Re: [Gems-users] Converting barnes (splash2) to use transactions

[Jayaram Bobba <bobba@xxxxxxxxxxx>]

Deepa,

Your approach to 'transactifying' barnes looks correct. At what 
optimization level are you compiling
Barnes? I would try to compile Barnes with optimizations turned off and 
see if the program works then.
You might also want to modify the transaction macro:

: "l0" /* clobber register */, "memory"                     \

to ensure that the compiler doesn't carry live register values across 
transaction boundaries
Jayaram

Deepa Srinivasan wrote
> I'm trying to use transactions in place of locks in the Barnes application
> from the splash2 suite, with the logTM code. When I run the converted
> application with 2 application threads on a 2-CPU Simics configuration, it
> runs ok. But, when I try the same binary on a 4-CPU configuration, with 4
> application threads, the Barnes application crashes. The simulated system
> or Simics do not crash. At this point, I'm able to save & copy out the
> core file from the crash. Examining the core file (offline, on a different
> system) does not offer any clues - the stack itself seems to be corrupted.
>
> I use gems1.3 and Simics3.0.15.
>
> I turned on logTM debug messages, but didn't turn out to be very useful.
> I'm now trying to capture & analyze cache debug messages as well as logTM.
>
> But, I'd like to make sure that I'm doing the transactional-izing of the
> barnes code accurately.
>
> Below is the transaction code from barnes (load.C) that causes the crash:
> (the commented out ALOCK and AULOCK calls are the old locks code).
> ..............
> (loadtree() function)
>
>       if (*qptr == NULL) {
>          /* lock the parent cell */
>          //ALOCK(CellLock->CL, ((cellptr) mynode)->seqnum % MAXLOCK);
> BEGIN_TRANSACTION(3);
>          if (*qptr == NULL) {
>             le = InitLeaf((cellptr) mynode, ProcessId);
>             Parent(p) = (nodeptr) le;
>             Level(p) = l;
>             ChildNum(p) = le->num_bodies;
>             ChildNum(le) = kidIndex;
>             Bodyp(le)[le->num_bodies++] = p;
>             *qptr = (nodeptr) le;
>             //printf("Xn 3 Level %d\n", l);
>             flag = FALSE;
>          }
>          //AULOCK(CellLock->CL, ((cellptr) mynode)->seqnum % MAXLOCK);
> COMMIT_TRANSACTION(3);
>          /* unlock the parent cell */
>       }
>       if (flag && *qptr && (Type(*qptr) == LEAF)) {
>          /*   reached a "leaf"?      */
>          //ALOCK(CellLock->CL, ((cellptr) mynode)->seqnum % MAXLOCK);
> BEGIN_TRANSACTION(4);
>          /* lock the parent cell */
>          if (Type(*qptr) == LEAF) {             /* still a "leaf"?      */
>             le = (leafptr) *qptr;
>             if (le->num_bodies == MAX_BODIES_PER_LEAF) {
>                *qptr = (nodeptr) SubdivideLeaf(le, (cellptr) mynode, l,
>                                                   ProcessId);
>             }
>             else {
>                Parent(p) = (nodeptr) le;
>                Level(p) = l;
>                ChildNum(p) = le->num_bodies;
>                Bodyp(le)[le->num_bodies++] = p;
>                flag = FALSE;
>             }
>             //printf("Xn 4 Level %d\n", l);
>          }
>          //AULOCK(CellLock->CL, ((cellptr) mynode)->seqnum % MAXLOCK);
> COMMIT_TRANSACTION(4);
>          /* unlock the node           */
>       }
> ............
> Here is the definition I have for the transaction macros:
>
> #define NEW_RUBY_MAGIC_CALL( service )                      \
>     __asm__ __volatile__                                    \
>     ( "sethi %1, %%g0  !magic service\n\t"                  \
>           : /* no outputs */                                \
>       : "r" (0), "i" ((service)<<16)                        \
>           : "l0" /* clobber register */                     \
>         );
>
> #define BEGIN_TRANSACTION(id) NEW_RUBY_MAGIC_CALL((id + 20))
> #define COMMIT_TRANSACTION(id) NEW_RUBY_MAGIC_CALL((id + 40))
> ............
>
> Hoping someone who's done this before can tell me if there's something
> obviously wrong here, in the way I convert to transactions?
>
> Thanks for any help.
> - Deepa
>
>
>
>
>
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