[Lldb-commits] [PATCH] D103504: Improve performance when parsing symbol tables in mach-o files.

[Greg Clayton via Phabricator via lldb-commits]

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Some larger projects were loading quite slowly with the current LLDB on macOS and macOS simulator builds. I did some instrument traces and found 3 main culprits:

- a LLDB timer that was put into a function that was called too often
- a std::set that was keeping track of the address of symbols that were already added
- a unnamed function generator in ObjectFile that was going slow due to allocations

In order to see this in action I ran the latest LLDB on a large application with many frameworks using the following method:

(lldb) script import time; start_time = time.perf_counter()
(lldb) file Large.app
(lldb) script print(time.perf_counter() - start_time)

I first range "sudo purge" to clear the system file caches to simulate a cold startup of the debugger, followed by two iterations with warm file caches.

Prior to this fix I was seeing the following timings:

17.68 (cold)
14.56 (warm 1)
14.52 (warm 2)

After this fix I was seeing:

11.32 (cold)
8.43 (warm 1)
8.49 (warm 2)


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D103504

Files:
  lldb/source/Core/Module.cpp
  lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp
  lldb/source/Symbol/ObjectFile.cpp

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