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Re: [Qemu-devel] [PATCH kernel v4 7/7] virtio-balloon: tell host vm's un
From: |
Dave Hansen |
Subject: |
Re: [Qemu-devel] [PATCH kernel v4 7/7] virtio-balloon: tell host vm's unused page info |
Date: |
Tue, 8 Nov 2016 10:30:30 -0800 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.3.0 |
On 11/07/2016 09:50 PM, Li, Liang Z wrote:
> Sounds good. Should we ignore some of the order-0 pages in step 4 if the
> bitmap is full?
> Or should retry to get a complete list of order-0 pages?
I think that's a pretty reasonable thing to do.
>>> It seems the benefit we get for this feature is not as big as that in fast
>> balloon inflating/deflating.
>>>>
>>>> You should not be using get_max_pfn(). Any patch set that continues
>>>> to use it is not likely to be using a proper algorithm.
>>>
>>> Do you have any suggestion about how to avoid it?
>>
>> Yes: get the pfns from the page free lists alone. Don't derive
>> them from the pfn limits of the system or zones.
>
> The ' get_max_pfn()' can be avoid in this patch, but I think we can't
> avoid it completely. We need it as a hint for allocating a proper
> size bitmap. No?
If you start with higher-order pages, you'll be unlikely to get anywhere
close to filling up a bitmap that was sized to hold all possible order-0
pages on the system. Any use of max_pfn also means that you'll
completely mis-size bitmaps on sparse systems with large holes.
I think you should size it based on the size of the free lists, if anything.
- [Qemu-devel] [PATCH kernel v4 3/7] mm: add a function to get the max pfn, (continued)
- [Qemu-devel] [PATCH kernel v4 3/7] mm: add a function to get the max pfn, Liang Li, 2016/11/02
- [Qemu-devel] [PATCH kernel v4 2/7] virtio-balloon: define new feature bit and head struct, Liang Li, 2016/11/02
- [Qemu-devel] [PATCH kernel v4 4/7] virtio-balloon: speed up inflate/deflate process, Liang Li, 2016/11/02
- [Qemu-devel] [PATCH kernel v4 6/7] virtio-balloon: define flags and head for host request vq, Liang Li, 2016/11/02
- [Qemu-devel] [PATCH kernel v4 5/7] mm: add the related functions to get unused page, Liang Li, 2016/11/02
- [Qemu-devel] [PATCH kernel v4 7/7] virtio-balloon: tell host vm's unused page info, Liang Li, 2016/11/02