Messages in this thread | | | Date | Tue, 11 Jul 2017 11:02:40 +0200 | From | Peter Zijlstra <> | Subject | Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods |
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On Mon, Jul 10, 2017 at 10:27:05AM -0700, Andi Kleen wrote: > On Mon, Jul 10, 2017 at 06:42:06PM +0200, Peter Zijlstra wrote:
> > I have, and last time I did the actual poking at the LAPIC (to make NOHZ > > happen) was by far the slowest thing happening. > > That must have been a long time ago because modern systems use TSC deadline > for a very long time ...
Its been a while, but I didn't use the very latest chip when I did.
> It's still slow, but not as slow as the LAPIC.
Deadline TSC is a LAPIC timer mode. Sure the MSR might be slightly cheaper than the MMIO, but its still painful.
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