4 ms·

I work on C++ code at a large tech company. My workflow is such that I compile and run tests often after I made incremental changes. I feel like I often wait fo

I work on C++ code at a large tech company. My workflow is such that I compile and run tests often after I made incremental changes. I feel like I often wait for the linker for ages. I am wondering if linking could be sped up. I feel like a lot of the steps mentioned here could be cached for instance.

int0x80 8y ago
If it does LTO it gets worse. Maybe you can disable it for dev, if its enabled?
mehrdadn 8y ago
Can/do you have incremental linking enabled?
pjmlp 8y ago
Depends what you use as C++ compiler. Visual C++ supports incremental compilation and linking. https://blogs.msdn.microsoft.com/vcblog/2018/03/14/build-time-improvement-recommendation-turn-off-map-use-pdbs/ https://blogs.msdn.microsoft.com/vcblog/2018/03/14/build-tim... https://blogs.msdn.microsoft.com/vcblog/2014/11/12/speeding-up-the-incremental-developer-build-scenario/ https://blogs.msdn.microsoft.com/vcblog/2014/11/12/speeding-... https://blogs.msdn.microsoft.com/vcblog/2018/01/04/visual-studio-2017-throughput-improvements-and-advice/ https://blogs.msdn.microsoft.com/vcblog/2018/01/04/visual-st... https://blogs.msdn.microsoft.com/vcblog/2016/10/05/faster-c-build-cycle-in-vs-15-with-debugfastlink/ https://blogs.msdn.microsoft.com/vcblog/2016/10/05/faster-c-...
johncolanduoni 8y ago
I've seen (sometimes drastic) performance improvements when switching to LLVM's new linker lld[1]. It works quite well on both Linux and Windows in my experience. [1]: https://lld.llvm.org/ https://lld.llvm.org/
jstimpfle 8y ago
I, too, have been wondering that. On a high level, a linker does these things: - Read in objects file and parse linking information (needed symbols etc) - Do some in-memory calculations - resolving symbols and some other stuff. Simple graph theory. Is there any need for more than O(n log n) runtime?. - Write out object files I don't think anything should take so long. No caching needed. I read the series on linkers by gold's author, where significant speedups were claimed. And also, that object-oriented C++ was the right approach to software architecture. I strongly disagree with that second point and didn't understand too much from the article series to be honest. So I am not surprised at all that there are today even much faster linkers.

int0x80 8y ago

If it does LTO it gets worse. Maybe you can disable it for dev, if its enabled?

mehrdadn 8y ago

Can/do you have incremental linking enabled?

pjmlp 8y ago

Depends what you use as C++ compiler. Visual C++ supports incremental compilation and linking. https://blogs.msdn.microsoft.com/vcblog/2018/03/14/build-time-improvement-recommendation-turn-off-map-use-pdbs/ https://blogs.msdn.microsoft.com/vcblog/2018/03/14/build-tim... https://blogs.msdn.microsoft.com/vcblog/2014/11/12/speeding-up-the-incremental-developer-build-scenario/ https://blogs.msdn.microsoft.com/vcblog/2014/11/12/speeding-... https://blogs.msdn.microsoft.com/vcblog/2018/01/04/visual-studio-2017-throughput-improvements-and-advice/ https://blogs.msdn.microsoft.com/vcblog/2018/01/04/visual-st... https://blogs.msdn.microsoft.com/vcblog/2016/10/05/faster-c-build-cycle-in-vs-15-with-debugfastlink/ https://blogs.msdn.microsoft.com/vcblog/2016/10/05/faster-c-...

johncolanduoni 8y ago

I've seen (sometimes drastic) performance improvements when switching to LLVM's new linker lld[1]. It works quite well on both Linux and Windows in my experience. [1]: https://lld.llvm.org/ https://lld.llvm.org/

jstimpfle 8y ago

I, too, have been wondering that. On a high level, a linker does these things: - Read in objects file and parse linking information (needed symbols etc) - Do some in-memory calculations - resolving symbols and some other stuff. Simple graph theory. Is there any need for more than O(n log n) runtime?. - Write out object files I don't think anything should take so long. No caching needed. I read the series on linkers by gold's author, where significant speedups were claimed. And also, that object-oriented C++ was the right approach to software architecture. I strongly disagree with that second point and didn't understand too much from the article series to be honest. So I am not surprised at all that there are today even much faster linkers.