On Fri, Jul 04, 2014 at 07:21:15AM -0700, Jarno Rajahalme wrote: > Use explicit variants of atomic operations for the ovs_refcount to > avoid the overhead of the default memory_order_seq_cst. > > Adding a reference requires no memory ordering, as the calling thread > is already assumed to have protected access to the object being > reference counted. Hence, memory_order_relaxed is used for > ovs_refcount_ref(). ovs_refcount_read() does not change the reference > count, so it can also use memory_order_relaxed. > > Unreferencing an object needs a release barrier, so that none of the > accesses to the protected object are reordered after the atomic > decrement operation. Additionally, an explicit acquire barrier is > needed before the object is recycled, to keep the subsequent accesses > to the object's memory from being reordered before the atomic > decrement operation. > > This patch follows the memory ordering and argumentation discussed > here: > > http://www.chaoticmind.net/~hcb/projects/boost.atomic/doc/atomic/usage_examples.html > > Signed-off-by: Jarno Rajahalme <jrajaha...@nicira.com>
Acked-by: Ben Pfaff <b...@nicira.com> _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
