CCLS doesn't scale well to much higher thread counts

MaskRay / ccls

C/C++/ObjC language server supporting cross references, hierarchies, completion and semantic highlighting

Apache License 2.0

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CCLS doesn't scale well to much higher thread counts #957

Open lanza opened 6 months ago

lanza commented 6 months ago

My work machine is an AMD Epyc 9634 with 166 threads. While indexing an LLVM build with clang and mlir enabled and ~10k items to be indexed, ccls often hovers between 1300% and 4000% CPU usage with index.threads set to either 0 or 166.

Any idea what the bottleneck in CCLS is?