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

["Deepa Srinivasan" <dsriniv@xxxxxxxx>]

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