Re: [RFC] KVM guest page swap out support - take2

[Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

Shaohua Li wrote:
> Hi,
> This is a updated patch set of swap out kvm guest pages.Changes are:
> 1. refresh against to kvm-26
> 2. clean up shadow page handling to make gfn_to_page not be called
> within kmap_atomic/kunamp_atomic.
> 3. variant bug fixing. Now the patch is quite stable in my test.
> 4. make swap out optional. A compile option can completely close swap
> out. There should be no performance impact if swapout isn't enabled.
>   

What is the performance impact if swapout is enabled, but there is no 
memory pressure?  I prefer to have this enabled unconditionally (well, 
dependent on CONFIG_SWAP), but have a tunable to control the swapper 
aggressiveness (like /proc/sys/vm/swappiness).


> There are still a lot of unresolved issues:
> 1. just work for one vm. waiting for kvm hook into scheduler
>   

I will implement this soon.

> 2. Not work for mp guest and can't swap out pages which shadow page
> table point to, this require kvm .flush_tlb can send ipi to vcpu.
>   

This, too, will be added soon.  This is part of the apic patchset.

> 3. swapoff isn't supported. We need a hook to sys_swapoff for kvm.
>
> Please review, suggests and comments are welcome.
>   

I'll review it later today.  Meanwhile, it would help if the patches 
were posted inline instead of in a tarball.

I'm also interested in what the s390 folk have to say.

-- 
error compiling committee.c: too many arguments to function


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