Switch pfil(9) to rmlocks

[Alfred Perlstein]

* Robert Watson <rwatson at FreeBSD.org> [071126 12:37] wrote:
> 
> On Fri, 23 Nov 2007, Max Laier wrote:
> 
> >attached is a diff to switch the pfil(9) subsystem to rmlocks, which are 
> >more suited for the task.  I'd like some exposure before doing the switch, 
> >but I don't expect any fallout.  This email is going through the patched 
> >pfil already - twice.
> 
> FYI, since people are experimenting with rmlocks as a substitute for 
> rwlocks, I played with moving the global rwlock used to protect the name 
> space and linkage of UNIX domain sockets to be an rmlock.  Kris didn't see 
> any measurable change in performance for his MySQL benchmarks, but I 
> figured I'd post the patches as they give a sense of what change impact 
> things like reader state management have on code.  Attached below.  I have 
> no current plans to commit these changes as they appear not to offer 
> benefit (either because the rwlock overhead was negigible compared to other 
> costs in the benchmark, or because the read/write blend was too scewed 
> towards writes -- I think probably the former rather than the latter).

I would track the read/write lock mix to get an idea of what the
ratio is.

-Alfred