[PATCH] Convert the VFS cache lock to an rmlock

[Ryan Stone]

On Thu, Mar 12, 2015 at 12:37 PM, Adrian Chadd <adrian at freebsd.org> wrote:
> Do you have access to any boxes that have more than 12 cores?

I have a 14-core hyperthreaded machine (so 28 logical cores), but it has no
disk (long story).  I could do a build out of a memory disk though.

Also, to ask a stupid question - why wasn't the reader gifted a
> temporary priority boost because you were trying to acquire the write
> lock?
>

rwlocks don't have any metadata tracking what threads hold a read lock, so
it's impossible to propagate priority to them.  rwlocks only keep a counter
of the number of readers.