rts/Sparks.c

   1 /* ---------------------------------------------------------------------------
   2  *
   3  * (c) The GHC Team, 2000-2006
   4  *
   5  * Sparking support for PARALLEL_HASKELL and THREADED_RTS versions of the RTS.
   6  *
   7  * -------------------------------------------------------------------------*/
   8
   9 #include "PosixSource.h"
  10 #include "Rts.h"
  11 #include "Storage.h"
  12 #include "Schedule.h"
  13 #include "SchedAPI.h"
  14 #include "RtsFlags.h"
  15 #include "RtsUtils.h"
  16 #include "ParTicky.h"
  17 # if defined(PARALLEL_HASKELL)
  18 # include "ParallelRts.h"
  19 # include "GranSimRts.h"   // for GR_...
  20 # elif defined(GRAN)
  21 # include "GranSimRts.h"
  22 # endif
  23 #include "Sparks.h"
  24 #include "Trace.h"
  25
  26 #if defined(THREADED_RTS) || defined(PARALLEL_HASKELL)
  27
  28 static INLINE_ME void bump_hd (StgSparkPool *p)
  29 { p->hd++; if (p->hd == p->lim) p->hd = p->base; }
  30
  31 static INLINE_ME void bump_tl (StgSparkPool *p)
  32 { p->tl++; if (p->tl == p->lim) p->tl = p->base; }
  33
  34 /* -----------------------------------------------------------------------------
  35  *
  36  * Initialising spark pools.
  37  *
  38  * -------------------------------------------------------------------------- */
  39
  40 static void
  41 initSparkPool(StgSparkPool *pool)
  42 {
  43     pool->base = stgMallocBytes(RtsFlags.ParFlags.maxLocalSparks
  44                                 * sizeof(StgClosure *),
  45                                 "initSparkPools");
  46     pool->lim = pool->base + RtsFlags.ParFlags.maxLocalSparks;
  47     pool->hd  = pool->base;
  48     pool->tl  = pool->base;
  49 }
  50
  51 void
  52 initSparkPools( void )
  53 {
  54 #ifdef THREADED_RTS
  55     /* walk over the capabilities, allocating a spark pool for each one */
  56     nat i;
  57     for (i = 0; i < n_capabilities; i++) {
  58         initSparkPool(&capabilities[i].r.rSparks);
  59     }
  60 #else
  61     /* allocate a single spark pool */
  62     initSparkPool(&MainCapability.r.rSparks);
  63 #endif
  64 }
  65
  66 void
  67 freeSparkPool(StgSparkPool *pool) {
  68     stgFree(pool->base);
  69 }
  70
  71 /* -----------------------------------------------------------------------------
  72  *
  73  * findSpark: find a spark on the current Capability that we can fork
  74  * into a thread.
  75  *
  76  * -------------------------------------------------------------------------- */
  77
  78 StgClosure *
  79 findSpark (Capability *cap)
  80 {
  81     StgSparkPool *pool;
  82     StgClosure *spark;
  83
  84     pool = &(cap->r.rSparks);
  85     ASSERT_SPARK_POOL_INVARIANTS(pool);
  86
  87     while (pool->hd != pool->tl) {
  88         spark = *pool->hd;
  89         bump_hd(pool);
  90         if (closure_SHOULD_SPARK(spark)) {
  91 #ifdef GRAN
  92             if (RtsFlags.ParFlags.ParStats.Sparks)
  93                 DumpRawGranEvent(CURRENT_PROC, CURRENT_PROC,
  94                                  GR_STEALING, ((StgTSO *)NULL), spark,
  95                                  0, 0 /* spark_queue_len(ADVISORY_POOL) */);
  96 #endif
  97             return spark;
  98         }
  99     }
 100     // spark pool is now empty
 101     return NULL;
 102 }
 103
 104 /* -----------------------------------------------------------------------------
 105  *
 106  * Turn a spark into a real thread
 107  *
 108  * -------------------------------------------------------------------------- */
 109
 110 void
 111 createSparkThread (Capability *cap, StgClosure *p)
 112 {
 113     StgTSO *tso;
 114
 115     tso = createGenThread (cap, RtsFlags.GcFlags.initialStkSize, p);
 116     appendToRunQueue(cap,tso);
 117 }
 118
 119 /* -----------------------------------------------------------------------------
 120  *
 121  * Create a new spark
 122  *
 123  * -------------------------------------------------------------------------- */
 124
 125 #define DISCARD_NEW
 126
 127 StgInt
 128 newSpark (StgRegTable *reg, StgClosure *p)
 129 {
 130     StgSparkPool *pool = &(reg->rSparks);
 131
 132     /* I am not sure whether this is the right thing to do.
 133      * Maybe it is better to exploit the tag information
 134      * instead of throwing it away?
 135      */
 136     p = UNTAG_CLOSURE(p);
 137
 138     ASSERT_SPARK_POOL_INVARIANTS(pool);
 139
 140     if (closure_SHOULD_SPARK(p)) {
 141 #ifdef DISCARD_NEW
 142         StgClosure **new_tl;
 143         new_tl = pool->tl + 1;
 144         if (new_tl == pool->lim) { new_tl = pool->base; }
 145         if (new_tl != pool->hd) {
 146             *pool->tl = p;
 147             pool->tl = new_tl;
 148         } else if (!closure_SHOULD_SPARK(*pool->hd)) {
 149             // if the old closure is not sparkable, discard it and
 150             // keep the new one.  Otherwise, keep the old one.
 151             *pool->tl = p;
 152             bump_hd(pool);
 153         }
 154 #else  /* DISCARD OLD */
 155         *pool->tl = p;
 156         bump_tl(pool);
 157         if (pool->tl == pool->hd) { bump_hd(pool); }
 158 #endif
 159     }
 160
 161     ASSERT_SPARK_POOL_INVARIANTS(pool);
 162     return 1;
 163 }
 164
 165 /* -----------------------------------------------------------------------------
 166  * Mark all nodes pointed to by sparks in the spark queues (for GC) Does an
 167  * implicit slide i.e. after marking all sparks are at the beginning of the
 168  * spark pool and the spark pool only contains sparkable closures
 169  * -------------------------------------------------------------------------- */
 170
 171 void
 172 markSparkQueue (evac_fn evac, void *user, Capability *cap)
 173 {
 174     StgClosure *spark, **sparkp, **to_sparkp;
 175     nat n, pruned_sparks; // stats only
 176     StgSparkPool *pool;
 177
 178     PAR_TICKY_MARK_SPARK_QUEUE_START();
 179
 180     n = 0;
 181     pruned_sparks = 0;
 182
 183     pool = &(cap->r.rSparks);
 184
 185     ASSERT_SPARK_POOL_INVARIANTS(pool);
 186
 187     sparkp = pool->hd;
 188     to_sparkp = pool->hd;
 189     while (sparkp != pool->tl) {
 190         ASSERT(*sparkp!=NULL);
 191         ASSERT(LOOKS_LIKE_CLOSURE_PTR(((StgClosure *)*sparkp)));
 192         // ToDo?: statistics gathering here (also for GUM!)
 193         evac(user,sparkp);
 194         spark = *sparkp;
 195         if (!closure_SHOULD_SPARK(spark)) {
 196             pruned_sparks++;
 197         } else{
 198             *to_sparkp++ = spark;
 199             if (to_sparkp == pool->lim) {
 200                 to_sparkp = pool->base;
 201             }
 202             n++;
 203         }
 204         sparkp++;
 205         if (sparkp == pool->lim) {
 206             sparkp = pool->base;
 207         }
 208     }
 209     pool->tl = to_sparkp;
 210
 211     PAR_TICKY_MARK_SPARK_QUEUE_END(n);
 212
 213     debugTrace(DEBUG_sched,
 214                "marked %d sparks, pruned %d sparks",
 215                n, pruned_sparks);
 216
 217     debugTrace(DEBUG_sched,
 218                "new spark queue len=%d; (hd=%p; tl=%p)",
 219                sparkPoolSize(pool), pool->hd, pool->tl);
 220 }
 221
 222 void
 223 traverseSparkQueue (evac_fn evac, void *user, Capability *cap)
 224 {
 225     StgClosure **sparkp;
 226     StgSparkPool *pool;
 227
 228     pool = &(cap->r.rSparks);
 229     sparkp = pool->hd;
 230     while (sparkp != pool->tl) {
 231         evac(sparkp, user);
 232         sparkp++;
 233         if (sparkp == pool->lim) {
 234             sparkp = pool->base;
 235         }
 236     }
 237 }
 238
 239 #else
 240
 241 StgInt
 242 newSpark (StgRegTable *reg STG_UNUSED, StgClosure *p STG_UNUSED)
 243 {
 244     /* nothing */
 245     return 1;
 246 }
 247
 248
 249 #endif /* PARALLEL_HASKELL || THREADED_RTS */
 250
 251
 252 /* -----------------------------------------------------------------------------
 253  *
 254  * GRAN & PARALLEL_HASKELL stuff beyond here.
 255  *
 256  * -------------------------------------------------------------------------- */
 257
 258 #if defined(PARALLEL_HASKELL) || defined(GRAN)
 259
 260 static void slide_spark_pool( StgSparkPool *pool );
 261
 262 rtsBool
 263 add_to_spark_queue( StgClosure *closure, StgSparkPool *pool )
 264 {
 265   if (pool->tl == pool->lim)
 266     slide_spark_pool(pool);
 267
 268   if (closure_SHOULD_SPARK(closure) &&
 269       pool->tl < pool->lim) {
 270     *(pool->tl++) = closure;
 271
 272 #if defined(PARALLEL_HASKELL)
 273     // collect parallel global statistics (currently done together with GC stats)
 274     if (RtsFlags.ParFlags.ParStats.Global &&
 275         RtsFlags.GcFlags.giveStats > NO_GC_STATS) {
 276       // debugBelch("Creating spark for %x @ %11.2f\n", closure, usertime());
 277       globalParStats.tot_sparks_created++;
 278     }
 279 #endif
 280     return rtsTrue;
 281   } else {
 282 #if defined(PARALLEL_HASKELL)
 283     // collect parallel global statistics (currently done together with GC stats)
 284     if (RtsFlags.ParFlags.ParStats.Global &&
 285         RtsFlags.GcFlags.giveStats > NO_GC_STATS) {
 286       //debugBelch("Ignoring spark for %x @ %11.2f\n", closure, usertime());
 287       globalParStats.tot_sparks_ignored++;
 288     }
 289 #endif
 290     return rtsFalse;
 291   }
 292 }
 293
 294 static void
 295 slide_spark_pool( StgSparkPool *pool )
 296 {
 297   StgClosure **sparkp, **to_sparkp;
 298
 299   sparkp = pool->hd;
 300   to_sparkp = pool->base;
 301   while (sparkp < pool->tl) {
 302     ASSERT(to_sparkp<=sparkp);
 303     ASSERT(*sparkp!=NULL);
 304     ASSERT(LOOKS_LIKE_GHC_INFO((*sparkp)->header.info));
 305
 306     if (closure_SHOULD_SPARK(*sparkp)) {
 307       *to_sparkp++ = *sparkp++;
 308     } else {
 309       sparkp++;
 310     }
 311   }
 312   pool->hd = pool->base;
 313   pool->tl = to_sparkp;
 314 }
 315
 316 void
 317 disposeSpark(spark)
 318 StgClosure *spark;
 319 {
 320 #if !defined(THREADED_RTS)
 321   Capability *cap;
 322   StgSparkPool *pool;
 323
 324   cap = &MainRegTable;
 325   pool = &(cap->rSparks);
 326   ASSERT(pool->hd <= pool->tl && pool->tl <= pool->lim);
 327 #endif
 328   ASSERT(spark != (StgClosure *)NULL);
 329   /* Do nothing */
 330 }
 331
 332
 333 #elif defined(GRAN)
 334
 335 /*
 336    Search the spark queue of the proc in event for a spark that's worth
 337    turning into a thread
 338    (was gimme_spark in the old RTS)
 339 */
 340 void
 341 findLocalSpark (rtsEvent *event, rtsBool *found_res, rtsSparkQ *spark_res)
 342 {
 343    PEs proc = event->proc,       /* proc to search for work */
 344        creator = event->creator; /* proc that requested work */
 345    StgClosure* node;
 346    rtsBool found;
 347    rtsSparkQ spark_of_non_local_node = NULL,
 348              spark_of_non_local_node_prev = NULL,
 349              low_priority_spark = NULL,
 350              low_priority_spark_prev = NULL,
 351              spark = NULL, prev = NULL;
 352
 353    /* Choose a spark from the local spark queue */
 354    prev = (rtsSpark*)NULL;
 355    spark = pending_sparks_hds[proc];
 356    found = rtsFalse;
 357
 358    // ToDo: check this code & implement local sparking !! -- HWL
 359    while (!found && spark != (rtsSpark*)NULL)
 360      {
 361        ASSERT((prev!=(rtsSpark*)NULL || spark==pending_sparks_hds[proc]) &&
 362               (prev==(rtsSpark*)NULL || prev->next==spark) &&
 363               (spark->prev==prev));
 364        node = spark->node;
 365        if (!closure_SHOULD_SPARK(node))
 366          {
 367            IF_GRAN_DEBUG(checkSparkQ,
 368                          debugBelch("^^ pruning spark %p (node %p) in gimme_spark",
 369                                spark, node));
 370
 371            if (RtsFlags.GranFlags.GranSimStats.Sparks)
 372              DumpRawGranEvent(proc, (PEs)0, SP_PRUNED,(StgTSO*)NULL,
 373                               spark->node, spark->name, spark_queue_len(proc));
 374
 375            ASSERT(spark != (rtsSpark*)NULL);
 376            ASSERT(SparksAvail>0);
 377            --SparksAvail;
 378
 379            ASSERT(prev==(rtsSpark*)NULL || prev->next==spark);
 380            spark = delete_from_sparkq (spark, proc, rtsTrue);
 381            if (spark != (rtsSpark*)NULL)
 382              prev = spark->prev;
 383            continue;
 384          }
 385        /* -- node should eventually be sparked */
 386        else if (RtsFlags.GranFlags.PreferSparksOfLocalNodes &&
 387                !IS_LOCAL_TO(PROCS(node),CurrentProc))
 388          {
 389            barf("Local sparking not yet implemented");
 390
 391            /* Remember first low priority spark */
 392            if (spark_of_non_local_node==(rtsSpark*)NULL) {
 393              spark_of_non_local_node_prev = prev;
 394              spark_of_non_local_node = spark;
 395               }
 396
 397            if (spark->next == (rtsSpark*)NULL) {
 398              /* ASSERT(spark==SparkQueueTl);  just for testing */
 399              prev = spark_of_non_local_node_prev;
 400              spark = spark_of_non_local_node;
 401              found = rtsTrue;
 402              break;
 403            }
 404
 405 # if defined(GRAN) && defined(GRAN_CHECK)
 406            /* Should never happen; just for testing
 407            if (spark==pending_sparks_tl) {
 408              debugBelch("ReSchedule: Last spark != SparkQueueTl\n");
 409                 stg_exit(EXIT_FAILURE);
 410                 } */
 411 # endif
 412            prev = spark;
 413            spark = spark->next;
 414            ASSERT(SparksAvail>0);
 415            --SparksAvail;
 416            continue;
 417          }
 418        else if ( RtsFlags.GranFlags.DoPrioritySparking ||
 419                  (spark->gran_info >= RtsFlags.GranFlags.SparkPriority2) )
 420          {
 421            if (RtsFlags.GranFlags.DoPrioritySparking)
 422              barf("Priority sparking not yet implemented");
 423
 424            found = rtsTrue;
 425          }
 426 #if 0
 427        else /* only used if SparkPriority2 is defined */
 428          {
 429            /* ToDo: fix the code below and re-integrate it */
 430            /* Remember first low priority spark */
 431            if (low_priority_spark==(rtsSpark*)NULL) {
 432              low_priority_spark_prev = prev;
 433              low_priority_spark = spark;
 434            }
 435
 436            if (spark->next == (rtsSpark*)NULL) {
 437                 /* ASSERT(spark==spark_queue_tl);  just for testing */
 438              prev = low_priority_spark_prev;
 439              spark = low_priority_spark;
 440              found = rtsTrue;       /* take low pri spark => rc is 2  */
 441              break;
 442            }
 443
 444            /* Should never happen; just for testing
 445            if (spark==pending_sparks_tl) {
 446              debugBelch("ReSchedule: Last spark != SparkQueueTl\n");
 447                 stg_exit(EXIT_FAILURE);
 448              break;
 449            } */
 450            prev = spark;
 451            spark = spark->next;
 452
 453            IF_GRAN_DEBUG(pri,
 454                          debugBelch("++ Ignoring spark of priority %u (SparkPriority=%u); node=%p; name=%u\n",
 455                                spark->gran_info, RtsFlags.GranFlags.SparkPriority,
 456                                spark->node, spark->name);)
 457            }
 458 #endif
 459    }  /* while (spark!=NULL && !found) */
 460
 461    *spark_res = spark;
 462    *found_res = found;
 463 }
 464
 465 /*
 466   Turn the spark into a thread.
 467   In GranSim this basically means scheduling a StartThread event for the
 468   node pointed to by the spark at some point in the future.
 469   (was munch_spark in the old RTS)
 470 */
 471 rtsBool
 472 activateSpark (rtsEvent *event, rtsSparkQ spark)
 473 {
 474   PEs proc = event->proc,       /* proc to search for work */
 475       creator = event->creator; /* proc that requested work */
 476   StgTSO* tso;
 477   StgClosure* node;
 478   rtsTime spark_arrival_time;
 479
 480   /*
 481      We've found a node on PE proc requested by PE creator.
 482      If proc==creator we can turn the spark into a thread immediately;
 483      otherwise we schedule a MoveSpark event on the requesting PE
 484   */
 485
 486   /* DaH Qu' yIchen */
 487   if (proc!=creator) {
 488
 489     /* only possible if we simulate GUM style fishing */
 490     ASSERT(RtsFlags.GranFlags.Fishing);
 491
 492     /* Message packing costs for sending a Fish; qeq jabbI'ID */
 493     CurrentTime[proc] += RtsFlags.GranFlags.Costs.mpacktime;
 494
 495     if (RtsFlags.GranFlags.GranSimStats.Sparks)
 496       DumpRawGranEvent(proc, (PEs)0, SP_EXPORTED,
 497                        (StgTSO*)NULL, spark->node,
 498                        spark->name, spark_queue_len(proc));
 499
 500     /* time of the spark arrival on the remote PE */
 501     spark_arrival_time = CurrentTime[proc] + RtsFlags.GranFlags.Costs.latency;
 502
 503     new_event(creator, proc, spark_arrival_time,
 504               MoveSpark,
 505               (StgTSO*)NULL, spark->node, spark);
 506
 507     CurrentTime[proc] += RtsFlags.GranFlags.Costs.mtidytime;
 508
 509   } else { /* proc==creator i.e. turn the spark into a thread */
 510
 511     if ( RtsFlags.GranFlags.GranSimStats.Global &&
 512          spark->gran_info < RtsFlags.GranFlags.SparkPriority2 ) {
 513
 514       globalGranStats.tot_low_pri_sparks++;
 515       IF_GRAN_DEBUG(pri,
 516                     debugBelch("++ No high priority spark available; low priority (%u) spark chosen: node=%p; name=%u\n",
 517                           spark->gran_info,
 518                           spark->node, spark->name));
 519     }
 520
 521     CurrentTime[proc] += RtsFlags.GranFlags.Costs.threadcreatetime;
 522
 523     node = spark->node;
 524
 525 # if 0
 526     /* ToDo: fix the GC interface and move to StartThread handling-- HWL */
 527     if (GARBAGE COLLECTION IS NECESSARY) {
 528       /* Some kind of backoff needed here in case there's too little heap */
 529 #  if defined(GRAN_CHECK) && defined(GRAN)
 530       if (RtsFlags.GcFlags.giveStats)
 531         fprintf(RtsFlags.GcFlags.statsFile,"***** vIS Qu' chen veQ boSwI'; spark=%p, node=%p;  name=%u\n",
 532                 /* (found==2 ? "no hi pri spark" : "hi pri spark"), */
 533                 spark, node, spark->name);
 534 #  endif
 535       new_event(CurrentProc, CurrentProc, CurrentTime[CurrentProc]+1,
 536                   FindWork,
 537                   (StgTSO*)NULL, (StgClosure*)NULL, (rtsSpark*)NULL);
 538       barf("//// activateSpark: out of heap ; ToDo: call GarbageCollect()");
 539       GarbageCollect(GetRoots, rtsFalse);
 540       // HWL old: ReallyPerformThreadGC(TSO_HS+TSO_CTS_SIZE,rtsFalse);
 541       // HWL old: SAVE_Hp -= TSO_HS+TSO_CTS_SIZE;
 542       spark = NULL;
 543       return; /* was: continue; */ /* to the next event, eventually */
 544     }
 545 # endif
 546
 547     if (RtsFlags.GranFlags.GranSimStats.Sparks)
 548       DumpRawGranEvent(CurrentProc,(PEs)0,SP_USED,(StgTSO*)NULL,
 549                        spark->node, spark->name,
 550                        spark_queue_len(CurrentProc));
 551
 552     new_event(proc, proc, CurrentTime[proc],
 553               StartThread,
 554               END_TSO_QUEUE, node, spark); // (rtsSpark*)NULL);
 555
 556     procStatus[proc] = Starting;
 557   }
 558 }
 559
 560 /* -------------------------------------------------------------------------
 561    This is the main point where handling granularity information comes into
 562    play.
 563    ------------------------------------------------------------------------- */
 564
 565 #define MAX_RAND_PRI    100
 566
 567 /*
 568    Granularity info transformers.
 569    Applied to the GRAN_INFO field of a spark.
 570 */
 571 STATIC_INLINE nat  ID(nat x) { return(x); };
 572 STATIC_INLINE nat  INV(nat x) { return(-x); };
 573 STATIC_INLINE nat  IGNORE(nat x) { return (0); };
 574 STATIC_INLINE nat  RAND(nat x) { return ((random() % MAX_RAND_PRI) + 1); }
 575
 576 /* NB: size_info and par_info are currently unused (what a shame!) -- HWL */
 577 rtsSpark *
 578 newSpark(node,name,gran_info,size_info,par_info,local)
 579 StgClosure *node;
 580 nat name, gran_info, size_info, par_info, local;
 581 {
 582   nat pri;
 583   rtsSpark *newspark;
 584
 585   pri = RtsFlags.GranFlags.RandomPriorities ? RAND(gran_info) :
 586         RtsFlags.GranFlags.InversePriorities ? INV(gran_info) :
 587         RtsFlags.GranFlags.IgnorePriorities ? IGNORE(gran_info) :
 588                            ID(gran_info);
 589
 590   if ( RtsFlags.GranFlags.SparkPriority!=0 &&
 591        pri<RtsFlags.GranFlags.SparkPriority ) {
 592     IF_GRAN_DEBUG(pri,
 593       debugBelch(",, NewSpark: Ignoring spark of priority %u (SparkPriority=%u); node=%#x; name=%u\n",
 594               pri, RtsFlags.GranFlags.SparkPriority, node, name));
 595     return ((rtsSpark*)NULL);
 596   }
 597
 598   newspark = (rtsSpark*) stgMallocBytes(sizeof(rtsSpark), "NewSpark");
 599   newspark->prev = newspark->next = (rtsSpark*)NULL;
 600   newspark->node = node;
 601   newspark->name = (name==1) ? CurrentTSO->gran.sparkname : name;
 602   newspark->gran_info = pri;
 603   newspark->global = !local;      /* Check that with parAt, parAtAbs !!*/
 604
 605   if (RtsFlags.GranFlags.GranSimStats.Global) {
 606     globalGranStats.tot_sparks_created++;
 607     globalGranStats.sparks_created_on_PE[CurrentProc]++;
 608   }
 609
 610   return(newspark);
 611 }
 612
 613 void
 614 disposeSpark(spark)
 615 rtsSpark *spark;
 616 {
 617   ASSERT(spark!=NULL);
 618   stgFree(spark);
 619 }
 620
 621 void
 622 disposeSparkQ(spark)
 623 rtsSparkQ spark;
 624 {
 625   if (spark==NULL)
 626     return;
 627
 628   disposeSparkQ(spark->next);
 629
 630 # ifdef GRAN_CHECK
 631   if (SparksAvail < 0) {
 632     debugBelch("disposeSparkQ: SparksAvail<0 after disposing sparkq @ %p\n", &spark);
 633     print_spark(spark);
 634   }
 635 # endif
 636
 637   stgFree(spark);
 638 }
 639
 640 /*
 641    With PrioritySparking add_to_spark_queue performs an insert sort to keep
 642    the spark queue sorted. Otherwise the spark is just added to the end of
 643    the queue.
 644 */
 645
 646 void
 647 add_to_spark_queue(spark)
 648 rtsSpark *spark;
 649 {
 650   rtsSpark *prev = NULL, *next = NULL;
 651   nat count = 0;
 652   rtsBool found = rtsFalse;
 653
 654   if ( spark == (rtsSpark *)NULL ) {
 655     return;
 656   }
 657
 658   if (RtsFlags.GranFlags.DoPrioritySparking && (spark->gran_info != 0) ) {
 659     /* Priority sparking is enabled i.e. spark queues must be sorted */
 660
 661     for (prev = NULL, next = pending_sparks_hd, count=0;
 662          (next != NULL) &&
 663          !(found = (spark->gran_info >= next->gran_info));
 664          prev = next, next = next->next, count++)
 665      {}
 666
 667   } else {   /* 'utQo' */
 668     /* Priority sparking is disabled */
 669
 670     found = rtsFalse;   /* to add it at the end */
 671
 672   }
 673
 674   if (found) {
 675     /* next points to the first spark with a gran_info smaller than that
 676        of spark; therefore, add spark before next into the spark queue */
 677     spark->next = next;
 678     if ( next == NULL ) {
 679       pending_sparks_tl = spark;
 680     } else {
 681       next->prev = spark;
 682     }
 683     spark->prev = prev;
 684     if ( prev == NULL ) {
 685       pending_sparks_hd = spark;
 686     } else {
 687       prev->next = spark;
 688     }
 689   } else {  /* (RtsFlags.GranFlags.DoPrioritySparking && !found) || !DoPrioritySparking */
 690     /* add the spark at the end of the spark queue */
 691     spark->next = NULL;
 692     spark->prev = pending_sparks_tl;
 693     if (pending_sparks_hd == NULL)
 694       pending_sparks_hd = spark;
 695     else
 696       pending_sparks_tl->next = spark;
 697     pending_sparks_tl = spark;
 698   }
 699   ++SparksAvail;
 700
 701   /* add costs for search in priority sparking */
 702   if (RtsFlags.GranFlags.DoPrioritySparking) {
 703     CurrentTime[CurrentProc] += count * RtsFlags.GranFlags.Costs.pri_spark_overhead;
 704   }
 705
 706   IF_GRAN_DEBUG(checkSparkQ,
 707                 debugBelch("++ Spark stats after adding spark %p (node %p) to queue on PE %d",
 708                       spark, spark->node, CurrentProc);
 709                 print_sparkq_stats());
 710
 711 #  if defined(GRAN_CHECK)
 712   if (RtsFlags.GranFlags.Debug.checkSparkQ) {
 713     for (prev = NULL, next =  pending_sparks_hd;
 714          (next != NULL);
 715          prev = next, next = next->next)
 716       {}
 717     if ( (prev!=NULL) && (prev!=pending_sparks_tl) )
 718       debugBelch("SparkQ inconsistency after adding spark %p: (PE %u) pending_sparks_tl (%p) not end of queue (%p)\n",
 719               spark,CurrentProc,
 720               pending_sparks_tl, prev);
 721   }
 722 #  endif
 723
 724 #  if defined(GRAN_CHECK)
 725   /* Check if the sparkq is still sorted. Just for testing, really!  */
 726   if ( RtsFlags.GranFlags.Debug.checkSparkQ &&
 727        RtsFlags.GranFlags.Debug.pri ) {
 728     rtsBool sorted = rtsTrue;
 729     rtsSpark *prev, *next;
 730
 731     if (pending_sparks_hd == NULL ||
 732         pending_sparks_hd->next == NULL ) {
 733       /* just 1 elem => ok */
 734     } else {
 735       for (prev = pending_sparks_hd,
 736            next = pending_sparks_hd->next;
 737            (next != NULL) ;
 738            prev = next, next = next->next) {
 739         sorted = sorted &&
 740                  (prev->gran_info >= next->gran_info);
 741       }
 742     }
 743     if (!sorted) {
 744       debugBelch("ghuH: SPARKQ on PE %d is not sorted:\n",
 745               CurrentProc);
 746       print_sparkq(CurrentProc);
 747     }
 748   }
 749 #  endif
 750 }
 751
 752 nat
 753 spark_queue_len(proc)
 754 PEs proc;
 755 {
 756  rtsSpark *prev, *spark;                     /* prev only for testing !! */
 757  nat len;
 758
 759  for (len = 0, prev = NULL, spark = pending_sparks_hds[proc];
 760       spark != NULL;
 761       len++, prev = spark, spark = spark->next)
 762    {}
 763
 764 #  if defined(GRAN_CHECK)
 765   if ( RtsFlags.GranFlags.Debug.checkSparkQ )
 766     if ( (prev!=NULL) && (prev!=pending_sparks_tls[proc]) )
 767       debugBelch("ERROR in spark_queue_len: (PE %u) pending_sparks_tl (%p) not end of queue (%p)\n",
 768               proc, pending_sparks_tls[proc], prev);
 769 #  endif
 770
 771  return (len);
 772 }
 773
 774 /*
 775    Take spark out of the spark queue on PE p and nuke the spark. Adjusts
 776    hd and tl pointers of the spark queue. Returns a pointer to the next
 777    spark in the queue.
 778 */
 779 rtsSpark *
 780 delete_from_sparkq (spark, p, dispose_too)     /* unlink and dispose spark */
 781 rtsSpark *spark;
 782 PEs p;
 783 rtsBool dispose_too;
 784 {
 785   rtsSpark *new_spark;
 786
 787   if (spark==NULL)
 788     barf("delete_from_sparkq: trying to delete NULL spark\n");
 789
 790 #  if defined(GRAN_CHECK)
 791   if ( RtsFlags.GranFlags.Debug.checkSparkQ ) {
 792     debugBelch("## |%p:%p| (%p)<-spark=%p->(%p) <-(%p)\n",
 793             pending_sparks_hd, pending_sparks_tl,
 794             spark->prev, spark, spark->next,
 795             (spark->next==NULL ? 0 : spark->next->prev));
 796   }
 797 #  endif
 798
 799   if (spark->prev==NULL) {
 800     /* spark is first spark of queue => adjust hd pointer */
 801     ASSERT(pending_sparks_hds[p]==spark);
 802     pending_sparks_hds[p] = spark->next;
 803   } else {
 804     spark->prev->next = spark->next;
 805   }
 806   if (spark->next==NULL) {
 807     ASSERT(pending_sparks_tls[p]==spark);
 808     /* spark is first spark of queue => adjust tl pointer */
 809     pending_sparks_tls[p] = spark->prev;
 810   } else {
 811     spark->next->prev = spark->prev;
 812   }
 813   new_spark = spark->next;
 814
 815 #  if defined(GRAN_CHECK)
 816   if ( RtsFlags.GranFlags.Debug.checkSparkQ ) {
 817     debugBelch("## |%p:%p| (%p)<-spark=%p->(%p) <-(%p); spark=%p will be deleted NOW \n",
 818             pending_sparks_hd, pending_sparks_tl,
 819             spark->prev, spark, spark->next,
 820             (spark->next==NULL ? 0 : spark->next->prev), spark);
 821   }
 822 #  endif
 823
 824   if (dispose_too)
 825     disposeSpark(spark);
 826
 827   return new_spark;
 828 }
 829
 830 /* Mark all nodes pointed to by sparks in the spark queues (for GC) */
 831 void
 832 markSparkQueue(void)
 833 {
 834   StgClosure *MarkRoot(StgClosure *root); // prototype
 835   PEs p;
 836   rtsSpark *sp;
 837
 838   for (p=0; p<RtsFlags.GranFlags.proc; p++)
 839     for (sp=pending_sparks_hds[p]; sp!=NULL; sp=sp->next) {
 840       ASSERT(sp->node!=NULL);
 841       ASSERT(LOOKS_LIKE_GHC_INFO(sp->node->header.info));
 842       // ToDo?: statistics gathering here (also for GUM!)
 843       sp->node = (StgClosure *)MarkRoot(sp->node);
 844     }
 845
 846   IF_DEBUG(gc,
 847            debugBelch("markSparkQueue: spark statistics at start of GC:");
 848            print_sparkq_stats());
 849 }
 850
 851 void
 852 print_spark(spark)
 853 rtsSpark *spark;
 854 {
 855   char str[16];
 856
 857   if (spark==NULL) {
 858     debugBelch("Spark: NIL\n");
 859     return;
 860   } else {
 861     sprintf(str,
 862             ((spark->node==NULL) ? "______" : "%#6lx"),
 863             stgCast(StgPtr,spark->node));
 864
 865     debugBelch("Spark: Node %8s, Name %#6x, Global %5s, Creator %5x, Prev %6p, Next %6p\n",
 866             str, spark->name,
 867             ((spark->global)==rtsTrue?"True":"False"), spark->creator,
 868             spark->prev, spark->next);
 869   }
 870 }
 871
 872 void
 873 print_sparkq(proc)
 874 PEs proc;
 875 // rtsSpark *hd;
 876 {
 877   rtsSpark *x = pending_sparks_hds[proc];
 878
 879   debugBelch("Spark Queue of PE %d with root at %p:\n", proc, x);
 880   for (; x!=(rtsSpark*)NULL; x=x->next) {
 881     print_spark(x);
 882   }
 883 }
 884
 885 /*
 886    Print a statistics of all spark queues.
 887 */
 888 void
 889 print_sparkq_stats(void)
 890 {
 891   PEs p;
 892
 893   debugBelch("SparkQs: [");
 894   for (p=0; p<RtsFlags.GranFlags.proc; p++)
 895     debugBelch(", PE %d: %d", p, spark_queue_len(p));
 896   debugBelch("\n");
 897 }
 898
 899 #endif