On Tue, 6 Nov 2007, Fabrice Bellard wrote:
Paul Brook wrote:
[...]
Personally I like the locking interface as it allows a zero-copy
implementation. However the kernel uses a copying interface, and my
understanding is that other qemu maintainers also prefer the copying
interface.
At least I don't think it is critical performance wise, especially if
the page flag checks are added ! Before you added the current zero copy
interface, my plan was to use a zero copy interface just for big buffers
such as the one for read/write.
By the time you consider the different combinations of targets & hosts,
most of the opportunities for zero copy are eliminated anyway. Byte
ordering and structure packing amd content differences mean that we can't
do zero-copy except in the rare circumstance that the host & target
match is all of these respects. The read & write buffers would still
benefit from zero copy, but nearly everything else has to be touched
anyway.
Stuart
Stuart R. Anderson [EMAIL PROTECTED]
Network & Software Engineering http://www.netsweng.com/
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