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jmmv | 2 months ago
The answer to an ever-increasing size of binaries was always "let's make the infrastructure scale up!" instead of "let's... not do this crazy thing maybe?". By the time I left, there were some new initiatives towards the latter and the feeling that "maybe we should have put limits much earlier" but retrofitting limits into the existing bloat was going to be exceedingly difficult.
joatmon-snoo|2 months ago
- google-wide profiling: the core C++ team can collect data on how much of fleet CPU % is spent in absl::flat_hash_map re-bucketing (you can find papers on this publicly)
- crashdump telemetry
- dapper stack trace -> codesearch
Borg literally had to pin the bash version because letting the bash version float caused bugs. I can't imagine how much harder debugging L7 proxy issues would be if I had to follow a .so rabbit hole.
I can believe shrinking binary size would solve a lot of problems, and I can imagine ways to solve the .so versioning problem, but for every problem you mention I can name multiple other probable causes (eg was startup time really execvp time, or was it networked deps like FFs).
MaskRay|2 months ago
As my https://maskray.me/blog/2023-05-14-relocation-overflow-and-c... (linked by author, thanks! But I maintain lld/ELF instead of "wrote" it - it's engineer work of many folks)
Quoting the relevant paragraphs below:
## Static linking
In this section, we will deviate slightly from the main topic to discuss static linking. By including all dependencies within the executable itself, it can run without relying on external shared objects. This eliminates the potential risks associated with updating dependencies separately.
Certain users prefer static linking or mostly static linking for the sake of deployment convenience and performance aspects:
* Link-time optimization is more effective when all dependencies are known. Providing shared object information during executable optimization is possible, but it may not be a worthwhile engineering effort.
* Profiling techniques are more efficient dealing with one single executable.
* The traditional ELF dynamic linking approach incurs overhead to support [symbol interposition](https://maskray.me/blog/2021-05-16-elf-interposition-and-bsy...).
* Dynamic linking involves PLT and GOT, which can introduce additional overhead. Static linking eliminates the overhead.
* Loading libraries in the dynamic loader has a time complexity `O(|libs|^2*|libname|)`. The existing implementations are designed to handle tens of shared objects, rather than a thousand or more.
Furthermore, the current lack of techniques to partition an executable into a few larger shared objects, as opposed to numerous smaller shared objects, exacerbates the overhead issue.
In scenarios where the distributed program contains a significant amount of code (related: software bloat), employing full or mostly static linking can result in very large executable files. Consequently, certain relocations may be close to the distance limit, and even a minor disruption (e.g. add a function or introduce a dependency) can trigger relocation overflow linker errors.
unknown|2 months ago
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Filligree|2 months ago
lenkite|2 months ago
btilly|2 months ago
Early on Google used dynamic libraries. But weird things happen at Google scale. For example Google has a dataset known, for fairly obvious reasons, as "the web". Basically any interesting computation with it takes years. Enough to be a multiple of the expected lifespan of a random computer. Therefore during that computation, you have to expect every random thing that tends to go wrong, to go wrong. Up to and including machines dying.
One of the weird things that becomes common at Google scale, are cosmic bit flips. With static binaries, you can figure out that something went wrong, kill the instance, launch a new one, and you're fine. That machine will later launch something else and also be fine.
But what happens if there was a cosmic bit flip in a dynamic library? Everything launched on that machine will be wrong. This has to get detected, then the processes killed and relaunched. Since this keeps happening, that machine is always there lightly loaded, ready for new stuff to launch. New stuff that...wind up broken for the same reason! Often the killed process will relaunch on the bad machine, failing again! This will continue until someone reboots the machine.
Static binaries are wasteful. But they aren't as problematic for the infrastructure as detecting and fixing this particular condition. And, according to SRE lore circa 2010, this was the actual reason for the switch to static binaries. And then they realized all sorts of other benefits. Like having a good upgrade path for what would normally be shared libraries.
tmoertel|2 months ago
See for more: https://google.github.io/building-secure-and-reliable-system...
bfrog|2 months ago
darubedarob|2 months ago
loeg|2 months ago