On Mon, 3 Dec 2012, Mel Gorman wrote: > On Fri, Nov 30, 2012 at 12:37:49PM -0800, Linus Torvalds wrote: > > So if this is a migration-specific scalability issue, then it might be > > possible to solve by making the mutex be a rwsem instead, and have > > migration only take it for reading. > > > > Of course, I'm quite possibly wrong, and the code depends on full > > mutual exclusion. > > > > Just a thought, in case it makes somebody go "Hmm.." > > > > Offhand, I cannot think of a reason why a rwsem would not work. This > thing originally became a mutex because the RT people (Peter in > particular) cared about being able to preempt faster. It'd be nice if > they confirmed that rwsem is not be a problem for them. rwsems are preemptable as well. So I don't think this was Peter's main concern. If it works with an rwsem, then go ahead. rwsems degrade on RT because we cannot do multiple reader boosting, so they allow only a single reader which can take it recursive. But that's an RT specific issue and nothing you should worry about. Thanks, tglx -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>