Bug 11882

Summary: dbench 15% regression with 2.6.28-rc1
Product: Other Reporter: Rafael J. Wysocki (rjw)
Component: OtherAssignee: Peter Zijlstra (a.p.zijlstra)
Status: CLOSED CODE_FIX    
Severity: normal CC: mingo, yanmin_zhang
Priority: P1    
Hardware: All   
OS: Linux   
Kernel Version: 2.6.28-rc1 Subsystem:
Regression: Yes Bisected commit-id:
Bug Depends on:    
Bug Blocks: 11808    

Description Rafael J. Wysocki 2008-10-28 16:19:33 UTC 
Subject    : dbench 15% regression with 2.6.28-rc1
Submitter  : "Zhang, Yanmin" <yanmin_zhang@linux.intel.com>
Date       : 2008-10-28 8:41
References : http://marc.info/?l=linux-kernel&m=122518333103345&w=4

This entry is being used for tracking a regression from 2.6.27.  Please don't
close it until the problem is fixed in the mainline.
Comment 1 Rafael J. Wysocki 2008-10-31 15:01:45 UTC 
Caused by:

commit 695698500912c4479ddf4723e492de3970ff8530
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date:   Tue Sep 23 14:54:23 2008 +0200

    sched: rework wakeup preemption

    Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
Comment 2 Peter Zijlstra 2008-10-31 15:20:15 UTC 
On Fri, 2008-10-31 at 15:01 -0700, bugme-daemon@bugzilla.kernel.org
wrote:

> ------- Comment #1 from rjw@sisk.pl  2008-10-31 15:01 -------
> Caused by:
> 
> commit 695698500912c4479ddf4723e492de3970ff8530
> Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
> Date:   Tue Sep 23 14:54:23 2008 +0200
> 
>     sched: rework wakeup preemption
> 
>     Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
>     Signed-off-by: Ingo Molnar <mingo@elte.hu>

Basically reverted by:

commit 464b75273f64be7c81fee975bd6ca9593df3427b
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date:   Fri Oct 24 11:06:15 2008 +0200

    sched: re-instate vruntime based wakeup preemption

    The advantage is that vruntime based wakeup preemption has a better
    conceptual model. Here wakeup_gran = 0 means: preempt when 'fair'.
    Therefore wakeup_gran is the granularity of unfairness we allow in order
    to make progress.

    Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Acked-by: Mike Galbraith <efault@gmx.de>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>

Which is already in -git
Comment 3 Yanmin Zhang 2008-11-03 17:26:26 UTC 
I confirm 2.6.28-rc3 fixes it.