Re: Dynamically allocated locks

[Jason Thorpe <thorpej%shagadelic.org@localhost>]

On Mar 25, 2008, at 1:04 PM, jonathan%dsg.stanford.edu@localhost wrote:
> In message <FA2A84E8-8919-42A8-883C-A6658DCC3FE6%shagadelic.org@localhost>,
> Jason Thorpe writes:
>
> > On Mar 24, 2008, at 10:10 AM, Matt Thomas wrote:
> >
> > > Yes.  One / cacheline size is a dramatic waste of space.  Some
> > > systems have
> > > 128 bytes per cacheline.  On systems with small caches or UP systems
> > > it's
> > > extremely expensive.
> >
> > Two independent locks in a single cache line is guaranteed to  
> > crease a
> > false-sharing situation.  It is best avoided, even if cache pressure
> > is the trade-off.
>
> Even on a UP system?  In the kernel? Surely not.

Obviously on a UP system, it doesn't matter, and Andy already  
suggested that he would change the code to account for that.

-- thorpej