Re: [PATCH 15/45] xfs: CIL work is serialised, not pipelined

Andi Kleen
2021-03-09T22:36:23Z

"Darrick J. Wong" <djwong@kernel.org> 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