Bug 14383

Summary: hackbench regression with kernel 2.6.32-rc1
Product: Process Management Reporter: Rafael J. Wysocki (rjw)
Component: SchedulerAssignee: Ingo Molnar (mingo)
Status: CLOSED CODE_FIX    
Severity: normal CC: yanmin_zhang
Priority: P1    
Hardware: All   
OS: Linux   
Kernel Version: 2.6.32-rc1 Subsystem:
Regression: Yes Bisected commit-id:
Bug Depends on:    
Bug Blocks: 14230    

Description Rafael J. Wysocki 2009-10-11 21:13:13 UTC 
Subject    : hackbench regression with kernel 2.6.32-rc1
Submitter  : "Zhang, Yanmin" <yanmin_zhang@linux.intel.com>
Date       : 2009-10-09 9:19
References : http://marc.info/?l=linux-kernel&m=125508007510274&w=4
Handled-By : Peter Zijlstra <a.p.zijlstra@chello.nl>

This entry is being used for tracking a regression from 2.6.31.  Please don't
close it until the problem is fixed in the mainline.

Caused by:

commit 29cd8bae396583a2ee9a3340db8c5102acf9f6fd
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date:   Thu Sep 17 09:01:14 2009 +0200

    sched: Fix SD_POWERSAVING_BALANCE|SD_PREFER_LOCAL vs SD_WAKE_AFFINE

and 

commit de69a80be32445b0a71e8e3b757e584d7beb90f7
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date:   Thu Sep 17 09:01:20 2009 +0200

    sched: Stop buddies from hogging the system
Comment 1 Rafael J. Wysocki 2009-10-11 21:13:46 UTC 
First-Bad-Commit : 29cd8bae396583a2ee9a3340db8c5102acf9f6fd
Comment 2 Yanmin Zhang 2009-11-23 00:51:26 UTC 
On core2 arch machines, hackbench regression disappears and there is much
improvement instead of regression. 
On Nehalem machine, no big change, comparing with 2.6.31.

On Itanium machines (2 sockets or 4 sockets), the regression become
about 20%. Originally it's 70%.

I think we could close the bug report now. I might continue to investigate the regression on Itanium machine.
Comment 3 Rafael J. Wysocki 2009-11-23 19:15:43 UTC 
Closing.