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Re: [Qemu-devel] post-copy is broken?
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] post-copy is broken? |
Date: |
Thu, 14 Apr 2016 13:34:41 +0100 |
User-agent: |
Mutt/1.5.24 (2015-08-30) |
* Andrea Arcangeli (address@hidden) wrote:
> The next suspect is the massive THP refcounting change that went
> upstream recently:
> As further debug hint, can you try to disable THP and see if that
> makes the problem go away?
Yep, this seems to be the problem (cc'ing in Kirill).
122afea9626ab3f717b250a8dd3d5ebf57cdb56c - works (just before Kirill disables
THP)
61f5d698cc97600e813ca5cf8e449b1ea1c11492 - breaks (when THP is reenabled)
It's pretty reliable; as you say disabling THP makes it work again
and putting it back to THP/madvise mode makes it break. And you need
to test on a machine with some free ram to make sure THP has a chance
to have happened.
I'm not sure of all of the rework that happened in that series,
but my reading of it is that splitting of THP pages gets deferred;
so I wonder if when I do the madvise to turn THP off, if it's actually
still got THP pages and thus we end up with a whole THP mapped
when I'm expecting to be userfaulting those pages.
Dave
>
> Thanks,
> Andrea
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK
- [Qemu-devel] post-copy is broken?, Li, Liang Z, 2016/04/12
- Re: [Qemu-devel] post-copy is broken?, Dr. David Alan Gilbert, 2016/04/12
- Re: [Qemu-devel] post-copy is broken?, Dr. David Alan Gilbert, 2016/04/12
- Re: [Qemu-devel] post-copy is broken?, Li, Liang Z, 2016/04/12
- Re: [Qemu-devel] post-copy is broken?, Li, Liang Z, 2016/04/12
- Re: [Qemu-devel] post-copy is broken?, Dr. David Alan Gilbert, 2016/04/13
- Re: [Qemu-devel] post-copy is broken?, Dr. David Alan Gilbert, 2016/04/13
- Re: [Qemu-devel] post-copy is broken?, Dr. David Alan Gilbert, 2016/04/13
- Re: [Qemu-devel] post-copy is broken?, Andrea Arcangeli, 2016/04/13
- Re: [Qemu-devel] post-copy is broken?, Dr. David Alan Gilbert, 2016/04/14
- Re: [Qemu-devel] post-copy is broken?,
Dr. David Alan Gilbert <=
- Re: [Qemu-devel] post-copy is broken?, Andrea Arcangeli, 2016/04/14
- Re: [Qemu-devel] post-copy is broken?, Kirill A. Shutemov, 2016/04/15
- Re: [Qemu-devel] post-copy is broken?, Dr. David Alan Gilbert, 2016/04/15
- Re: [Qemu-devel] post-copy is broken?, Kirill A. Shutemov, 2016/04/15
- Re: [Qemu-devel] post-copy is broken?, Dr. David Alan Gilbert, 2016/04/15
- Re: [Qemu-devel] post-copy is broken?, Li, Liang Z, 2016/04/18
- Re: [Qemu-devel] post-copy is broken?, Dr. David Alan Gilbert, 2016/04/18
- Re: [Qemu-devel] post-copy is broken?, Li, Liang Z, 2016/04/18
- Re: [Qemu-devel] post-copy is broken?, Dr. David Alan Gilbert, 2016/04/18
- Re: [Qemu-devel] post-copy is broken?, Li, Liang Z, 2016/04/18