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

["Deepa Srinivasan" <dsriniv@xxxxxxxx>]

Jayaram,

Thanks for the suggestions. I tried both options:

- I didn't have any compiler optimizations enabled before. But I
explicitly disabled them using "gcc -O0" & recompiled. It still crashes
(at the same point in the simulation as before).
- Next, I tried using the modified macro you suggested below as well and
still results in the application crash.

Trying to find any other ways to resolve this problem - any other
suggestions?

Thanks,
Deepa

> 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
>