Re: [PATCH 00/13] KVM: MMU: fast page fault

Takuya Yoshikawa
2012-04-13T14:25:38Z

Xiao,

Takuya Yoshikawa <takuya.yoshikawa@gmail.com> wrote:

> > What is your really want to say but i missed?
>
> How to improve and what we should pay for that.
>
> Note that I am not objecting to O(1) itself.
>

I forgot to say one important thing -- I might give you wrong impression.

I am perfectly fine with your lock-less work. It is really nice!

The reason I say much about O(1) is that O(1) and rmap based
GET_DIRTY_LOG have fundamentally different characteristics.

I am thinking really seriously how to make dirty page tracking work
well with QEMU in the future.

For example, I am thinking about multi-threaded and fine-grained
GET_DIRTY_LOG.

If we use rmap based GET_DIRTY_LOG, we can restrict write protection to
only a selected area of one guest memory slot.

So we may be able to make each thread process dirty pages independently
from other threads by calling GET_DIRTY_LOG for its own area.

But I know that O(1) has its own good point.
So please wait a bit. I will write up what I am thinking or send patches.

Anyway, I am looking forward to your lock-less work!
It will improve the current GET_DIRTY_LOG performance.

Thanks,
Takuya