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6915da34a60f23c69221399ae5a72159f1374b9a- Date:
- Message:
- The traditional LL/SC atomics perform poorly on modern arm64 systems with many CPU cores. With the recent conversion of the sched lock to a mutex some systems appear to hang if the sched lock is contended. ARMv8.1 introduced an LSE feature that provides atomic instructions such as CAS that perform much better. Unfortunately these can't be used on older ARMv8.0 systems. Use -moutline-atomics to make the compiler generate function calls for atomic operations and provide an implementation for the functions we use in the kernel that use LSE when available and fall back on LL/SC. Fixes regressions seen on Ampere Altra and Apple M2 Pro/Max/Ultra since the conversion of the sched lock to a mutex. tested by claudio@, phessler@, mpi@ ok patrick@
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