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2713083386
This patches libsigsegv to not check the stack vma on Linux, since that involves reading procfs, and we make very heavy use of sigsegv. This eliminates most of urbit's performance discrepancy between Linux and MacOS. These are the benchmarks used; note this is a local MBP vs a cloud Linux server, and the MBP is almost certainly faster hardware. We take two benchmarks, one of which decrements 10 million times and the other simply allocates 125MB of memory. These are the results: cpu-heavy == =/ n 10.000.000 |-(?~(n n $(n (dec n)))) mem-heavy == =a (bex 1.000.000.008) macos, cpu-heavy: 6 seconds macos, mem-heavy: 1 second linux-before, cpu-heavy: 30 seconds linux-before, mem-heavy: 160 seconds linux-after, cpu-heavy 9 seconds linux-after, mem-heavy 1.3 seconds This represents a 3x speedup for the cpu-heavy operation and a 120x speedup for the memory-heavy operation. This check was used to try to distinguish stack overflow from other forms of segmentation fault. In the comments in src/handler-unix.c, it describes three heuristics it uses, depending on what's available from the OS. In the linux-i386 case, all three are availble, so we simply disable the slow one. This correctly recognizes stack overflow if you simply alloca(10000000000). |
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