Re: [RFC PATCH] introduce sys_membarrier(): process-wide memory barrier

Paul E. McKenney
2010-01-09T00:20:48Z

On Fri, Jan 08, 2010 at 06:53:38PM -0500, Mathieu Desnoyers wrote:
> * Steven Rostedt (rostedt@goodmis.org) wrote:
> > Well, if we just grab the task_rq(task)->lock here, then we should be
> > OK? We would guarantee that curr is either the task we want or not.
>
> Hrm, I just tested it, and there seems to be a significant performance
> penality involved with taking these locks for each CPU, even with just 8
> cores. So if we can do without the locks, that would be preferred.

How significant? Factor of two? Two orders of magnitude?

Thanx, Paul