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| From: | Avi Kivity |
| Subject: | Re: [Qemu-devel] Re: [Qemu-commits] [COMMIT 3086844] Instead of writing a zero page, madvise it away |
| Date: | Mon, 22 Jun 2009 21:01:53 +0300 |
| User-agent: | Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1b3pre) Gecko/20090513 Fedora/3.0-2.3.beta2.fc11 Thunderbird/3.0b2 |
On 06/22/2009 08:37 PM, Anthony Liguori wrote:
I'm saying, always enable dirty tracking from start-of-day with KVM. Then the QEMU dirty bitmap is always accurate. The trick is to never start resetting it until you need to do live migration.
That disables large pages and incurs a performance penalty (needlessly setting bits).
The idea being that once the dirty bits have been set, the overhead (hopefully) should be zero.
It's not zero. You also need to clear the bits somehow when you balloon. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.
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