RFC: setting performance_cx_lowest=C2 in -HEAD to avoid lock contention on many-CPU boxes

[Adrian Chadd]

On 25 April 2015 at 10:18, K. Macy <kmacy at freebsd.org> wrote:
> Perhaps use an arbitrary cutoff - say <= 8 cores - where the
> cx_lowest=C3. This serialization isn't going to hurt on systems with
> more modest core counts.

Maybe. I bet it's a function of the idle state entry rate and core
count - so maybe at 8 cores it'll hurt but only if it's entering idle
at a high rate. Eg, if it's taking a hell of a lot of interrupts but
not maxing out the CPU.




-adrian