On Wed, Aug 15, 2012 at 12:25:28PM +0300, Michael S. Tsirkin wrote: > On Wed, Aug 15, 2012 at 10:05:28AM +0100, Mel Gorman wrote: > > On Tue, Aug 14, 2012 at 05:11:13PM -0300, Rafael Aquini wrote: > > > On Tue, Aug 14, 2012 at 10:51:39PM +0300, Michael S. Tsirkin wrote: > > > > What I think you should do is use rcu for access. > > > > And here sync rcu before freeing. > > > > Maybe an overkill but at least a documented synchronization > > > > primitive, and it is very light weight. > > > > > > > > > > I liked your suggestion on barriers, as well. > > > > > > > I have not thought about this as deeply as I shouold but is simply rechecking > > the mapping under the pages_lock to make sure the page is still a balloon > > page an option? i.e. use pages_lock to stabilise page->mapping. > > To clarify, are you concerned about cost of rcu_read_lock > for non balloon pages? > Not as such, but given the choice between introducing RCU locking and rechecking page->mapping under a spinlock I would choose the latter as it is more straight-forward. -- Mel Gorman SUSE Labs -- 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>