New rwlock committed -- enabling elision for it needs better default tuning first

[Torvald Riegel]

On Tue, 2017-01-10 at 12:33 +0100, Torvald Riegel wrote:
> When testing on x86_64 TSX, my first guess for a workload that may test
> the quality of the adaption code and the default tuning parameters
> turned out to be a case where elision failed and produces significantly
> worse performance than the base algorithm (in particular, worse
> scalability).  All this did was add transaction conflicts in readers;
> this isn't an artificial special case, but can easily happen through
> things like false sharing.

Here are the results:
https://www.sourceware.org/ml/libc-alpha/2016-12/msg01100.html