linux-kernel - Re: [PATCH 0/3] sched: newidle and RT wake-buddy fixes

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Date:	Mon, 30 Jun 2008 15:15:11 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Gregory Haskins <ghaskins@...ell.com>
Cc:	peterz@...radead.org, npiggin@...e.de, rostedt@...dmis.org,
	linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org
Subject: Re: [PATCH 0/3] sched: newidle and RT wake-buddy fixes


* Gregory Haskins <ghaskins@...ell.com> wrote:

> Hi Ingo,
>   The following patches apply to linux-tip/sched/devel and enhance the
> performance of the kernel (specifically in PREEMPT_RT, though they do
> not regress mainline performance as far as I can tell).  They offer
> somewhere between 50-100% speedups in netperf performance, depending
> on the test.

-tip testing found this boot hang:

 Linux version 2.6.26-rc8-tip (mingo@...ne) (gcc version 4.2.3) #12917 
 SMP Mon Jun 30 15:06:32 CEST 2008
 [...]
 CPU 1/1 -> Node 0
 CPU: Physical Processor ID: 0
 CPU: Processor Core ID: 1
 CPU1: AMD Athlon(tm) 64 X2 Dual Core Processor 3800+ stepping 02
 Brought up 2 CPUs
 Total of 2 processors activated (8041.15 BogoMIPS).
 [ hard hang ]

with this config:

  http://redhat.com/~mingo/misc/config-Mon_Jun_30_14_54_19_CEST_2008.bad

full bootlog:

  http://redhat.com/~mingo/misc/hang-Mon_Jun_30_14_54_19_CEST_2008.bad

it should continue with this bootup sequence:

  calling  net_ns_init+0x0/0x1a0
  net_namespace: 376 bytes
  initcall net_ns_init+0x0/0x1a0 returned 0 after 0 msecs
  calling  init_smp_flush+0x0/0x60

i've bisected it down to:

--------------
| commit cc8160c56843201891766660e3816d2e546c1b17
| Author: Gregory Haskins <ghaskins@...ell.com>
| Date:   Fri Jun 27 14:29:50 2008 -0600
|
|     sched: enable interrupts and drop rq-lock during newidle balancing
--------------

so i've reverted that change for now.

	Ingo
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