On 12/03/2020 09:48, Alan Cox wrote: > Just to be clear, this is not just a matter of whether our release fences are > poorly or inefficiently implemented. Release fences (as defined by the C/C++ > standards that inspire our atomics) have *different* semantics than release > stores. Specifically, a release fence places more ordering restrictions on the > nearby store accesses than a release store does. (In fact, "man 9 atomic" > describes this.) Thus, it is almost inevitable that a release fence will > have a > higher cost than the best possible implementation of a release store.
For people like me who are new to these things here is a good explanation (perhaps a bad title, though): https://preshing.com/20131125/acquire-and-release-fences-dont-work-the-way-youd-expect/ -- Andriy Gapon _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
