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    SubjectRe: VolanoMark regression with 2.6.27-rc1
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    On Mon, 2008-08-18 at 10:51 +0530, Dhaval Giani wrote:
    > > > > > > So with kernel 2.6.27-rc1, the successful wakeup_affine is about
    > > > > > > double of the one of 2.6.27-rc1
    > > > > > > on domain 0, but about 10 times on domain 1. That means more tasks are
    > > > > > > woken up on waker cpus.
    > > > > > >
    > > > > > > Does that mean it doesn't follow cache-hot checking?
    > > > > >
    > > > > > I'm a bit puzzled, but you're right - I too noticed that volanomark is
    > > > > > _very_ sensitive to affine wakeups.
    > > > > >
    > > > > > I'll try and find what changed in that code for GROUP=n.
    > > > >
    > > > > hi Yanmin,
    > > > >
    > > > > I was wondering if you could send me your config and what sysctls you
    > > > > have set. I have not been able to reproduce the 2.6.26 -> 2.6.27-rc1
    > > > > GROUP=n regression.
    > > > Pls. see the attachment. As for sysctl, I just set /proc/sys/kernel/sched_compat_yield=1.
    > > >
    > > > I am wondering if the load balance causes the regression when group=n. I manually delete
    > > > all GROUP codes and do a diff against 26 and 27-rc1.
    > > >
    > >
    > > You can disable load balancing by being in uniprocessor mode.
    > >
    >
    > Hi,
    >
    > I can see this regression only with sched_compat_yield=1. Some numbers
    > though, I see a 5% regression with max_cpus=1 whereas close to 50% with
    > SMP on a 8 way.
    After reverting below patch, volanoMark regression becomes less than 2% with CONFIG_GROUP_SCHED=n
    on my 8-core stoakely. The improvement on 16-core tigerton is about 44%, but there is still about
    20% regression, comparing with 2.6.26_nogroup.


    commit 93b75217df39e6d75889cc6f8050343286aff4a5
    Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Date: Fri Jun 27 13:41:33 2008 +0200

    sched: disable source/target_load bias

    The bias given by source/target_load functions can be very large, disable
    it by default to get faster convergence.

    Signed-off-by: Peter Zijlstra <peterz@infradead.org>
    Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
    Cc: Mike Galbraith <efault@gmx.de>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>



    This patch adds a new feature LB_BIAS, but uses it with a NOT, so I lost it when I tested
    single sched feature one by one. That also explains why wake_affine and load_balance_newidle
    have more successful task pulling with kernel 2.6.27-rc, because MC and CPU domain's wake_idx
    is 1, so this patch has impact on them.

    Dhaval, could you test it on your 8-way machine?

    >
    > Peter do you have any patches already, which I can try?
    >
    > Thanks,



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