linux-kernel - Re: [PATCH 1/2] VMware guest detection for x86 and x86-64

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Message-ID: <48DA8402.1090701@zytor.com>
Date:	Wed, 24 Sep 2008 11:16:34 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	cristi.magherusan@....utcluj.ro
CC:	Yan Li <elliot.li.tech@...il.com>, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...e.hu>, joerg.roedel@....com,
	rjmaomao@...il.com, Yinghai Lu <yhlu.kernel@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>, nancydreaming@...il.com
Subject: Re: [PATCH 1/2] VMware guest detection for x86 and x86-64

Cristi Magherusan wrote:
> On Wed, 2008-09-24 at 22:23 +0800, Yan Li wrote: 
>> On Wed, Sep 24, 2008 at 05:10:24PM +0300, Cristi Magherusan wrote:
>>> On Wed, 2008-09-24 at 20:22 +0800, Yan Li wrote:
>>>> Detects whether we are running as a VMware guest or not. Detection is
>>>> based upon DMI vendor string.
>>>>
>>>> It provides a function:
>>>> int is_vmware_guest(void)
>>>> that can be used easily to detect if we are running as a VMware guest
>>>> or not.
>>> We can also use this feature to force the HZ value to 100 or 250 at most
>>> when running in a virtual environment, since VirtualBox had some issues
>>> with this by taking a lot of CPU time when the HZ was set to 1000.
>> That's good. But this function is used for detecting VMware guest
>> only.  Do you think VMware also suffers from this problem?
>>
> I don't know for sure about VMware, but someone who has it installed can
> try it. I had this issue with a CentOS 5-server virtual machine
> downloaded from http://www.thoughtpolice.co.uk/vmware/
> 
> The fix consisted in using a kernel compiled with the HZ value set to
> 100 instead of the default which was 1000.
> 

HZ is a compile-time constant, though.  Changing that would require 
adding a bunch of general divides, at the very least.

	-hpa
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