In the process of updating stats, I've had scons recompile a few Ruby
controller .cc files and then rebuild the gem5 binary in cases where
nothing else has changed, forcing you to re-run tests unnecessarily, which
is a huge pain particularly when you're running the long tests.
I know that the generated Ruby files get re-generated every time scons is
run so that it can deduce what the output files are, but since scons is
signature-based, re-generating an identical file should not cause a
rebuild. I figured out that the files really were changing, and captured a
bunch of diffs like this:
--- X86/mem/protocol/DMA_Controller.cc.orig 2013-09-29
17:29:26.529556643 -0700
+++ X86/mem/protocol/DMA_Controller.cc 2013-09-29 17:29:39.457556581 -0700
@@ -50,7 +50,7 @@
: AbstractController(p)
{
m_name = "DMA";
- m_max_in_port_rank = 6;
+ m_max_in_port_rank = 1;
m_dma_sequencer_ptr = p->dma_sequencer;
m_request_latency = p->request_latency;
m_dma_sequencer_ptr->setController(this);
Note that this happened across all ISAs, and affected not just
DMA_Controller.cc but several other *_Controller.cc files also --
Directory_Controller.cc, L1Cache_Controller.cc, and (where applicable)
L2Cache_Controller.cc. In this one particular run of scons, all the files
changed m_max_in_port_rank from 6 to 1, though on another run I saw the
value change from 6 to 4. (I think it just happened to be 6 the time I
remembered to copy the files for diffing.)
So basically slicc seems to be spitting out nondeterministic output. I'll
guess that whatever this value is, it is being generated from an
uninitialized value somewhere. I don't know slicc well enough to track
this down easily, and I've already spent far too much of the weekend
wrestling with stats updates and other issues, so I'm not going to pursue
it farther right now. It would be really great if someone could follow up
on this though.
I don't recall this happening before, so I wouldn't be surprised if it's
the result of some change that occurred in the last several months.
Thanks,
Steve
_______________________________________________
gem5-dev mailing list
[email protected]
http://m5sim.org/mailman/listinfo/gem5-dev
