What threshold do you use?
On Tue, 4 Jan 2011, Arkaprava Basu wrote:
Hi Nilay,
On deadlock issue with MESI_CMP_directory :
Yes, this can happen as ruby_tester or Sequencer only reports *possible*
deadlocks. With higher number of processors there is more contention (and
thus latency) and it can mistakenly report deadlock. I generally look at the
protocol trace to figure out whether there is actually any deadlock or not.
You can also try doubling the Sequencer deadlock threshold and see if the
problem goes away. If its a true deadlock, it will break again.
On some related note, as Brad has pointed out MESI_CMP_directory has its
share of issues. Recently one of Prof. Sarita Adve's student e-mailed us
(Multifacet) about 6 bugs he found while model checking the
MESI_CMP_directory (including a major one). I took some time to look at them
and it seems like MESI_CMP_directory is now fixed (hopefully). The modified
protocol is now passing 1M checks with 16 processors with multiple random
seeds. I can locally coordinate with you on this, if you want.
Thanks
Arka
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