[lld] [lld][MachO]Multi-threaded i/o. Twice as fast linking a large project. (PR #147134)

[John Holdsworth via llvm-commits]

johnno1962 wrote:

Sorry, I edited the message so you wouldn't have been bugged about it. I'm tracking these reports and updating my newer follow up PR https://github.com/llvm/llvm-project/pull/157917 to do the following:

1) All new code compiled in #if LLVM_ENABLE_THREADS is set so it can be seen where the changes were from this PR.
2) The new PR moves to use madvise() instead of the ad-hoc page referencing code I wrote which should avoid SIGSEGVs if the buffer is deallocated.
3) A new property SerialBackgroundQueue().stopAllWork to be used to stop background workers when there is no further call for them. Usually the background "page-in" threads have completed first but it seems with this troublesome test this is not always the case and buffers stored in the static input file cache are being deallocated while being referenced.


https://github.com/llvm/llvm-project/pull/147134