On Mon, Jul 10, 2017 at 07:46:09AM -0700, Andi Kleen wrote: > > So how much of the gain is simply due to skipping NOHZ? Mike used to > > carry a patch that would throttle NOHZ. And that is a _far_ smaller and > > simpler patch to do. > > Have you ever looked at a ftrace or PT trace of the idle entry? > > There's just too much stuff going on there. NOHZ is just the tip > of the iceberg.
I have, and last time I did the actual poking at the LAPIC (to make NOHZ happen) was by far the slowest thing happening. Data to indicate what hurts how much would be a very good addition to the Changelogs. Clearly you have some, you really should have shared.
