linux-kernel - Re: [Xen-devel] [patch 30/44] xen: Add support for preemption

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Message-ID: <47281C75.4040106@sina.com.cn>
Date:	Wed, 31 Oct 2007 14:11:01 +0800
From:	tgh <wwwwww4187@...a.com.cn>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
CC:	Xen-devel <xen-devel@...ts.xensource.com>,
	Jeremy Fitzhardinge <jeremy@...source.com>,
	Andi Kleen <ak@...e.de>, lkml <linux-kernel@...r.kernel.org>,
	Chris Wright <chrisw@...s-sol.org>,
	Andrew Morton <akpm@...ux-foundation.com>
Subject: Re: [Xen-devel] [patch 30/44] xen: Add support for preemption

Thank you for your reply
and what about the kernel thread in the xen hypervisor,are there some
instance of kernel threads running in the hypervisor?
I am not sure ,but somewhere I read that there is no kernel thread in
the xen hypervisor ,is it true or what about it?

Thanks in advance


Jeremy Fitzhardinge 写道:
> tgh wrote:
>   
>> Thank for your reply
>> and I still have several questions
>>   
>>     
>>> Yes, that's the normal mode of operation. The hypervisor will timeslice
>>> multiple vcpus onto a single vcpu.
>>>   
>>>     
>>>       
>> that is ,the VM could be preempted by xen,and could xen hypervisor also
>> be preempted to reschedule other vm or xen kernel thread?and are there
>> the counterpart abstractions in xen for kernel thread in linux?
>>   
>>     
>
> Yes, a vcpu in Xen is the same as a task in the kernel. In the same way
> the kernel multiplexes multiple tasks onto your cpu(s), Xen multiplexes
> multiple vcpus onto your cpu(s). This isn't directly visible to the
> guest kernel, in the same way that user processes can't generally
> observe timeslicing.
>
>   
>>> This patch doesn't relate to that; it's whether a Xen Linux guest's
>>> kernel can be preempted to reschedule processes while running under Xen.
>>>   
>>>     
>>>       
>> that is ,the patch makes the guest's kernel, rather than xen, be able to
>> be preempted ,is it right?
>>   
>>     
>
> Yes. Previous to that change, kernel preemption was disabled when
> compiling Xen support in.
>
> J
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@...ts.xensource.com
> http://lists.xensource.com/xen-devel
>
>
>   

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