Bug 11904

Summary:	upstream regression (IO-APIC?)
Product:	Platform Specific/Hardware	Reporter:	Rafael J. Wysocki (rjw)
Component:	i386	Assignee:	platform_i386
Status:	CLOSED INVALID
Severity:	normal	CC:	akataria, bzolnier
Priority:	P1
Hardware:	All
OS:	Linux
Kernel Version:	commit e946217e4fdaa67681bbabfa8e6b18641921f750	Subsystem:
Regression:	Yes	Bisected commit-id:
Bug Depends on:
Bug Blocks:	11167

Description Rafael J. Wysocki 2008-10-30 14:16:34 UTC

Subject    : upstream regression (IO-APIC?)
Submitter  : Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Date       : 2008-10-30 0:00
References : http://marc.info/?l=linux-kernel&m=122532510328618&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 2008-11-02 09:39:46 UTC

This apparently is a regression from 2.6.26.

Caused by:

commit 3da757daf86e498872855f0b5e101f763ba79499
Author: Alok Kataria <akataria@vmware.com>
Date:   Fri Jun 20 15:06:33 2008 -0700

    x86: use cpu_khz for loops_per_jiffy calculation

    Signed-off-by: Alok N Kataria <akataria@vmware.com>
    Cc: Arjan van de Ven <arjan@infradead.org>
    Cc: Daniel Hecht <dhecht@vmware.com>
    Cc: Tim Mann <mann@vmware.com>
    Cc: Zach Amsden <zach@vmware.com>
    Cc: Sahil Rihan <srihan@vmware.com>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>

Patch : http://marc.info/?l=linux-kernel&m=122563711522315&w=4

Comment 2 Alok Kataria 2008-11-03 17:06:57 UTC

(In reply to comment #1)
> This apparently is a regression from 2.6.26.
> 
> Caused by:
> 
> commit 3da757daf86e498872855f0b5e101f763ba79499
> Author: Alok Kataria <akataria@vmware.com>
> Date:   Fri Jun 20 15:06:33 2008 -0700
> 
>     x86: use cpu_khz for loops_per_jiffy calculation
> 

This is not a kernel bug, looks like a qemu, timing emulator bug.

http://lkml.org/lkml/2008/11/3/222

Bart mentions this on the thread,
==================
I now noticed that the problem happens only with HZ == 250 host
and HZ == 1000 guest.  When host and guest are using the same HZ setting
everything works fine.
==================

Rafael, will leave upto you to decide if we should close this bug.

Thanks,
Alok

Comment 3 Rafael J. Wysocki 2008-11-03 23:20:40 UTC

Let's close it, then.

Comment 4 Bartlomiej Zolnierkiewicz 2008-11-09 08:22:00 UTC

Yep, closing it is fine with me.

PS There is also some kind of workaround available with forcing CONFIG_HZ=250's lpj value using "lpj=" kernel option for CONFIG_HZ=1000 kernel.