londons_explore2• 5 years ago

I assume those bits of runtime could be modified to have other special markers on the functions they need to special case...

haberman2• 5 years ago

The sum of the sizes reported by go tool nm does not add up to the final size of the Go executable.
At this time, I do not have a satisfying explanation for this “dark” file usage.

The author's journey of starting with "nm --size", discovering "dark" bytes, and wanting to attribute them properly, is exactly what led me to create and invest so much effort into Bloaty McBloatface: https://github.com/google/bloaty

Bloaty's core principle is that every byte of the file should be attributed to something, so that the sum of the parts always adds up to the total file size. If we can't get detailed symbol, etc. information for a given region of the file, we can at least fall back to describing what section the bytes were in.

Attributing all of the bytes requires parsing much more than just the symbol table. Bloaty parses many different sections of the binary, including unwind information, relocation information, debug info, and the data section itself in an attempt to attribute every part of the binary to the function/data that emitted it. It will even disassemble the binary looking for references to anonymous data (some data won't make it into the symbol table, especially things like string literals).

I wrote up some details of how Bloaty works here: https://github.com/google/bloaty/blob/master/doc/how-bloaty-.... The section on the "Symbols" data source is particularly relevant here:

I excerpted two symbols from the report. Between these two symbols, Bloaty has found seven distinct kinds of data that contributed to these two symbols. If you wrote a tool that naively just parsed the symbol table, you would only find the first of these seven:"

The author's contention that these "dark" bytes are "non-useful" is not quite fair. There are plenty of things a binary contains that are useful even though they are not literally executable code. For example, making a binary position-independent (which is good for security) requires emitting relocations into the binary so that globals with pointer values can be relocated at program load time, once the base address of the binary is chosen. I don't know if Go does this or not, but it's just one example.

On the other hand, I do agree that the ability to produce slim binaries is an important and often undervalued property of modern compiler toolchains. All else being equal, I much prefer a toolchain that can make the smallest binaries.

Bloaty should work reasonably well for Go binaries, though I have gotten some bug reports about things Bloaty is not yet handling properly for Go: https://github.com/google/bloaty/issues/204 Bloaty is just a side thing for me, so I often don't get as much time as I'd like to fix bugs like this.

parhamn4• 5 years ago

In other words, the Go team decided to make executable files larger to save up on initialization time.

I mean... Im genuinely curious if this is a "we have extra engineering resources and can explore/complain about this" or "we have a client who is running cockroachdb and can't handle a 172mb binary install for a database server".

Is there really someone out there who installs Cockroach (a global distributed auto-sharded database) and thinks twice about 172mb of disk space?

Sure, it'd be nice to have smaller binaries but outside of some embedded applications Go's binaries sizes are well within the nothing-burger range for most compute systems.

gtirloni• 5 years ago

It affects the download and instantiation time for containers.

henvic• 5 years ago

One word: trade-offs.

mikepurvis• 5 years ago

I worry about that for 10gb omnibus containers, not so much for <500mb.

parhamn4• 5 years ago

The article says they don't really care about initialization time though, which is right.

Remember: cockroachdb is always synchronizing data across the cluster, that 175mb of ingress to start up a DB node, probably pales in comparison to data synchronization/relocations that happen on a cluster. Which is why worrying about ingress/egress costs over binary size is nonsense here too.

The bandwidth you need to run a distributed database cluster could download 172mb binary in milliseconds. If your node initiation time for DB failovers needs anything faster, you're doing something wrong.

There are stakeholders to this problem, Cockroach probably isn't one.

Thaxll• 5 years ago

172MB for a Docker image that contains a DB is pretty small, Go Docker image are among the smallest because Go binary can run with minimal deps.

sagichmal2• 5 years ago

This isn't an interesting or convincing argument because it revolves around a non-satisfiable metric. No matter the size of an artifact, this line of reasoning can always be used to claim it's too big and needs to be smaller.

Touche2• 5 years ago

Go binary size makes it not an option for wasm.

gen2203• 5 years ago

There are go variants for this. See tinygo [1], which targeted embedded originally (iirc) but now also targets wasm.

So you’re definitely correct that core Go is not an option, but options exist within the “greater metropolitan area” that’s built up around downtown.

These are among the benefits of having a relatively simple language and a 1.0 compatibility commitment, I think.

[1] https://tinygo.org/ their FAQ is quite good.

patrickaljord• 5 years ago

Why not? If you use wasm for a small library need in your web app, then sure, go doesn't make sense. But if your whole app is coded in wasm like a game, then it's probably ok I guess as the app will be heavy to load regardless.

blinkingled2• 5 years ago

So tomorrow if the Go team doubled your binary size by adding "darkest bytes" area with garbage in it your response would be to question the users's inability to be ok with it and not the Go team's choice and reasoning?

whateveracct2• 5 years ago

Feels like the Go team could just...expose a flag?

Which they are loathe to do

parhamn4• 5 years ago

If you think those are the alternatives, I don't think the rest of this discussion will go well.

dvfjsdhgfv3• 5 years ago

Is there really someone out there who installs Cockroach (a global distributed auto-sharded database) and thinks twice about 172mb of disk space?

I think it is exactly this mindset that caused the current situation (that the 2/3 of the compiled binaries are useless to the users).

dbt002• 5 years ago

(that the 2/3 of the compiled binaries are useless to the users).

That the bytes are not visible in the symbol table is inarguable, that they are useless is a highly contentious statement and very probably wrong.

parhamn4• 5 years ago

The alternative isn't avoiding fixing it. The alternative is a boring bug report on github with actual stakeholders discussing the best strategies and trade offs.

This is only on HN's homepage because of the langauge flame wars. It's a garbage post.

kreetx• 5 years ago

Couldn't the dark bytes just be shipped as a separate file - for those who need it?

skywhopper3• 5 years ago

Is it clear that the “dark bytes” are “useless” debug information? It sounds like it’s just stuff not in the symbol table.

tyingq• 5 years ago

I did keep waiting for some point in the blog post where they would null out the "dark bytes" and see if/how the binary runs.

stabbles• 5 years ago

Every time, 70% of a couple hundred megabytes are copied around for no good reason and someone needs to pay ingress/egress networking costs for these file copies. That is quite some money being burned for no good reason!

Meanwhile half of the world is pushing images by nvidia, intel and amd around for their machine learning software:

Intel OneAPI runtime libraries: 4.74GB (or 18.4GB for compilers) CUDA runtime libraries: 1.92GB (or 4.2GB for compilers)

These go binaries are still relatively small

bbatha• 5 years ago

Most of the time, especially with the docker hub rate limiting changes people are or should be using their cloud provider's mirror or running their own mirror. Actually ingressing the docker image into your network should happen once in most production setups.

boredpandas777• 5 years ago

Maybe Go optimizing for serverless with reduced init time?

blinkingled2• 5 years ago

We can call this the “dark file usage” of Go binaries, and it occupies between 15% and 33% of the total file size inside CockroachDB.
Sadly, the removal of pclntab in Go 1.16 actually transferred the payload to the “dark” bytes.

I surely would have expect better from programming language designers/developers than this. Sounds like they just moved the problem from one place to another.

rob74• 5 years ago

I'll hold my judgement until someone manages to actually find out what this "dark" space is (quote from the article: "At this time, I do not have a satisfying explanation for this “dark” file usage").

tedunangst• 5 years ago

Every time, 70% of a couple hundred megabytes are copied around for no good reason and someone needs to pay ingress/egress networking costs for these file copies.

Just zero them out and they'll compress to nothing. Even better, with a sparse file aware tool like tar, they won't even use disk space.

njuw• 5 years ago

starting in Go 1.16, the pclntab is not present any more, and instead is re-computed from other data in the executable file.

Does anyone have a source for this? As it still appears to be there

- Go 1.15 https://i.imgur.com/3YlZGOk.png

- Go 1.16 https://i.imgur.com/gGYsj32.png

nappy-doo4• 5 years ago

No source needed -- you're right. The author's looking in the symbol table, and in 1.16 the Go linker set the size of runtime.pclntab to 0. If the OP used nm to look at their binary, they'd have seen that pclntab is still there. They author has apparently revised their article to address some of this (yet still draw some incorrect conclusions).

(This is derived from Russ' discussion above.)

daitangio• 5 years ago

Go static linking is a great happy idea for a Java guy trapped in the Classpath Dependency Hell (or C# / DLL Hell).

It is a very annoying thing for a C++ programmer, which can dynamically link operating system libraries at will.

skrebbel• 5 years ago

You mean a C++ programmer who does not care whether their program works on anybody else's computer?

synergy20• 5 years ago

in that case you can happily static-link c++ programs, which probably will be smaller than go binary.

kstenerud• 5 years ago

"DLL Hell" was coined in the early days of Windows (before C#), and originally referred to C and C++ dynamic library problems.

anthk3• 5 years ago

Go's static linking idea comes from plan9 C compilers, a few years before Java. We owe a lot from plan9:

- Go's design, based on both C compilers and Inferno's limbo

- /proc

- utf-8

- 9p

eklitzke• 5 years ago

/proc does not come from plan9: http://dtrace.org/blogs/eschrock/2004/06/25/a-brief-history-...

kissgyorgy• 5 years ago

Python is still more wildly used / popular language, but I never seen a Python container for a real project which was less than 1GB.

rataata_jr• 5 years ago

I've seen ones in MBs with alpine

simtel20• 5 years ago

Have you tried basing one on distroless? That has turned out pretty small python containers for me.

dbt002• 5 years ago

I'm guessing you're doing ML here? Because the core python runtime is far smaller than that.

kornholi• 5 years ago

Yeah, ML libraries are a huge offender. The Torch 1.8.1 manylinux wheel is 1.6G unpacked, with 1.1G going to CUDA support.

masklinn• 5 years ago

Alpine containers for P3 go down to about 60MB for the baseline. Everything else is what you added in.

CPython doesn't generate anything, and the binary installers (including docs and all) are about 30MB. Hell, the 64b embeddable package for windows (https://docs.python.org/3/using/windows.html#the-embeddable-...) is 16MB uncompressed.

rsc10• 5 years ago

This article is full of misinformation. Just a few representative things:

- The expansion of pclntab in Go 1.2 dramatically improved startup time and reduced memory footprint, by letting the OS demand-page this critical table that is used any time a stack must be walked (in particular, during garbage collection). See https://golang.org/s/go12symtab for details.

- We (the Go team) did not “recompress” pclntab in Go 1.15. We did not remove pclntab in Go 1.16. Nor do we have plans to do either. Consequently, we never claimed “pclntab has been reduced to zero”, which is presented in the article as if a direct quote.

- If the 73% of the binary diagnosed as “not useful” were really not useful, a reasonable demonstration would be to delete it from the binary and see the binary still run. It clearly would not.

- The big table seems to claim that a 40 MB Go 1.8 binary has grown to a 289 MB Go 1.16 binary. That’s certainly not the case. More is changing from line to line in that table than the Go version.

Overall, the claim of “dark bytes” or “non-useful bytes” strikes me as similar to the claims of “junk DNA”. They’re not dark or non-useful. It turns out that having the necessary metadata for garbage collection and reflection in a statically-compiled language takes up a significant amount of space, which we’ve worked over time at reducing. But the dynamic possibilities in reflection and interface assertions mean that fewer bytes can be dropped than you’d hope. We track binary size work in https://golang.org/issue/6853.

An unfortunate article.

rsc10• 5 years ago

An easily obtained apples-to-apples¹ table:

    $ for i in $(seq 3 16); do
        curl -sLo go1.$i.tgz https://golang.org/dl/go1.$i.linux-amd64.tar.gz
        tar xzf go1.$i.tgz go/bin/gofmt
        size=$(ls -l go/bin/gofmt | awk '{print $5}')
        strip go/bin/gofmt
        size2=$(ls -l go/bin/gofmt | awk '{print $5}')
        echo go1.$i $size $size2
    done
    
    go1.3  3496520 2528664
    go1.4² 14398336 13139184
    go1.5  3937888 2765696
    go1.6  3894568 2725376
    go1.7  3036195 1913704
    go1.8  3481554 2326760
    go1.9  3257829 2190792
    go1.10 3477807 2166536
    go1.11 3369391 2441288
    go1.12 3513529 2506632
    go1.13 3543823 2552632
    go1.14 3587746 2561208
    go1.15 3501176 2432248
    go1.16 3448663 2443736
    $

Size fluctuates from release to release, but the overall trendline is flat: Go 1.16 binaries are roughly where Go 1.3 binaries were.

At the moment, it looks like Go 1.17 binaries will get a bit smaller thanks to the new register ABI making executable code smaller (and faster).

¹ Well, not completely. The gofmt code itself was changing from release to release, but not much. Most of the binary is the libraries and runtime, though, so it's still accurate for trends.

² Turns out we shipped the go 1.4 gofmt binary built with the race detector enabled! Oops.

knz4219• 5 years ago

Strip removes the symbol tables and DWARF information.

But still, the sum of all the bytes advertised in symbol tables for the non-DWARF data does not sum up to the stripped size. What's the remainder about?

I am reminded of how early versions of MSWord were embedding pages of heap space in save files that were not relevant to the document being saved, just because it made the saving algorithm simpler. For all we know, the go linker could be embedding random data.

gampolt• 5 years ago

https://lobste.rs/s/gvtstv/my_go_executable_files_are_still_... here is apple to apple compare for compile cockroachDB 1.0 across go 1.8 to 1.16, it's 20% smaller not bigger go 1.8 = 58,099,688 go 1.16 = 47,317,624

knz4219• 5 years ago

As explained in another comment below, it's a good thing when all the byte usage is represented in the ELF section headers or the symbol tables.

The DWARF data is currently so represented, and so was pclntab prior to 1.16.

Today, the DWARF data is still present; the symbol for pclntab has an advertized size of zero, and the amount of data not represented in the symbol table and ELF section headers has grown.

If the 73% of the binary diagnosed as “not useful” were really not useful, a reasonable demonstration would be to delete it from the binary and see the binary still run. It clearly would not.

Probably not if all of it was removed at once.

It could be that just 5% of it is useful and removing all of it would produce a non-working binary. What does the experiment prove exactly?

Look you can claim that "having the necessary metadata for garbage collection and reflection in a statically-compiled language takes up a significant amount of space" but without clear evidence of how much space that is, with proper accounting of byte usage, this claim is non-falsifiable and thus of doubtful value.

rsc10• 5 years ago

Look you can claim that "having the necessary metadata for garbage collection and reflection in a statically-compiled language takes up a significant amount of space" but without clear evidence of how much space that is, with proper accounting of byte usage, this claim is non-falsifiable and thus of doubtful value.

I respectfully disagree. I believe there is value in pointing out the false claims in a long blog post even when there isn't time to write a full-length rebuttal.

erincandescent• 5 years ago

As explained in another comment below, it's a good thing when all the byte usage is represented in the ELF section headers or the symbol tables.

It's an ELF binary; all that's relevant are the program/segment headers and dynamic table. The section headers and non-dynamic symbol table are just there for orthogonality and to make the debugger's life a little easier (and the debugger would much prefer DWARF data and doesn't care about the section headers, tbh)

arp2427• 5 years ago

Look you can claim that "having the necessary metadata for garbage collection and reflection in a statically-compiled language takes up a significant amount of space" but without clear evidence of how much space that is, with proper accounting of byte usage, this claim is non-falsifiable and thus of doubtful value.

The article made the claim that 70% of space is wasted "dark bytes". The article should prove the claim, which it did not. It's an extraordinary claim that really requires more evidence than just an off-hand napkin calculation and talk about mysterious "dark bytes".

It takes very little time to write up something that's wrong.

It takes much more time to write a detailed rebuttal.

What you're doing here is pretty much the same trick quacks, young-earth creationists, and purveyors of all sorts of pseudo-scientific claims pull whenever they're challenged. Any fool can claim the earth is 6,000 years old. Proving that it's actually several billions years old requires deep insight in multiple branches of science. People stopped doing this after a while as it's so much effort and pointless as they're not listening anyway, so now they pull the "aha, you didn't falsify my claim about this or that bullshit I pulled out of my ass therefore I am right" zinger and think they look Very Smart And Scientific™.

But that's not how it works.

Also just outright disbelieving people like this is rather rude. You're coming off really badly here and your comment has the strong implication that Russ is outright lying. Yikes!

jerf3• 5 years ago

Go has a complete accounting of what all the bytes are. You can read them for yourself in the compiler, as it is open source, and trace through where every byte comes from, if you like. It isn't exactly in a broken down table precisely to the specs of what knz42 wants, but the info is all there. There's nothing hidden here.

Oh, you don't want to do that? That's not a surprise. Neither do I. Definitely not on my agenda today.

But I'm not making wild accusations. If you're going to, you probably shouldn't be surprised when we're not exactly impressed.

The compiler is all open, and as such things go, fairly easy to read. "As such things go" is definitely doing some heavy lifting there, but, still, for a compiler of a major language, it's a relatively easy read.

The vague intimation that there's something hidden and sneaky going on is hard to give much credence to.

skywhopper3• 5 years ago

You are getting ridiculous at this point. Probably some things could be done to improve the binary size, but the maintainers of Go don’t have unlimited time. Russ showed that Go is not growing binary sizes. Your article is misleading and at best poorly worded. When you add more code your binaries get bigger. Is that a surprise to you? If Go binary size is a critical concern for you, you could be helping solve the problem, but you are just complaining.

knz4219• 5 years ago

The expansion of pclntab in Go 1.2 dramatically improved startup time and reduced memory footprint [...]

yes this is acknowledged in the OP

We (the Go team) did not “recompress” pclntab in Go 1.15.

There's now less redundancy in the funcdata, so in my book less redundancy = more compression.

We did not remove pclntab in Go 1.16.

Correct; it is not "removed"; instead the advertised size of the symbol has been reduced to zero. Maybe the data is still there, but it's not accounted any more.

Changed in the text. (The correction is already present in the original version of the analysis, and the cockroach labs copy should be updated soon)

we never claimed “pclntab has been reduced to zero”, which is presented in the article as if a direct quote.

Correct, there was indeed no such claim. Removed the quotes and rephrased that paragraph.

If the 73% of the binary diagnosed as “not useful” were really not useful, a reasonable demonstration would be to delete it from the binary and see the binary still run. It clearly would not.

1) the phrase "non-useful" was a mistake. There is no definite proof it is non-useful, as you pointed out. Corrected in the text.

2) see discussion below - the demonstration is more complicated than that, as removing 100 bytes where just 1 byte is necessary will break the executable in the same way as removing 100 necessary bytes.

I think the proper next step here is to acknowledge that the problem is not "usefulness" but rather accountability.

The big table seems to claim that a 40 MB Go 1.8 binary has grown to a 289 MB Go 1.16 binary. That’s certainly not the case. More is changing from line to line in that table than the Go version.

Correct. Added a note to emphasize this fact.

Overall, the claim of “dark bytes” or “non-useful bytes” strikes me as similar to the claims of “junk DNA”. They’re not dark or non-useful.

Let's forget about "non-useful", this was a mistake and will be corrected. The word 'dark' is still relevant however. The adequate comparison is not "junk DNA", but instead "dark silicon":

https://ieeexplore.ieee.org/abstract/document/6307773

We're talking about a general % of executable size that's necessary for a smaller % of use cases in program function.

I'm all for trade-offs, but IMHO they should be transparent.

returningfory22• 5 years ago

In this case, what is the point the blog post is trying to make?

The title of the post is "Go Executable Files Are Still Getting Larger". Upon further reading and conversation here it seems this is possibly not true, nor what the post is about. If we believe Russ's comments, Go executable sizes haven't increased much in general. Perhaps the reason you're seeing increases in Cockroach DB is because you keep writing more code for Cockroach DB?

Now the point has shifted to this notion of "dark bytes". So the article is about ... how the way you previously diagnosed the contents of binaries doesn't work anymore? That's fine and legitimate, but it seems like the point is over-extrapolated to become a criticism of the Go team.

mort963• 5 years ago

The term "dark silicon" refers to silicon that's not (currently) in use, such as when you have a workload which only exercises one arithmetic unit of one core even if you have 8 cores with 4 arithmetic units each (only one arithmetic unit is "lit up", 63 are "dark"). There's no reason to believe that what you're calling "dark bytes" isn't actively used while executing the program.

rsc10• 5 years ago

Another thing I noticed in the revised blog post on a second skim, regarding this claim:

Every time, 70% of a couple hundred megabytes are copied around for no good reason and someone needs to pay ingress/egress networking costs for these file copies.

That 70% includes the ELF/DWARF metadata that is easily removed from the binary using strip. It's true that the DWARF info in particular has gotten larger in recent releases, because we've included more information to make debuggers work better. I don't think it has grown quite as rapidly as the table indicates - I think some of the rows already have some of the debug metadata removed in "Raw size".

Regardless, I would hope that anyone sensitive to networking costs at this level would be shipping around stripped binaries, so the growth in accurate DWARF info should not be relevant to this post at all.

That is, the right comparison is to the "Stripped" column in the big table. If you subtract out the strippable overheads and you take the "Dark + pclntab" as an accurate representation of Go-specific overhead (debatable but not today), then the situation has actually improved markedly since Go 1.12, which would have been current in April 2019 when the first post was written.

Whereas in Go 1.12 the measured "actual program" was only about 40% of the stripped binary, in Go 1.16 that fraction has risen to closer to 55%.

This is a marked-up copy of the table from the dr-knz.net revised post that at time of writing has not yet made it to cockroachlabs.com: https://swtch.com/tmp/cockroach-blog.png

I think the numbers in the table may be suspect in other ways, so I am NOT claiming that from Go 1.12 to Go 1.16 there has actually been a 15% reduction in "Go metadata overhead". I honestly don't know one way or the other without spending a lot more time looking into this.

But supposing we accept for sake of argument that the byte counts in the table are valid, they do not support the text or the title of the post. In fact, they tell the opposite story: the stripped CockroachDB binary in question has gotten smaller since April 2019, and less of the binary is occupied by what the post calls "non-useful" or "Go-internal" bytes.

knz4219• 5 years ago

Thanks Russ for that additional insight.

I would hope that anyone sensitive to networking costs at this level would be shipping around stripped binaries, so the growth in accurate DWARF info should not be relevant to this post at all.

Good point. I removed that part from the conclusion.

If you subtract out the strippable overheads and you take the "Dark + pclntab" as an accurate representation of Go-specific overhead [...] then the situation has actually improved markedly since Go 1.12 [...] Whereas in Go 1.12 the measured "actual program" was only about 40% of the stripped binary, in Go 1.16 that fraction has risen to closer to 55%.

Ok, that is fair. I will attempt to produce a new version of these tables with this clarification.

the stripped CockroachDB binary in question has gotten smaller since April 2019, and less of the binary is occupied by what the post calls "non-useful" or "Go-internal" bytes.

There's an explanation for that, which is that the crdb code was also reduced in that time frame.

hatuio3• 5 years ago

In env without swap, the binary size should/might block relative amount of ram.

Might it be possible to stream binaries or to detect junks which could be unloaded like an json parser which is only needed when reading json

remram3• 5 years ago

Without swap, you mean without virtual memory or without a swap partition/file?

Because even without a swap partition/file, the whole executable will not block physical memory, but will page in/out as needed. And whole sections of it will never be loaded at all.

johnisgood• 5 years ago

Yeah, I do not understand those numbers. I just compiled one of my Go projects with version 1.13.8 and version 1.16.3. The size was 8.3 MB (6.5 MB after stripping), and 8.0 MB (5.8 MB after stripping) respectively.

rsc10• 5 years ago

The article has been updated to avoid calling the bytes "not useful" and to address the narrow, specific points I raised, but it is still generally suspect.

Over on Lobsters, zeebo took the time (thanks!) to build the same version of CockroachDB with various historical Go toolchains, varying only the toolchain, and found that if anything the Go executables are getting smaller over time, in some cases significantly so.

            v1.0          v20.2.0
    1.8     58,099,688    n/a
    1.9     57,897,616    314,191,032
    1.10    57,722,520    313,669,616
    1.11    48,961,712    233,170,304
    1.12    52,440,168    236,192,600
    1.13    50,844,048    214,373,144
    1.14    50,527,320    212,699,656
    1.15    47,910,360    201,391,416

https://lobste.rs/s/gvtstv/my_go_executable_files_are_still_...

The title of the article ("My Go executable files are still getting larger") appears to be literally untrue, at least read as a critique of Go itself. If they are getting larger, it's because new code is being added, not because the Go runtime or compiler is degrading in some way over time.

knz4219• 5 years ago

The title of the article ("My Go executable files are still getting larger") appears to be literally untrue, at least read as a critique of Go itself. If they are getting larger, it's because new code is being added, not because the Go runtime or compiler is degrading in some way over time.

Yes this is a fair assessment, although I find it surprising (and enlightening) that you refer to “a critique of Go”. At no moment was the intent to critique Go specifically; the entire analysis is made of observation of the results of combining Go with specific (and varying) amounts of source code.

In any case, based on this discussion I have decided to amend the title and emphasize in the conclusion that the absolute size of the code+data for a fixed amount of source code has decreased between go 1.15 and 1.16.

edit: This is relevant to this discussion: https://sneak.berlin/20191201/american-communication/

josvazg-yc• 5 years ago

Indeed.

You do NOT write an article talking about "dark bytes" and a 70% "not useful" piece of binary for an Open Source project.

Specially one such as Golang where you can easily reach out to the creators at https://groups.google.com/g/golang-dev to ask for help understanding what your experiment tools can't explain...

Eg. """ Hey guys I am doing some digging with "such and such" tools and found that 70% of my binary size has no explanation. BTW this binary is Cockroach DB, an well known program in the Go ecosystem. How can I find out what are those bytes for? Is there any documentation about it, other than the source code itself? Or maybe some tooling that explains it? Or some other set of tools I should be using instead or on top of my current setup? """

I mean... there is no defense possible after writing such an article IMHO. Why didn't you ask first?

Having said that, when you deviate from the ubiquitous C standards for calling conventions and binary format layout, that comes with a price. I totally get that Go had to take such path, because Go binaries embed a non trivial runtime dealing, at the very least, with goroutines & GC support. But the price is there nonetheless: As you are not using a standard, you cannot rely on pre-existing tooling or documentation. You have to write your own.

It is understandable that writing such binary dissection documentation or tooling (or both) might not be a top priority compared to other more pressing matters for the Go Language. But this kind of thing becomes technical debt and as such, the longer you take to pay it, the more expensive it becomes. For instance: - This happened, and might have damaged the Go Language reputation, at least temporarily for some people. - I am surprised how could the Go team (or community) achieve improvements at all in the binary size work without tools to properly dissect binaries or detailed documentation. I am guessing it relied on the original programmers of those bits to have a very clear idea of the binary layout uploaded in their brains, so they did not need to re-grok all the sources again... with time that becomes more and more difficult, people forget stuff, move to other projects, etc.

I think it would be wise to prioritize this somehow. If the Go team cannot take it for now, maybe they can promote it as a good Go community project to be done ASAP, and promise to help the takers with all info and reviews needed.

Or maybe the article writers should take up the challenge, to fully redeem themselves ;-p

u678u• 5 years ago

We need more initContainers where the big shared system libraries are in a separate container that is cached locally. I feel like history is repeating.

EdiX• 5 years ago

From the same data scientist that concluded non-linear growth from two single data points...

jeffbee5• 5 years ago

This article should be renamed “what is Chesterton‘s fence?” And the author should have realized their mistake right after typing “at this time I don’t know what it is used for”.

bradfitz2• 5 years ago

To promote my own tool, https://github.com/bradfitz/shotizam lets you drill down into why Go binaries are large without having to make up terms like "dark bytes".

knz4219• 5 years ago

This code, if I'm reading it right, uses the symbol table and ELF section headers.

As explained in OP, the sum of sizes advertised in the symtable and ELF section headers does not add up to the final binary size. The shotizam tool is thus blind to that difference.

nappy-doo4• 5 years ago

This sounds like a bug to me, not nefarious intent.

arp2427• 5 years ago

If physicists can have dark matter and dark energy, then why can't we have dark bytes? Why should we let the physicists have all the dark fun?

saati• 5 years ago

Because it's genuinely unknown what those are, figuring out what these bytes are is just a deep dive into the opensource go compiler at worst or just asking around on some go channels for much less effort.

cristaloleg2• 5 years ago

Sadly it doesn't work with Go 1.16 :(( https://github.com/bradfitz/shotizam/issues/10

bradfitz2• 5 years ago

Oh right :)

tediousdemise• 5 years ago

It seems to be a challenge to add zero-overhead features to programming languages.

Poor design decisions result in a language that gets extremely bloated over time, forcing you to use features that you don’t want to.

The better approach is to make these features optional, such as through a standard library.

arp2427• 5 years ago

Moreover, consider that these executable files fly around as container images, and/or are copied between VMs in the cloud, thousands of times per day! Every time, 70% of a couple hundred megabytes are copied around for no good reason and someone needs to pay ingress/egress networking costs for these file copies. That is quite some money being burned for no good reason!

Does the author think the Go authors are stupid blubbering idiots who someone missed this huge elephant-sized low-hanging fruit? Binary sizes have been a point of attention for years, and somehow missing 70% wasted space would be staggeringly incompetent.

Reminds me of the time in high school when one of the my classmates ended up with a 17A doorbell in some calculations. I think he used the wrong formula or swapped some numbers. The teacher, quite rightfully, berated him for not actually looking at the result of his calculation and judging if it's roughly in the right ballpark, as 17A is a ludicrous amount of power for a doorbell. Anyone can see that's just widely wrong.

If this story had ended up with 0.7%, sure, I can believe that. 7%? Unlikely and I'd be skeptical, but still possible I suppose. *70%* Yeah nah, that's just as silly as a 17A doorbell.

This huge 70% number should have been a clue to the author themselves too that they've missed something.

superdisk• 5 years ago

In a world where electron reigns supreme, 70% waste isn't unthinkable

jeffbee5• 5 years ago

After looking into the size of the CockroachDB binary, the magnitude of the plank in the author's eye becomes clear. This iceberg is ridiculously bloated. Much of the space is coming from the static data of geographic projections that, I assume, basically nobody needs. This includes a single init function that is 1.4MB of machine code from 6MB of auto-generated source code. Then there's the entire AWS SDK, with a static definition of every service AWS offers, by name, and in what regions, by name. Nevermind the Azure SDK. There are three implementations of protocol buffers in here: gogo in Go and Google's in both Go and C++. There are at least four SQL parsers in here, including vitess's and another one for crdb in Go.

Last but by no means least there are in total 13MB of autogenerated functions of the colexec package, each of which is over 100KB long, which are autogenerated and share virtually all of their code. These are an obscene waste of code space and undoubtedly de-deuplicating this code would not just reduce code size but also speed up the program, due to icache trashing.

orangechairs• 5 years ago

Hey all -- Cockroach Labs blog editor here. Based in part on the feedback we received from this community, we have retracted the post. The blog post link above will take you the retraction, where we share what we've learned from this experience.

My Go executable files are still getting larger

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