"Darrick J. Wong" <djwong@xxxxxxxxxx> writes: > It might be nice to leave that as a breadcrumb, then, in case the > spinlock scalability problems ever get solved. It might be already solved, depending on if Dave's rule of thumb was determined before the Linux spinlocks switched to MCS locks or not. In my experience spinlock scalability depends a lot on how long the critical section is (that is very important, short sections are a lot worse than long sections), as well as if the contention is inside a socket or over sockets, and the actual hardware behaves differently too. So I would be quite surprised if the "rule of 4" generally holds. -Andi
