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    SubjectRe: [PATCH 0/3] sched: newidle and RT wake-buddy fixes
    >>> On Mon, Jun 30, 2008 at  9:15 AM, in message <20080630131511.GA7506@elte.hu>,
    Ingo Molnar <mingo@elte.hu> wrote:

    > * Gregory Haskins <ghaskins@novell.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:

    Ok, I dug in a little bit here. I haven't verified this out yet, but I think the problem is that
    your config is PREEMPT_VOLUNTARY which NOPs the preempt_disable() in schedule() that
    I rely on to allow the lock to be dropped. (Doh!)

    One way I can fix this is to fixup the newidle() code to only play the irq dropping tricks
    ifdef CONFIG_PREEMPT == TRUE. Does this sound reasonable, or is there a better way
    to address this?

    -Greg

    >
    > Linux version 2.6.26-rc8-tip (mingo@dione) (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@novell.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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