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annotate MasterLoop.c @ 182:7523ee70d66c

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author Nina Engelhardt <nengel@mailbox.tu-berlin.de>
date Fri, 06 Jan 2012 18:55:05 +0100
parents 3bd35fc83c61 c1784868dcea
children 50b29548d4f0
rev   line source
msach@94 1 /*
msach@94 2 * Copyright 2010 OpenSourceStewardshipFoundation
msach@94 3 *
msach@94 4 * Licensed under BSD
msach@94 5 */
msach@94 6
msach@94 7
msach@94 8
msach@94 9 #include <stdio.h>
msach@94 10 #include <stddef.h>
msach@94 11
msach@94 12 #include "VMS.h"
msach@94 13 #include "ProcrContext.h"
msach@94 14
msach@94 15
msach@94 16 //===========================================================================
msach@94 17 void inline
msach@94 18 stealWorkInto( SchedSlot *currSlot, VMSQueueStruc *readyToAnimateQ,
msach@94 19 VirtProcr *masterPr );
msach@94 20
msach@94 21 //===========================================================================
msach@94 22
msach@94 23
msach@94 24
msach@94 25 /*This code is animated by the virtual Master processor.
msach@94 26 *
msach@94 27 *Polls each sched slot exactly once, hands any requests made by a newly
msach@94 28 * done slave to the "request handler" plug-in function
msach@94 29 *
msach@94 30 *Any slots that need a virt procr assigned are given to the "schedule"
msach@94 31 * plug-in function, which tries to assign a virt procr (slave) to it.
msach@94 32 *
msach@94 33 *When all slots needing a processor have been given to the schedule plug-in,
msach@94 34 * a fraction of the procrs successfully scheduled are put into the
msach@94 35 * work queue, then a continuation of this function is put in, then the rest
msach@94 36 * of the virt procrs that were successfully scheduled.
msach@94 37 *
msach@94 38 *The first thing the continuation does is busy-wait until the previous
msach@94 39 * animation completes. This is because an (unlikely) continuation may
msach@94 40 * sneak through queue before previous continuation is done putting second
msach@94 41 * part of scheduled slaves in, which is the only race condition.
msach@94 42 *
msach@94 43 */
msach@94 44
msach@94 45 /*May 29, 2010 -- birth a Master during init so that first core loop to
msach@94 46 * start running gets it and does all the stuff for a newly born --
msach@94 47 * from then on, will be doing continuation, but do suspension self
msach@94 48 * directly at end of master loop
msach@94 49 *So VMS__init just births the master virtual processor same way it births
msach@94 50 * all the others -- then does any extra setup needed and puts it into the
msach@94 51 * work queue.
msach@94 52 *However means have to make masterEnv a global static volatile the same way
msach@94 53 * did with readyToAnimateQ in core loop. -- for performance, put the
msach@94 54 * jump to the core loop directly in here, and have it directly jump back.
msach@94 55 *
msach@94 56 *
msach@94 57 *Aug 18, 2010 -- Going to a separate MasterVP for each core, to see if this
msach@94 58 * avoids the suspected bug in the system stack that causes bizarre faults
msach@94 59 * at random places in the system code.
msach@94 60 *
msach@94 61 *So, this function is coupled to each of the MasterVPs, -- meaning this
msach@94 62 * function can't rely on a particular stack and frame -- each MasterVP that
msach@94 63 * animates this function has a different one.
msach@94 64 *
msach@94 65 *At this point, the masterLoop does not write itself into the queue anymore,
msach@94 66 * instead, the coreLoop acquires the masterLock when it has nothing to
msach@94 67 * animate, and then animates its own masterLoop. However, still try to put
msach@94 68 * several AppVPs into the queue to amortize the startup cost of switching
msach@94 69 * to the MasterVP. Note, don't have to worry about latency of requests much
msach@94 70 * because most requests generate work for same core -- only latency issue
msach@94 71 * is case when other cores starved and one core's requests generate work
msach@94 72 * for them -- so keep max in queue to 3 or 4..
msach@94 73 */
msach@94 74 void masterLoop( void *initData, VirtProcr *animatingPr )
msach@94 75 {
msach@94 76 int32 slotIdx, numSlotsFilled;
msach@94 77 VirtProcr *schedVirtPr;
msach@94 78 SchedSlot *currSlot, **schedSlots;
msach@94 79 MasterEnv *masterEnv;
msach@94 80 VMSQueueStruc *readyToAnimateQ;
msach@94 81
msach@94 82 SlaveScheduler slaveScheduler;
msach@94 83 RequestHandler requestHandler;
msach@94 84 void *semanticEnv;
msach@94 85
msach@94 86 int32 thisCoresIdx;
msach@94 87 VirtProcr *masterPr;
msach@94 88 volatile VirtProcr *volatileMasterPr;
msach@94 89
msach@94 90 volatileMasterPr = animatingPr;
msach@94 91 masterPr = (VirtProcr*)volatileMasterPr; //used to force re-define after jmp
msach@94 92
msach@94 93 //First animation of each MasterVP will in turn animate this part
msach@94 94 // of setup code.. (VP creator sets up the stack as if this function
msach@94 95 // was called normally, but actually get here by jmp)
msach@94 96 //So, setup values about stack ptr, jmp pt and all that
msach@94 97 //masterPr->nextInstrPt = &&masterLoopStartPt;
msach@94 98
msach@94 99
msach@94 100 //Note, got rid of writing the stack and frame ptr up here, because
msach@94 101 // only one
msach@94 102 // core can ever animate a given MasterVP, so don't need to communicate
msach@94 103 // new frame and stack ptr to the MasterVP storage before a second
msach@94 104 // version of that MasterVP can get animated on a different core.
msach@94 105 //Also got rid of the busy-wait.
msach@94 106
msach@94 107
msach@94 108 //masterLoopStartPt:
msach@94 109 while(1){
msach@94 110
msach@94 111 //============================= MEASUREMENT STUFF ========================
msach@94 112 #ifdef MEAS__TIME_MASTER
msach@94 113 //Total Master time includes one coreloop time -- just assume the core
msach@94 114 // loop time is same for Master as for AppVPs, even though it may be
msach@94 115 // smaller due to higher predictability of the fixed jmp.
msach@94 116 saveLowTimeStampCountInto( masterPr->startMasterTSCLow );
msach@94 117 #endif
msach@94 118 //========================================================================
msach@94 119
msach@94 120 masterEnv = (MasterEnv*)_VMSMasterEnv;
msach@94 121
msach@94 122 //GCC may optimize so doesn't always re-define from frame-storage
msach@94 123 masterPr = (VirtProcr*)volatileMasterPr; //just to make sure after jmp
msach@94 124 thisCoresIdx = masterPr->coreAnimatedBy;
msach@94 125 readyToAnimateQ = masterEnv->readyToAnimateQs[thisCoresIdx];
msach@94 126 schedSlots = masterEnv->allSchedSlots[thisCoresIdx];
msach@94 127
msach@94 128 requestHandler = masterEnv->requestHandler;
msach@94 129 slaveScheduler = masterEnv->slaveScheduler;
msach@94 130 semanticEnv = masterEnv->semanticEnv;
msach@94 131
msach@94 132
msach@94 133 //Poll each slot's Done flag
msach@94 134 numSlotsFilled = 0;
msach@94 135 for( slotIdx = 0; slotIdx < NUM_SCHED_SLOTS; slotIdx++)
msach@94 136 {
msach@94 137 currSlot = schedSlots[ slotIdx ];
msach@94 138
msach@94 139 if( currSlot->workIsDone )
msach@94 140 {
msach@94 141 currSlot->workIsDone = FALSE;
msach@94 142 currSlot->needsProcrAssigned = TRUE;
msach@94 143
msach@94 144 //process requests from slave to master
msach@94 145 //====================== MEASUREMENT STUFF ===================
msach@94 146 #ifdef MEAS__TIME_PLUGIN
msach@94 147 int32 startStamp1, endStamp1;
msach@94 148 saveLowTimeStampCountInto( startStamp1 );
msach@94 149 #endif
Nina@109 150 #ifdef MEAS__PERF_COUNTERS
engelhardt@108 151 int lastRecordIdx = currSlot->procrAssignedToSlot->counter_history_array_info->numInArray -1;
engelhardt@108 152 CounterRecord* lastRecord = currSlot->procrAssignedToSlot->counter_history[lastRecordIdx];
engelhardt@108 153 lastRecord->req_core = thisCoresIdx;
Nina@131 154 saveCyclesAndInstrs(thisCoresIdx,lastRecord->next_task_req_cycles,lastRecord->next_task_req_instrs);
engelhardt@108 155 //End of task, start of next task
engelhardt@108 156 //print counters from last run
Nina@131 157 addToDynArray((void*)lastRecord,masterEnv->counter_history_array_info);
Nina@110 158 print_record_csv_to_file(lastRecord,_VMSMasterEnv->counteroutput);
Nina@130 159
Nina@167 160
Nina@130 161
Nina@166 162
Nina@166 163
Nina@129 164 //print_record_human_readable(lastRecord);
Nina@109 165 //create new entry in record array
engelhardt@108 166 CounterRecord* newRecord = VMS__malloc(sizeof(CounterRecord));
engelhardt@108 167 newRecord->req_core = thisCoresIdx;
Nina@109 168 newRecord->vp_id = currSlot->procrAssignedToSlot->procrID;
Nina@111 169 newRecord->task_position = lastRecord->task_position + 1;
Nina@131 170 newRecord->req_cycles = lastRecord->next_task_req_cycles;
Nina@131 171 newRecord->req_instrs = lastRecord->next_task_req_instrs;
Nina@110 172 getReturnAddressBeforeLibraryCall(currSlot->procrAssignedToSlot, &(newRecord->addr_of_libcall_for_req));
engelhardt@108 173 addToDynArray( (void*) newRecord, currSlot->procrAssignedToSlot->counter_history_array_info);
engelhardt@108 174 lastRecord = newRecord;
engelhardt@108 175 #endif
msach@94 176 //============================================================
msach@94 177 (*requestHandler)( currSlot->procrAssignedToSlot, semanticEnv );
msach@94 178 //====================== MEASUREMENT STUFF ===================
msach@94 179 #ifdef MEAS__TIME_PLUGIN
msach@94 180 saveLowTimeStampCountInto( endStamp1 );
msach@94 181 addIntervalToHist( startStamp1, endStamp1,
msach@94 182 _VMSMasterEnv->reqHdlrLowTimeHist );
msach@94 183 addIntervalToHist( startStamp1, endStamp1,
msach@94 184 _VMSMasterEnv->reqHdlrHighTimeHist );
msach@94 185 #endif
Nina@109 186 #ifdef MEAS__PERF_COUNTERS
Nina@109 187 //done with constraints check
Nina@109 188 saveCyclesAndInstrs(thisCoresIdx,lastRecord->sc_done_cycles,lastRecord->sc_done_instrs);
Nina@109 189 saveLowTimeStampCountInto(lastRecord->blocked_timestamp);
engelhardt@108 190 #endif
msach@94 191 //============================================================
msach@94 192 }
msach@94 193 if( currSlot->needsProcrAssigned )
msach@94 194 { //give slot a new virt procr
Nina@109 195 #ifdef MEAS__PERF_COUNTERS
engelhardt@108 196 //start assigner
engelhardt@108 197 uint64 tmp_cycles;
engelhardt@108 198 uint64 tmp_instrs;
Nina@109 199 saveCyclesAndInstrs(thisCoresIdx,tmp_cycles,tmp_instrs);
engelhardt@108 200 #endif
msach@94 201 schedVirtPr =
nengel@177 202 (*slaveScheduler)( semanticEnv, thisCoresIdx, slotIdx );
Nina@109 203
msach@94 204 if( schedVirtPr != NULL )
msach@94 205 { currSlot->procrAssignedToSlot = schedVirtPr;
msach@94 206 schedVirtPr->schedSlot = currSlot;
msach@94 207 currSlot->needsProcrAssigned = FALSE;
msach@94 208 numSlotsFilled += 1;
nengel@177 209
Nina@109 210 #ifdef MEAS__PERF_COUNTERS
engelhardt@108 211 //end assigner
engelhardt@108 212 int lastRecordIdx = currSlot->procrAssignedToSlot->counter_history_array_info->numInArray -1;
engelhardt@108 213 CounterRecord* lastRecord = currSlot->procrAssignedToSlot->counter_history[lastRecordIdx];
engelhardt@108 214 lastRecord->assigning_core = thisCoresIdx;
engelhardt@108 215 lastRecord->start_assign_cycles = tmp_cycles;
engelhardt@108 216 lastRecord->start_assign_instrs = tmp_instrs;
Nina@109 217 saveCyclesAndInstrs(thisCoresIdx,lastRecord->end_assign_cycles,lastRecord->end_assign_instrs);
engelhardt@108 218 #endif
nengel@177 219
msach@94 220 writeVMSQ( schedVirtPr, readyToAnimateQ );
msach@94 221 }
msach@94 222 }
nengel@177 223
msach@94 224 }
msach@94 225
msach@94 226
msach@94 227 #ifdef USE_WORK_STEALING
msach@94 228 //If no slots filled, means no more work, look for work to steal.
msach@94 229 if( numSlotsFilled == 0 )
msach@94 230 { gateProtected_stealWorkInto( currSlot, readyToAnimateQ, masterPr );
msach@94 231 }
msach@94 232 #endif
msach@94 233
msach@94 234
msach@94 235 #ifdef MEAS__TIME_MASTER
msach@94 236 saveLowTimeStampCountInto( masterPr->endMasterTSCLow );
msach@94 237 #endif
msach@94 238
msach@94 239 masterSwitchToCoreLoop(animatingPr);
msach@94 240 flushRegisters();
msach@94 241 }//MasterLoop
msach@94 242
msach@94 243
msach@94 244 }
msach@94 245
msach@94 246
msach@94 247
msach@94 248 /*This has a race condition -- the coreloops are accessing their own queues
msach@94 249 * at the same time that this work-stealer on a different core is trying to
msach@94 250 */
msach@94 251 void inline
msach@94 252 stealWorkInto( SchedSlot *currSlot, VMSQueueStruc *readyToAnimateQ,
msach@94 253 VirtProcr *masterPr )
msach@94 254 {
msach@94 255 VirtProcr *stolenPr;
msach@94 256 int32 coreIdx, i;
msach@94 257 VMSQueueStruc *currQ;
msach@94 258
msach@94 259 stolenPr = NULL;
msach@94 260 coreIdx = masterPr->coreAnimatedBy;
msach@94 261 for( i = 0; i < NUM_CORES -1; i++ )
msach@94 262 {
msach@94 263 if( coreIdx >= NUM_CORES -1 )
msach@94 264 { coreIdx = 0;
msach@94 265 }
msach@94 266 else
msach@94 267 { coreIdx++;
msach@94 268 }
msach@94 269 currQ = _VMSMasterEnv->readyToAnimateQs[coreIdx];
msach@94 270 if( numInVMSQ( currQ ) > 0 )
msach@94 271 { stolenPr = readVMSQ (currQ );
msach@94 272 break;
msach@94 273 }
msach@94 274 }
msach@94 275
msach@94 276 if( stolenPr != NULL )
msach@94 277 { currSlot->procrAssignedToSlot = stolenPr;
msach@94 278 stolenPr->schedSlot = currSlot;
msach@94 279 currSlot->needsProcrAssigned = FALSE;
msach@94 280
msach@94 281 writeVMSQ( stolenPr, readyToAnimateQ );
msach@94 282 }
msach@94 283 }
msach@94 284
msach@94 285 /*This algorithm makes the common case fast. Make the coreloop passive,
msach@94 286 * and show its progress. Make the stealer control a gate that coreloop
msach@94 287 * has to pass.
msach@94 288 *To avoid interference, only one stealer at a time. Use a global
msach@94 289 * stealer-lock.
msach@94 290 *
msach@94 291 *The pattern is based on a gate -- stealer shuts the gate, then monitors
msach@94 292 * to be sure any already past make it all the way out, before starting.
msach@94 293 *So, have a "progress" measure just before the gate, then have two after it,
msach@94 294 * one is in a "waiting room" outside the gate, the other is at the exit.
msach@94 295 *Then, the stealer first shuts the gate, then checks the progress measure
msach@94 296 * outside it, then looks to see if the progress measure at the exit is the
msach@94 297 * same. If yes, it knows the protected area is empty 'cause no other way
msach@94 298 * to get in and the last to get in also exited.
msach@94 299 *If the progress measure at the exit is not the same, then the stealer goes
msach@94 300 * into a loop checking both the waiting-area and the exit progress-measures
msach@94 301 * until one of them shows the same as the measure outside the gate. Might
msach@94 302 * as well re-read the measure outside the gate each go around, just to be
msach@94 303 * sure. It is guaranteed that one of the two will eventually match the one
msach@94 304 * outside the gate.
msach@94 305 *
msach@94 306 *Here's an informal proof of correctness:
msach@94 307 *The gate can be closed at any point, and have only four cases:
msach@94 308 * 1) coreloop made it past the gate-closing but not yet past the exit
msach@94 309 * 2) coreloop made it past the pre-gate progress update but not yet past
msach@94 310 * the gate,
msach@94 311 * 3) coreloop is right before the pre-gate update
msach@94 312 * 4) coreloop is past the exit and far from the pre-gate update.
msach@94 313 *
msach@94 314 * Covering the cases in reverse order,
msach@94 315 * 4) is not a problem -- stealer will read pre-gate progress, see that it
msach@94 316 * matches exit progress, and the gate is closed, so stealer can proceed.
msach@94 317 * 3) stealer will read pre-gate progress just after coreloop updates it..
msach@94 318 * so stealer goes into a loop until the coreloop causes wait-progress
msach@94 319 * to match pre-gate progress, so then stealer can proceed
msach@94 320 * 2) same as 3..
msach@94 321 * 1) stealer reads pre-gate progress, sees that it's different than exit,
msach@94 322 * so goes into loop until exit matches pre-gate, now it knows coreloop
msach@94 323 * is not in protected and cannot get back in, so can proceed.
msach@94 324 *
msach@94 325 *Implementation for the stealer:
msach@94 326 *
msach@94 327 *First, acquire the stealer lock -- only cores with no work to do will
msach@94 328 * compete to steal, so not a big performance penalty having only one --
msach@94 329 * will rarely have multiple stealers in a system with plenty of work -- and
msach@94 330 * in a system with little work, it doesn't matter.
msach@94 331 *
msach@94 332 *Note, have single-reader, single-writer pattern for all variables used to
msach@94 333 * communicate between stealer and victims
msach@94 334 *
msach@94 335 *So, scan the queues of the core loops, until find non-empty. Each core
msach@94 336 * has its own list that it scans. The list goes in order from closest to
msach@94 337 * furthest core, so it steals first from close cores. Later can add
msach@94 338 * taking info from the app about overlapping footprints, and scan all the
msach@94 339 * others then choose work with the most footprint overlap with the contents
msach@94 340 * of this core's cache.
msach@94 341 *
msach@94 342 *Now, have a victim want to take work from. So, shut the gate in that
msach@94 343 * coreloop, by setting the "gate closed" var on its stack to TRUE.
msach@94 344 *Then, read the core's pre-gate progress and compare to the core's exit
msach@94 345 * progress.
msach@94 346 *If same, can proceed to take work from the coreloop's queue. When done,
msach@94 347 * write FALSE to gate closed var.
msach@94 348 *If different, then enter a loop that reads the pre-gate progress, then
msach@94 349 * compares to exit progress then to wait progress. When one of two
msach@94 350 * matches, proceed. Take work from the coreloop's queue. When done,
msach@94 351 * write FALSE to the gate closed var.
msach@94 352 *
msach@94 353 */
msach@94 354 void inline
msach@94 355 gateProtected_stealWorkInto( SchedSlot *currSlot,
msach@94 356 VMSQueueStruc *myReadyToAnimateQ,
msach@94 357 VirtProcr *masterPr )
msach@94 358 {
msach@94 359 VirtProcr *stolenPr;
msach@94 360 int32 coreIdx, i, haveAVictim, gotLock;
msach@94 361 VMSQueueStruc *victimsQ;
msach@94 362
msach@94 363 volatile GateStruc *vicGate;
msach@94 364 int32 coreMightBeInProtected;
msach@94 365
msach@94 366
msach@94 367
msach@94 368 //see if any other cores have work available to steal
msach@94 369 haveAVictim = FALSE;
msach@94 370 coreIdx = masterPr->coreAnimatedBy;
msach@94 371 for( i = 0; i < NUM_CORES -1; i++ )
msach@94 372 {
msach@94 373 if( coreIdx >= NUM_CORES -1 )
msach@94 374 { coreIdx = 0;
msach@94 375 }
msach@94 376 else
msach@94 377 { coreIdx++;
msach@94 378 }
msach@94 379 victimsQ = _VMSMasterEnv->readyToAnimateQs[coreIdx];
msach@94 380 if( numInVMSQ( victimsQ ) > 0 )
msach@94 381 { haveAVictim = TRUE;
msach@94 382 vicGate = _VMSMasterEnv->workStealingGates[ coreIdx ];
msach@94 383 break;
msach@94 384 }
msach@94 385 }
msach@94 386 if( !haveAVictim ) return; //no work to steal, exit
msach@94 387
msach@94 388 //have a victim core, now get the stealer-lock
msach@94 389 gotLock =__sync_bool_compare_and_swap( &(_VMSMasterEnv->workStealingLock),
msach@94 390 UNLOCKED, LOCKED );
msach@94 391 if( !gotLock ) return; //go back to core loop, which will re-start master
msach@94 392
msach@94 393
msach@94 394 //====== Start Gate-protection =======
msach@94 395 vicGate->gateClosed = TRUE;
msach@94 396 coreMightBeInProtected= vicGate->preGateProgress != vicGate->exitProgress;
msach@94 397 while( coreMightBeInProtected )
msach@94 398 { //wait until sure
msach@94 399 if( vicGate->preGateProgress == vicGate->waitProgress )
msach@94 400 coreMightBeInProtected = FALSE;
msach@94 401 if( vicGate->preGateProgress == vicGate->exitProgress )
msach@94 402 coreMightBeInProtected = FALSE;
msach@94 403 }
msach@94 404
msach@94 405 stolenPr = readVMSQ ( victimsQ );
msach@94 406
msach@94 407 vicGate->gateClosed = FALSE;
msach@94 408 //======= End Gate-protection =======
msach@94 409
msach@94 410
msach@94 411 if( stolenPr != NULL ) //victim could have been in protected and taken
msach@94 412 { currSlot->procrAssignedToSlot = stolenPr;
msach@94 413 stolenPr->schedSlot = currSlot;
msach@94 414 currSlot->needsProcrAssigned = FALSE;
msach@94 415
msach@94 416 writeVMSQ( stolenPr, myReadyToAnimateQ );
msach@94 417 }
msach@94 418
msach@94 419 //unlock the work stealing lock
msach@94 420 _VMSMasterEnv->workStealingLock = UNLOCKED;
msach@94 421 }