On Fri, Mar 03, 2017 at 01:40:28PM +0800, Wei Wang wrote:
From: Liang Li <address@hidden>
1) allocating pages (6.5%)
2) sending PFNs to host (68.3%)
3) address translation (6.1%)
4) madvise (19%)
This patch optimizes step 2) by transfering pages to the host in
chunks. A chunk consists of guest physically continuous pages, and
it is offered to the host via a base PFN (i.e. the start PFN of
those physically continuous pages) and the size (i.e. the total
number of the pages). A normal chunk is formated as below:
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| Base (52 bit) | Size (12 bit)|
-----------------------------------------------
For large size chunks, an extended chunk format is used:
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| Base (64 bit) |
-----------------------------------------------
-----------------------------------------------
| Size (64 bit) |
-----------------------------------------------
What's the advantage to extended chunks? IOW, why is the added complexity
of having two chunk formats worth it? You already reduced the overhead by
a factor of 4096 with normal chunks ... how often are extended chunks used
and how much more efficient are they than having several normal chunks?