Re: [Gems-users] logTM conflict resolution

[Jayaram Bobba <bobba@xxxxxxxxxxx>]

Pretty close...
For HYBRID, the older transaction is stalled if the younger transaction 
has either read-modified or modified
the conflicting address. Else younger is aborted.

Jayaram

Jim Leek wrote:
> I've been trying to figure out exactly what EE_HYBRID does.  I've 
> looked at the wiki and I've looked in TransactionConflictManager.C, 
> but I don't get it.  (Actually, I can't find anything described in 
> TransactionConflictManager.C, there's only one reference to HYBRID in 
> the whole file, and it does the same thing as TIMESTAMP.)  Anyway 
> here's my guess, let me know if it's right.
> TIMESTAMP will kill the younger transaction in any conflict.
> HYBRID will allow the younger transaction to live iff the value in 
> conflict is ONLY in the younger transaction's write set.  In other 
> words, if the younger transaction read or read and modified the 
> conflicting value, it is kill, but if the younger transaction only 
> wrote the value, the younger transaction is stalled until the older 
> transaction commits.
> Maybe?
>
> Thanks,
> Jim
>
> On Sun, Mar 9, 2008 at 2:27 PM, Jayaram Bobba <bobba@xxxxxxxxxxx 
> <mailto:bobba@xxxxxxxxxxx>> wrote:
>     $GEMS/ruby/log_tm/TransactionConflictManager.C gives a more precise
>     description of the conflict resolution policies
>     than the wiki.
>
>     The conflict resolution policies used in the pathologies paper:
>     EE - BASE and HYBRID
>     EL - BASE and TIMESTAMP
>     LL - BASE
>
>     The XACT_NO_BACKOFF parameter determines if software backoff is used
>     along with any particular policy. Look at
>     gen-scripts.py to see which policies use this parameter.
>
>     Jayaram
>
>
>     Jim Leek wrote:
>     > In the Pathologies paper it gives a set of the different kinds of
>     > Transactional memory styles, and they have different conflict
>     > resolution methods.  LL is committer wins, EL is Requester wins, and
>     > EE is requester stalls.  However, I don't really see these
>     options in
>     > rubyconfig.defaults.  This is what the wiki says:
>     >
>     > *XACT_EAGER_CD*: (true or false) Setting to true enables eager
>     > conflict detection. Otherwise uses lazy conflict detection.
>     >
>     > *XACT_LAZY_VM*: (true or false) Setting to true enables lazy version
>     > management via an infinite write buffer. Otherwise uses eager
>     version
>     > management. *Must also set XACT_MEMORY to true during protocol
>     > compilation, or else appropriate Simics callbacks will not get
>     registered.
>     >
>     > **XACT_CONFLICT_RES*: (BASE, TIMESTAMP, HYBRID, or CYCLE) Different
>     > policies of conflict resolution. BASE aborts the requestor whenever
>     > there's a conflict. TIMESTAMP aborts a requestor only if the
>     requestor
>     > is younger than the conflicting processor. HYBRID aborts a younger
>     > transaction in favor of an older requesting transaction if the
>     younger
>     > has the conflicting block in its read set only. CYCLE always
>     indicates
>     > a conflict with other transactions, and is used to immediately
>     trap to
>     > a software contention manager.
>     >
>     > so, if I use EE-base, does requester stall? EL's policy of requester
>     > always wins doesn't even seem to be an option?  (I'm guessing that
>     > EL-base actually does this.)
>     >
>     > Thanks,
>     > Jim
>     >
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