On Mon, 2014-07-21 at 21:34 -0400, Steven Rostedt wrote: > I was telling Robert that if futexes get optimistic spinning, he should > reconsider their use of userspace spinlocks in favor of this, because > I'm pretty sure that they will see a great improvement.
My (dated) experience with pgsql says you're likely right. Once upon a time, preempting a userspace spinlock owner caused pgsql to collapse into a quivering heap. The scheduler trying to hand the CPU back to a preempted task instead of selecting what was strictly speaking the most deserving task afterward (LAST_BUDDY) let pgsql+oltp scale nice and flat instead of self destructing, but the root cause of collapse was spinners lacking knowledge. With spin done in kernel, you can know when spinning is a waste of perfectly good cycles. -Mike -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
