[wahern]

So as the designer you're telling me that your lock-free (excluding the locking necessary for updating the page tables) and possibly wait-free algorithm (unsure on the last part), simply can't be modeled as a transactional memory algorithm? If you're willing to claim that, I'll acquiesce. Because excluding the low-level details and the context of what's happening, the barrier algorithms look exactly like what you'd get trying to implement, e.g., the N-word transactional memory copying algorithms from 30+ years ago--in particular what Hoare laid out in the paper proving the universality of the LL/SC primitive--in a way that works on x86 for the JVM.

Regarding performance: number of allocations is not the same as transactional throughput. If you can also claim that the object system and VM subsystem of your JVM has no overhead over a traditional lock-based system (which doesn't use extensive mapping tricks, nor needs as many atomic operations), _or_ if you can show me TPC benchmarks where C4 is faster than the other existing locking collectors, I'll acquiesce.

Otherwise, I'm quite comfortable sticking to my guns.

I think what you've written is exceptional in numerous regards. And I don't mean to diminish the work in the slightest, but to only counter the hype--namely, that the algorithm uses techniques unknowable to others, or (as sometimes discussed elsewhere) that it's solved the problem of implementing a generic transactional memory model using regular x86 primitives.

[giltene]

Let's see:

1. We never claimed the algorithm uses "techniques unknowable by others" (um, we published the algorithm, so it's obviously knowable by others)

2. We never claimed to have implemented generic transactional memory using regular x86 primitives.

So you can consider this made up hype countered.