Bug 127871

Summary:	voluntary preemption patch is not completely included
Product:	[Fedora] Fedora	Reporter:	Hans Ecke <hansecke>
Component:	kernel	Assignee:	Arjan van de Ven <arjanv>
Status:	CLOSED NOTABUG	QA Contact:	Brian Brock <bbrock>
Severity:	low	Docs Contact:
Priority:	medium
Version:	rawhide	CC:	wtogami
Target Milestone:	---
Target Release:	---
Hardware:	i386
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2004-07-15 17:48:26 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Hans Ecke 2004-07-14 20:39:57 UTC

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Description of problem:
In short: the version of voluntary preemption included in the latest  testing kernels misses features from the upstream version from Ingo Molnar. This is
   * voluntary and involuntary preemption can not be enabled at the same time
   * status of neither can be set in /proc/sys/kernel

++++++++++++++++++++++++++++++++

After reading the article about voluntary preemption at
   http://kerneltrap.org/node/view/3440
I wanted to try it out. Since Arjan's kernels from
   http://people.redhat.com/arjanv/2.6/
say that they include voluntary preemption, I downloaded kernel-sourcecode-2.6.7-1.486 and compiled a new kernel from that. (I need my own kernel for read access to NTFS, but that is the only difference to his default kernel)

Compiling the kernel showed the first difference to the article: PREEMPT and PREEMPT_VOLUNTARY can not be set at the same time.

Afer rebooting I wanted to see what /proc/sys/kernel/voluntary_preemption and /proc/sys/kernel/kernel_preemption say. But neither are available.

Looking through patches 1080, 1081, 1082 (from kernel-2.6.7-1.486.src.rpm) it becomes apparent that this version of voluntary preempt is quite a bit different from the one presented at
   http://people.redhat.com/mingo/voluntary-preempt

Is there a reason for that?



Version-Release number of selected component (if applicable):
kernel-(sourcecode-)2.6.7-1.486

How reproducible:
Always

Steps to Reproduce:
1.download kernel-2.6.7-1.486.src.rpm
2.rpm -i <file.src.rpm>
3.look at linux-2.6.7-voluntary-preemption.patch, linux-2.6.7-early-schedule.patch, linux-2.6.7-might_sleep.patch in /usr/src/redhat/SOURCES

    

Actual Results:  * when recompiling, PREEMPT and PREEMPT_VOLUNTARY can not be set at the same time
* knobs in /proc/sys/kernel are missing

Expected Results:  * when recompiling, PREEMPT and PREEMPT_VOLUNTARY should both be settable
* knobs in /proc/sys/kernel are available

Additional info:

This is not so much a bugreport as a request for comment: why did you cut those features out?

Comment 1 Arjan van de Ven 2004-07-15 07:57:39 UTC

the proc knobs in Ingo's patch were only temporary (as per his
announcement); the patch in the kernel rpm is closer to the final
form, eg it is always on and far less invasive to the kernel.

Comment 2 Hans Ecke 2004-07-15 17:48:26 UTC

Thanks for the information.