ruby: enable multiple clock domains

Information
Submitter:	Nilay Vaish
Repository:	gem5
Branch:	default
Bugs:
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Description

Changeset 9506:ec22f5bb6b33
---------------------------
ruby: enable multiple clock domains
This patch allows ruby to have multiple clock domains. As I understand
with this patch, controllers can have different frequencies. The entire
network needs to run at a single frequency.

The idea is that with in an object, time is treated in terms of cycles.
But the messages that are passed from one entity to another should contain
the time in Ticks. As of now, this is only true for the message buffers,
but not for the links in the network. As I understand the code, all the
entities in different networks (simple, garnet-fixed, garnet-flexible) should
be clocked at the same frequency.

Another problem is that the directory controller has to operate at the same
frequency as the ruby system. This is because the memory controller does
not make use of the Message Buffer, and instead implements a buffer of its
own. So, it has no idea of the frequency at which the directory controller
is operating and uses ruby system's frequency for scheduling events.

Testing Done

Regressions pass. Patch has been tested very lightly using the ruby random tester.

Issue Summary

Description	From	Last Updated	Status
This looks odd to me. Get Cycles and then turn ticks to cycles?	Andreas Hansson	Jan. 31, 2013, 6:09 p.m.	Open
Is getTime not in Cycles?	Andreas Hansson	Jan. 31, 2013, 6:09 p.m.	Open
Naming should change if the type is now Ticks	Andreas Hansson	Jan. 31, 2013, 6:09 p.m.	Open
Change to getTick?	Andreas Hansson	Jan. 31, 2013, 6:09 p.m.	Open
Confusing :-)	Andreas Hansson	Jan. 31, 2013, 6:09 p.m.	Open
Seems unrelated.	Andreas Hansson	Jan. 31, 2013, 6:09 p.m.	Open

This patch is going in a good direction, but at the moment I find the naming and typing rather confusing. (it also highlights that perhaps we should make Tick a class just like Cycles to enable us to specify an explicit constructor and avoid gcc being helpful with implicit casting)

Nilay Vaish Jan. 31, 2013, 9 p.m. (Jan. 31, 2013, 9 p.m.)

I agree with you. I was some times feeling annoyed that gcc does not complain
about one type getting casted to another. The only thing I feel uncomfortable
about is the size of the resulting object. I agree that there will be just one 
data member in that class, and absolutely no virtual functions. My lack of 
compiler knowledge makes me uncomfortable.

There is atleast one place in Ruby where I knowingly did not move from Time
to Cycles because the code assumes that the size of the object that contains
the Time field is not going to change. You might want to blame me for making
such an assumption.

src/mem/ruby/buffers/MessageBuffer.cc (Diff revision 1)

This looks odd to me. Get Cycles and then turn ticks to cycles?

Show all issues

Nilay Vaish Jan. 31, 2013, 9 p.m. (Jan. 31, 2013, 9 p.m.)

The naming is problem here. getDelayedCycles() is what was in use
before and used to return Cycles. But now it returns Ticks instead.
I will change it to getDelayedTicks() throughout.

src/mem/ruby/network/garnet/fixed-pipeline/NetworkInterface_d.cc (Diff revision 1)

Is getTime not in Cycles?

Show all issues

Nilay Vaish Jan. 31, 2013, 9 p.m. (Jan. 31, 2013, 9 p.m.)
```
No, it is in ticks.
```

src/mem/ruby/slicc_interface/Message.hh (Diff revision 1)

Naming should change if the type is now Ticks

Show all issues

src/mem/ruby/slicc_interface/Message.hh (Diff revision 1)

Change to getTick?

Show all issues

src/mem/ruby/slicc_interface/Message.hh (Diff revision 1)

Confusing :-)

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src/mem/ruby/slicc_interface/RubyRequest.hh (Diff revision 1)

Seems unrelated.

Show all issues

Nilay Vaish Jan. 31, 2013, 9 p.m. (Jan. 31, 2013, 9 p.m.)
```
Agreed. Please let it go through.
```

Description:

~		Changeset 9500:5dbd52da6716
	~	Changeset 9507:1b6c00205a89

		ruby: enable multiple clock domanins
		This patch allows ruby to have multiple clock domains. As I understand
		with this patch, controllers can have different frequencies. The entire
		network needs to run at a single frequency.

		The idea is that with in an object, time is treated in terms of cycles.
		But the messages that are passed from one entity to another should contain
~		the time in cycles. As of now, this is only true for the message buffers,
	~	the time in Ticks. As of now, this is only true for the message buffers,
		but not for the links in the network. As I understand the code, all the
		entities in different networks (simple, garnet-fixed, garnet-flexible) should
		be clocked at the same frequency.

		Another problem is that the directory controller has to operate at the same
		frequency as the ruby system. This is because the memory controller does
		not make use of the Message Buffer, and instead implements a buffer of its
		own. So, it has no idea of the frequency at which the directory controller
		is operating and uses ruby system's frequency for scheduling events.

Diff:

Revision 2 (+60 -100)

Show changes

	src/mem/ruby/buffers/MessageBuffer.cc
	src/mem/ruby/network/garnet/fixed-pipeline/NetworkInterface_d.cc
	src/mem/ruby/network/garnet/flexible-pipeline/NetworkInterface.cc
	src/mem/ruby/network/simple/Throttle.cc
	src/mem/ruby/profiler/Profiler.cc
	src/mem/ruby/slicc_interface/Message.hh
	src/mem/ruby/slicc_interface/NetworkMessage.hh
	src/mem/ruby/slicc_interface/RubyRequest.hh
	7 more

From my side is fine. I can imagine it shakes some stats around though...

Nilay Vaish Feb. 1, 2013, 1:27 a.m. (Feb. 1, 2013, 1:27 a.m.)

I think regressions don't change, though I did say in a different
thread that they do. I'll run regressions once again and whatever
is the outcome, I'll take that.

Does any one else has any comments to make, especially those who
use ruby more often? Brad, Derek, Jason, Joel, Marc, ..., any comments?

Summary:

-	ruby: enable multiple clock domanins
+	ruby: enable multiple clock domains

Description:

~		Changeset 9507:1b6c00205a89
	~	Changeset 9506:ec22f5bb6b33

~		ruby: enable multiple clock domanins
	~	ruby: enable multiple clock domains
		This patch allows ruby to have multiple clock domains. As I understand
		with this patch, controllers can have different frequencies. The entire
		network needs to run at a single frequency.

		The idea is that with in an object, time is treated in terms of cycles.
		But the messages that are passed from one entity to another should contain
		the time in Ticks. As of now, this is only true for the message buffers,
		but not for the links in the network. As I understand the code, all the
		entities in different networks (simple, garnet-fixed, garnet-flexible) should
		be clocked at the same frequency.

		Another problem is that the directory controller has to operate at the same
		frequency as the ruby system. This is because the memory controller does
		not make use of the Message Buffer, and instead implements a buffer of its
		own. So, it has no idea of the frequency at which the directory controller
		is operating and uses ruby system's frequency for scheduling events.

Diff:

Revision 3 (+145 -150)

Show changes

	src/mem/ruby/buffers/MessageBuffer.hh
	src/mem/ruby/buffers/MessageBuffer.cc
	src/mem/ruby/network/garnet/fixed-pipeline/NetworkInterface_d.cc
	src/mem/ruby/network/garnet/flexible-pipeline/NetworkInterface.cc
	src/mem/ruby/network/simple/PerfectSwitch.hh
	src/mem/ruby/network/simple/PerfectSwitch.cc
	src/mem/ruby/network/simple/Switch.cc
	src/mem/ruby/network/simple/Throttle.hh
	15 more

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Issue Summary

Description:

Changeset 9500:5dbd52da6716

Changeset 9507:1b6c00205a89

Diff:

Summary:

Description:

Changeset 9507:1b6c00205a89

Changeset 9506:ec22f5bb6b33

Diff:

Status: Closed (submitted)