Robert Haas <[email protected]> writes:
> [ lots of interesting stuff about WAL optimization snipped ]
> ... Second, they aren't really using locks, unless you count
> bus locks - they appear to have implemented most or all of it via
> CAS-based lock-free algorithms, which is probably well-justified
> optimization effort.
FWIW, I'm pretty suspicious of claims that lock-free data structures
will be some kind of magic bullet. As far as I can tell, a very large
part of our contention problems on many-core machines stem from the CPUs
fighting over cache line ownership. Avoiding an explicit lock in favor
of hardware primitive test-and-modify instructions isn't going to do a
darn thing to improve that. And contorting the algorithms until they
fit into what's portably available in that line could easily be a net
loss.
regards, tom lane
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