|
xen-devel
RE: Re: [Xen-devel] Balloon driver for Linux/HVM
FYI, Transcendent Memory does work with HVM, with a recent Xen
and the proper Linux guest-side patches (including Stefano’s PV-on-HVM
patchset). There is extra overhead in an HVM for each tmem call due to
vmenter/vmexit and I have not measured performance, but this overhead should
not be too large on newer processors. Also, of course, Transcendent
Memory will not work with Windows guests (or any guests that do not have tmem
patches), while PoD is primarily intended to work with Windows (because, IIRC,
Windows zeroes all of memory).
I agree that guest IO cacheing is mostly useless for CLEAN pages
if the dom0 page cache is large enough for all guests (or if tmem is working).
For dirty pages, using dom0 cacheing risks data integrity problems (e.g. the
guest believes a transaction to disk is complete but the data is in a dom0
cache that has not been flushed to disk).
Dan
From: Chu Rui
[mailto:ruichu@xxxxxxxxx]
Sent: Tuesday, November 16, 2010 8:37 AM
To: George Dunlap; Xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: Re: Re: [Xen-devel] Balloon driver for Linux/HVM
Thank you for your kind reply, George.
I am interested on the PoD memory. In my perspective, PoD
mainly works in the system initialization stage. Before the balloon driver
begins to work, it can limit the memory consumption of the guests.
However, after a while the guest OS will commit more memory, but PoD cannot
reclaim any more at that time even when the committed pages is IO cache. While
the balloon keeps work all of the time.
Would you please tell me whether my thought is correct?
Actually, in my opinion, the guest IO cache is
mostly useless, since the Dom0 will cache the IO operations. Such a
double-cache wastes the memory resources. Is there any good idea for that like
Transcendent Memory while works with HVM?
在 2010年11月16日 下午8:56，George
Dunlap <dunlapg@xxxxxxxxx>写道：
2010/11/16 牛立新 <topperxin@xxxxxxx>:
> o, it's strange, the old
version have no this limitation.
No; unfortunately a great deal of functionality present in
"classic
xen" has been lost in the process of getting the core dom0 support
into the pvops kernel. I think the plan is, once we have the
necessary changes to non-xen code pushed up stream, we can start
working on getting feature parity with classic xen.
>
>
> At 2010-11-16 19:35:50，"Stefano
Stabellini" <stefano.stabellini@xxxxxxxxxxxxx>
wrote:
>
>>On Tue, 16 Nov 2010, Chu Rui wrote:
>>> Hi,
>>> I have noticed that, in the code of linux/drivers/xen/balloon.c,
there exists the snippet as this:
>>>
>>> static int __init balloon_init(void)
>>> {
>>> unsigned long pfn;
>>> struct page *page;
>>> if (!xen_pv_domain())
>>> return -ENODEV;
>>> .....
>>> }
>>>
>>> Does it means the driver will not work in HVM? If so, where is the
HVN-enabled code for that?
>>
>>not yet, even though I have a patch ready to enable it:
>>
>>git://xenbits.xen.org/people/sstabellini/linux-pvhvm.git
2.6.36-rc7-pvhvm-v1
>
>
> ________________________________
> 网易163/126邮箱百分百兼容iphone
ipad邮件收发
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-devel
>
>
|
_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel
|
|
|
Home