[Gems-users] Three questions about transactional memory

[eakpinar <eakpinar@xxxxxx>]

Hello all

I was looking into implementation of LogTM-SE and was wondering if you
could help me out with a few questions. 

- I run STAMP benchmarks. With 1 processor single threaded runs (1 SMT
thread), I get matches and empty checks for signatures in stats. (Even
with perfect signatures). I cannot account for the matching signatures
checks. With 1 processor runs, there should not be any other non-empty
signature (except for the main running thread's). So there should not be
any matching checks. About empty checks, I suspect execution gets
interrupted by non-tx.nal stuff (like page faults or similar OS
activity) and thus the process gets descheduled. When it gets scheduled
again, it checks again the summary signature (which is empty) and hence
the number of empty checks.
- I am trying to understand how non-tx.nal accesses are handled during
transactions. For instance, what happens when there is a page fault
during a transaction? Is conflict detection (and thus signature
checking) carried out? Or are non-tx.nal accesses allowed to happen
without any signature checking? (Thus stability and correctness are
maintained by the coherence protocol)
- Commits are listed in stats with XIDs (transaction IDs I assume).
Regardless of the number of processors, there always seem to be 5 XIDs.
Any
idea how XIDs are assigned?

I'd appreciate any response. Thanks in advance.

Note : I am using gems-2.1.1 with simics-3.0.31

Ege

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