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http://reviews.gem5.org/r/3331/
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Review request for Default.


Repository: gem5


Description
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Changeset 11332:1b834b01d375
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ruby: [DRAFT] Finite dir <-> mem buffering and flow-control

Ruby directory controllers used unbounded Queued*Ports to communicate with
memory controllers. This causes buffer bloat in memory intensive applications,
resulting in unreasonably high memory access latencies. To fix this issue,
adjust the directory <-> memory interface to implement flow control, including
retries, and add the capability to set finite buffer sizes.


Diffs
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  src/mem/protocol/RubySlicc_MemControl.sm 10647f5d0f7f 
  src/mem/ruby/slicc_interface/AbstractController.hh 10647f5d0f7f 
  src/mem/ruby/slicc_interface/AbstractController.cc 10647f5d0f7f 
  src/mem/slicc/symbols/StateMachine.py 10647f5d0f7f 
  src/mem/protocol/RubySlicc_Defines.sm 10647f5d0f7f 

Diff: http://reviews.gem5.org/r/3331/diff/


Testing
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Changed MOESI_hammer directory to use the new memory interface as an example: 
http://reviews.gem5.org/r/3332/
Tested MOESI_hammer with finite buffering using patch here: 
http://pages.cs.wisc.edu/~hestness/links/MOESI_hammer_test_finite_queues
Ran this microbenchmark: 
http://pages.cs.wisc.edu/~hestness/links/cpu_memory_demand

As an example, this was a command line:

outdir=MOESI_hammer_dramctrl_ruby_finite_buffering; mkdir -p $outdir; 
../build/X86_MOESI_hammer/gem5.opt --debug-flag=DRAM --outdir=$outdir 
../configs/example/se.py --ruby --cpu-type=detailed --l1d_size=4kB 
--l2_size=4kB -c gem5_fusion_cpu_memory_demand -o "-a 4096 -i 10 -s 16" 
--output=$outdir/system.out --errout=$outdir/system.out >& $outdir/gem5.out


Thanks,

Joel Hestness

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