Date: Wed, 4 Jan 2006 19:17:47 -0500
From: Chuck Ebbert <76306.1226@compuserve.com>
Subject: Re: [patch 2.6.15] i386: Optimize local APIC timer interrupt
  code
To: Andrew Morton <akpm@osdl.org>
Cc: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>, torvalds@osdl.org,
       linux-kernel@vger.kernel.org
Message-ID: <200601041922_MC3-1-B554-CF6A@compuserve.com>
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In-Reply-To: <20060104150139.34829833.akpm@osdl.org>


Andrew Morton wrote:

> The code which you're patching is cheerfully nuked by a patch in Andi's
> tree:
> ftp://ftp.firstfloor.org/pub/ak/x86_64/quilt-current/patches/no-subjiffy-profile
>
> I don't immediately understand that patch and I don't recall seeing it
> discussed - maybe I was asleep.
>
> It removes the profile multiplier (readprofile -M).  I've used that
> occasionally, but can't say that I noticed much benefit from it.

 It's probably required for the i386-timer-broadcast patch from the same
patchset.  Apparently some Intel CPUs stop their local APIC timer when in
certain ACPI C-states, so that patch switches them to use an IPI broadcast
from the main timer interrupt instead.  Supporting subjiffy profiling
is impossible in that case, so the code was removed.

-- 
Chuck
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