John Baldwin wrote: > On Thursday 05 August 2004 01:04 am, Tim Robbins wrote: > >>Is there any particular reason why atomic_load_acq_*() and >>atomic_store_rel_*() are implemented with CMPXCHG and XCHG instead of >>MOV on i386/amd64 UP? > > > Actually, using mov instead of lock xchg for store_rel reduced performance in > some benchmarks Scott ran on an SMP machine, I'm guessing due to the higher > latency of locks becoming available to other CPUs. I'm still waiting for > benchmark results on UP to see if the change should be made under #ifndef SMP > or some such. > Your patch appears to slightly pessimize UP as well and SMP. ScottReceived on Fri Aug 06 2004 - 01:46:02 UTC
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