Re: [Qemu-devel] linux guests and ksm performance

[address@hidden]

Stefan Hajnoczi <address@hidden> schrieb:

>On Thu, Feb 23, 2012 at 3:40 PM, Peter Lieven <address@hidden> wrote:
>> However, in a virtual machine I have not observed the above slow down
>to
>> that extend
>> while the benefit of zero after free in a virtualisation environment
>is
>> obvious:
>>
>> 1) zero pages can easily be merged by ksm or other technique.
>> 2) zero (dup) pages are a lot faster to transfer in case of
>migration.
>
>The other approach is a memory page "discard" mechanism - which
>obviously requires more code changes than zeroing freed pages.
>
>The advantage is that we don't take the brute-force and CPU intensive
>approach of zeroing pages.  It would be like a fine-grained ballooning
>feature.
>

I dont think that it is cpu intense. All user pages are zeroed anyway, but at 
allocation time it shouldnt be a big difference in terms of cpu power.

>I hope someone will follow up saying this has already been done or
>prototyped :).
>
>Stefan

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