[Hexagon] Initial support for meta schedule tuning

[masahi]

Enables AutoTVM-style, template-based tuning for Hexagon.

To run compiled code on Hexagon, we need to use Hexagon Session object

tvm/python/tvm/contrib/hexagon/session.py

Line 35 in dc522a6

class Session:

in the metaschedule RPCRunner. But for RPC "session", RPCRunner expects an instance of RPCSession,

tvm/python/tvm/rpc/client.py

Line 32 in 53fe596

class RPCSession(object):

, to be created and used by various customizable functions.

Since RPCSession and Hexagon Session have slightly different API, we cannot use RPCRunner with customizable functions directly. So I introduced an alternative implementation of RPCRunner for Hexagon.

The test is disabled for simulator since HexagonLauncherSimulator is not pickle-able due to its multiprocessing.Process attribute:

tvm/python/tvm/contrib/hexagon/build.py

Line 614 in c97895e

self._server_process = mp.Process(target=lambda *a: _start(self, *a))

Output log from tuning vrmpy dense (included in the test)

 ID | Name |      FLOP | Weight | Speed (GFLOPS) | Latency (us) | Weighted Latency (us) | Trials | Terminated
--------------------------------------------------------------------------------------------------------------
  0 | main | 150994944 |      1 |       380.3399 |     397.0000 |              397.0000 |     32 |
--------------------------------------------------------------------------------------------------------------

cc @mehrdadh @csullivan @kparzysz-quic @junrushao @zxybazh

[junrushao]

just a quick typo fix: it's meta schedule not meta scheduler :-) meta schedule is a "meta" schedule that generate basic schedules

[csullivan]

🎉

[csullivan]

It would be really great for this to be tested pre-commit on the simulator so future changes don't regress on the ability to tune. @kparzysz-quic do you think we could remove the use of a local x86 rpc server for targeting the hexagon simulator? Goal would be to make HexagonLauncherSimulator pickleable.

[kparzysz-quic]

I'm not sure I understand the goal. What exactly do you want to make pickleable? Where would it be unpickled?

Right now the simulator fits in the general RPC infrastructure, with the RPC tracker and all. I guess it would be possible to change this, but I'm concerned that it would make Hexagon a "special case", plus I'm really not sure what we gain by doing this.

[masahi]

The issue is that meta schedule RPCRunner uses PopenPoolExuecutor which requires everything that's passed to it be pickle-able:

tvm/python/tvm/contrib/hexagon/meta_schedule.py

Lines 88 to 96 in 9331d9e

	future=self.pool.submit(
	_worker_func,
	self.hexagon_launcher,
	self.evaluator_config,
	self.alloc_repeat,
	str(runner_input.artifact_path),
	tuple(arg_info.as_json() for arg_info in runner_input.args_info),
	),
	timeout_sec=100,

If we try to pass HexagonLauncherSimulator, we get this error https://ci.tlcpack.ai/blue/organizations/jenkins/tvm/detail/PR-12587/3/pipeline/ , Pickling an AuthenticationString object is disallowed for security reasons. Apparently this is coming from trying to pickle

tvm/python/tvm/contrib/hexagon/build.py

Line 614 in c97895e

self._server_process = mp.Process(target=lambda *a: _start(self, *a))

.

The question is, can we remove _server_process from HexagonLauncherSimulator?

[csullivan]

Thanks @masahi @kparzysz-quic - By the way also, not using a local RPC server is not making Hexagon a special case. For example, the CUDA target can be used locally without an x86 RPC server if it is attached to the machine being compiled. For the simulator there may be a similar solution, though it would end up testing a different codepath than runs with HW, so it is worth considering carefully.

[kparzysz-quic]

Thanks, that makes sense. Could we keep the current setup with the x86 server, and add another way to execute the simulator? I think there is value in being able to test the HW code path via simulator (and tests wouldn't need to be changed---right now they are set up to only depend on the device serial to decide whether they should run on HW or sim).