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

[Jayaram Bobba <bobba@xxxxxxxxxxx>]

I cannot think of a simple way to catch a bug in this case. We have also 
not tested LogTM with
Simics 3.0.x. I am not sure if there are any issues there.

On a side note, we will be releasing GEMS 2.0 shortly. It will have a 
much more stable implementation
of LogTM-SE and more built-in debugging features. It should make your 
job easier. I would recommend waiting
for it if you have a couple of weeks in hand.

Jayaram

Deepa Srinivasan wrote:
> 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
> >
> >     
> _______________________________________________
> Gems-users mailing list
> Gems-users@xxxxxxxxxxx
> https://lists.cs.wisc.edu/mailman/listinfo/gems-users
> Use Google to search the GEMS Users mailing list by adding "site:https://lists.cs.wisc.edu/archive/gems-users/"; to your search.
>