From: Eric Dumazet
> Sent: 29 January 2016 22:29
...
> On modern intel cpus, this does not matter at all, sure. It took a while
> before "rep movsb" finally did the right thing.
Unfortunately memcpy_to_io() etc now map to 'rep movsb', and that can
only be optimisied for cached addresses.
So copies to/from pcie space get done as byte copies, slower than slow.
The same is true when usespace has used mmap() to directly access
pcie memory.
There isn't a standard wrapper than generates 'rep movsd'.
David
