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This adds a new virtual hardware device named "goldfish_pipe"
used to implement a very fast communication channel between the
guest system and the emulator.
IMPORTANT: This depends on a special kernel driver, see:
https://review.source.android.com/#change,22496
Usage from the guest is simply the following:
fd = open("/dev/qemu_pipe", O_RDWR);
const char* pipename = "pipe:<name>";
ret = write(fd, pipename, strlen(pipename)+1);
if (ret < 0) {
/* could not connect to service named <name> */
}
/* now you can read()/write()/close() as a normal
* file descriptor to exchange data with the service.
*/
In addition, this implements the following pipe services in the
emulator:
tcp:<port>
tcp:<hostname>:<port>
unix:<path>
opengles
The 'tcp:' and 'unix:' services simply redirect to a TCP or Unix
socket on the host with minimal
The 'opengles' service simply connects to tcp:locahost:22468 for now.
We may change this to be more configurable in the future, but that's
the port number used by the current experimental OpenGL ES hardware
emulation host libraries / programs.
Benchmarking with a simple ping-pong program shows that the
guest <-> emulator can achieve a roundtrip bandwidth of 192 MB/s
(on a 2.7 Ghz Xeon PC).
Using the tcp: service to talk to a ping-pong server listening
on localhost reaches 102 MB/s on the same machine, using a Unix
socket reaches 140 MB/s.
By contrast, using standard sockets in the guest reaches only
3.8 MB/s on the same machine (and requires special privileges
from the application anyway).
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