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| -rw-r--r-- | lld/docs/NewLLD.rst | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/lld/docs/NewLLD.rst b/lld/docs/NewLLD.rst index 891160cded5..ff46af37435 100644 --- a/lld/docs/NewLLD.rst +++ b/lld/docs/NewLLD.rst @@ -128,6 +128,36 @@ between speed, simplicity and extensibility. However, in reality, we don't know any program that cannot link with our algorithm so far, so we are not too worried about the incompatibility. +Numbers You Want to Know +------------------------ + +To give you intuition about what kinds of data the linker is mainly working on, +this is the list of objects and their numbers LLD has to read and process +in order to link a very large executable +(Chrome with debug info which is roughly 2 GB in output size). + +- 13,000,000 relocations +- 6,300,000 symbols +- 1,800,000 sections +- 17,000 files + +LLD can produce the 2 GB executable in 15 seconds. + +These numbers vary depending on your program, but in general, +you have a lot of relocations and symbols for each file. +If your program is written in C++, symbol names are likely to be +pretty long because of name mangling. + +It is important to not waste time on relocations and symbols. + +In the above case, the total amount of symbol strings is 450 MB, +and inserting all of them to a hash table takes 1.5 seconds. +Therefore, if you causally add a hash table lookup for each symbol, +it would slow down the linker by 10%. So, don't do that. + +On the other hand, you don't have to pursue efficiency +when handling files. + Important Data Strcutures ------------------------- |
