--- In Firebird-Architect@yahoogroups.com, Jim Starkey <jas@n...>
wrote:

> A second question is performance tradeoffs. The easy what to make

a

> rwlock class is to use a mutex to control access to the

synchronization

> object, making an uncontested lock more expensive than a mutex.

The Sun

> rwlock mechanism has this performance characteristic, though I

can't say

> this is their implementation. The alternative is a homebrew using
> whatever interlock ingredients available on the platform (more on

that

> later). An rwlock mechanism optimized for database trades off

speed of

> uncontested locks for a higher overhead for contested locks. I

know of

> no generally available rwlock mechanism with both monitor semantics

and

> fast lock performance, though there may be some. Anyone? Anyone?

I'm not an expert in the area, but this IBM researcher perhaps has
the answers you are looking for:
http://www.research.ibm.com/people/d/dfb/talks/Bacon97FeatherweightTal
k.pdf
and
http://www.research.ibm.com/people/d/dfb/papers/Bacon98Thin.pdf

Paul