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From: Andrew Gallatin <gallatin@cs.duke.edu>
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Date: Mon, 6 Feb 2006 14:46:36 -0500 (EST)
To: Andre Oppermann <andre@freebsd.org>
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Subject: Re: machdep.cpu_idle_hlt and SMP perf?
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Andre Oppermann writes:
 > Andrew Gallatin wrote:
 > > Why dooes machdep.cpu_idle_hlt=1 drop my 10GbE network rx
 > > performance by a considerable amount (7.5Gbs -> 5.5Gbs)?

<...>

 > This may be the same problem OpenBSD has fixed last year in the handling
 > of the idle loop.  From the kerneltrap posting:

<....>

 > First commit message:
 >   http://marc.theaimsgroup.com/?l=openbsd-cvs&m=111692513727274&w=2
 > 
 > The MFC with all changes in one commit message:
 >   http://marc.theaimsgroup.com/?l=openbsd-cvs&m=111859519015510&w=2

The bug they fixes was missing interrupts by both calling APM's idle
routine, which may hlt, and hlt'ing in the idle loop itself.  Since I
have no idea what acpi is doing, I got excited about this.

Alas, it seems like this isn't it.  I pointed cpu_idle_hook back to
cpu_idle_default and away from acpi_cpu_idle, but that made no
difference.

Drew