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annotate MasterLoop.c @ 211:5b419522dc7f

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author Nina Engelhardt <nengel@mailbox.tu-berlin.de>
date Thu, 08 Mar 2012 19:02:16 +0100
parents 20358f56e498
children
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
nengel@211 92 int vpid,task;
msach@94 93
msach@94 94 //First animation of each MasterVP will in turn animate this part
msach@94 95 // of setup code.. (VP creator sets up the stack as if this function
msach@94 96 // was called normally, but actually get here by jmp)
msach@94 97 //So, setup values about stack ptr, jmp pt and all that
msach@94 98 //masterPr->nextInstrPt = &&masterLoopStartPt;
msach@94 99
msach@94 100
msach@94 101 //Note, got rid of writing the stack and frame ptr up here, because
msach@94 102 // only one
msach@94 103 // core can ever animate a given MasterVP, so don't need to communicate
msach@94 104 // new frame and stack ptr to the MasterVP storage before a second
msach@94 105 // version of that MasterVP can get animated on a different core.
msach@94 106 //Also got rid of the busy-wait.
msach@94 107
msach@94 108
msach@94 109 //masterLoopStartPt:
msach@94 110 while(1){
msach@94 111
msach@94 112 //============================= MEASUREMENT STUFF ========================
msach@94 113 #ifdef MEAS__TIME_MASTER
msach@94 114 //Total Master time includes one coreloop time -- just assume the core
msach@94 115 // loop time is same for Master as for AppVPs, even though it may be
msach@94 116 // smaller due to higher predictability of the fixed jmp.
msach@94 117 saveLowTimeStampCountInto( masterPr->startMasterTSCLow );
msach@94 118 #endif
nengel@186 119
msach@94 120 //========================================================================
msach@94 121
msach@94 122 masterEnv = (MasterEnv*)_VMSMasterEnv;
msach@94 123
msach@94 124 //GCC may optimize so doesn't always re-define from frame-storage
msach@94 125 masterPr = (VirtProcr*)volatileMasterPr; //just to make sure after jmp
msach@94 126 thisCoresIdx = masterPr->coreAnimatedBy;
msach@94 127 readyToAnimateQ = masterEnv->readyToAnimateQs[thisCoresIdx];
msach@94 128 schedSlots = masterEnv->allSchedSlots[thisCoresIdx];
msach@94 129
msach@94 130 requestHandler = masterEnv->requestHandler;
msach@94 131 slaveScheduler = masterEnv->slaveScheduler;
msach@94 132 semanticEnv = masterEnv->semanticEnv;
nengel@184 133
nengel@186 134 #ifdef MEAS__PERF_COUNTERS
nengel@186 135 CounterHandler counterHandler = masterEnv->counterHandler;
nengel@186 136 #endif
nengel@193 137 //
msach@94 138 //Poll each slot's Done flag
msach@94 139 numSlotsFilled = 0;
msach@94 140 for( slotIdx = 0; slotIdx < NUM_SCHED_SLOTS; slotIdx++)
msach@94 141 {
msach@94 142 currSlot = schedSlots[ slotIdx ];
msach@94 143
msach@94 144 if( currSlot->workIsDone )
msach@94 145 {
msach@94 146 currSlot->workIsDone = FALSE;
msach@94 147 currSlot->needsProcrAssigned = TRUE;
msach@94 148
msach@94 149 //process requests from slave to master
msach@94 150 //====================== MEASUREMENT STUFF ===================
msach@94 151 #ifdef MEAS__TIME_PLUGIN
msach@94 152 int32 startStamp1, endStamp1;
msach@94 153 saveLowTimeStampCountInto( startStamp1 );
msach@94 154 #endif
Nina@109 155 #ifdef MEAS__PERF_COUNTERS
nengel@211 156 /* Request Handler may call resume() on the VP, but we want to
nengel@211 157 * account the whole interval to the same task. Therefore, need
nengel@211 158 * to save task ID at the beginning.
nengel@211 159 *
nengel@211 160 * Using this value as "end of AppResponder Invocation Time"
nengel@211 161 * is possible if there is only one SchedSlot per core -
nengel@211 162 * invoking processor is last to be treated here! If more than
nengel@211 163 * one slot, MasterLoop processing time for all but the last VP
nengel@211 164 * would be erroneously counted as invocation time.
nengel@211 165 */
nengel@211 166 vpid = currSlot->procrAssignedToSlot->procrID;
nengel@211 167 task = currSlot->procrAssignedToSlot->numTimesScheduled;
nengel@185 168 uint64 cycles, instrs;
nengel@184 169 saveCyclesAndInstrs(thisCoresIdx,cycles, instrs);
nengel@193 170 (*counterHandler)(AppResponder_start,vpid,task,currSlot->procrAssignedToSlot,cycles,instrs);
engelhardt@108 171 #endif
msach@94 172 //============================================================
msach@94 173 (*requestHandler)( currSlot->procrAssignedToSlot, semanticEnv );
msach@94 174 //====================== MEASUREMENT STUFF ===================
msach@94 175 #ifdef MEAS__TIME_PLUGIN
msach@94 176 saveLowTimeStampCountInto( endStamp1 );
msach@94 177 addIntervalToHist( startStamp1, endStamp1,
msach@94 178 _VMSMasterEnv->reqHdlrLowTimeHist );
msach@94 179 addIntervalToHist( startStamp1, endStamp1,
msach@94 180 _VMSMasterEnv->reqHdlrHighTimeHist );
msach@94 181 #endif
Nina@109 182 #ifdef MEAS__PERF_COUNTERS
nengel@211 183 //use previous task ID here (may or may not be the same as current VP state)
nengel@185 184 uint64 cycles2,instrs2;
nengel@185 185 saveCyclesAndInstrs(thisCoresIdx,cycles2, instrs2);
nengel@193 186 (*counterHandler)(AppResponder_end,vpid,task,currSlot->procrAssignedToSlot,cycles2,instrs2);
nengel@211 187 (*counterHandler)(Timestamp_end,vpid,task,currSlot->procrAssignedToSlot,rdtsc(),0);
engelhardt@108 188 #endif
msach@94 189 //============================================================
msach@94 190 }
msach@94 191 if( currSlot->needsProcrAssigned )
msach@94 192 { //give slot a new virt procr
Nina@109 193 #ifdef MEAS__PERF_COUNTERS
engelhardt@108 194 //start assigner
nengel@211 195 /* Don't know who to account time to yet - goes to assigned VP
nengel@211 196 * after the call.
nengel@211 197 */
nengel@211 198 int empty = FALSE;
nengel@211 199 if(currSlot->procrAssignedToSlot == NULL){
nengel@211 200 empty= TRUE;
nengel@211 201 }
engelhardt@108 202 uint64 tmp_cycles;
engelhardt@108 203 uint64 tmp_instrs;
Nina@109 204 saveCyclesAndInstrs(thisCoresIdx,tmp_cycles,tmp_instrs);
nengel@211 205 uint64 tsc = rdtsc();
nengel@211 206 if(vpid > 0) {
nengel@211 207 (*counterHandler)(NextAssigner_start,vpid,task,currSlot->procrAssignedToSlot,tmp_cycles,tmp_instrs);
nengel@211 208 vpid = 0;
nengel@211 209 task = 0;
nengel@211 210 }
engelhardt@108 211 #endif
msach@94 212 schedVirtPr =
nengel@177 213 (*slaveScheduler)( semanticEnv, thisCoresIdx, slotIdx );
Nina@109 214
msach@94 215 if( schedVirtPr != NULL )
msach@94 216 { currSlot->procrAssignedToSlot = schedVirtPr;
msach@94 217 schedVirtPr->schedSlot = currSlot;
msach@94 218 currSlot->needsProcrAssigned = FALSE;
msach@94 219 numSlotsFilled += 1;
nengel@177 220
nengel@185 221 writeVMSQ( schedVirtPr, readyToAnimateQ );
nengel@185 222
Nina@109 223 #ifdef MEAS__PERF_COUNTERS
nengel@184 224 uint64 cycles;
nengel@184 225 uint64 instrs;
nengel@184 226 saveCyclesAndInstrs(thisCoresIdx,cycles,instrs);
nengel@211 227
nengel@211 228 if(empty){
nengel@211 229 (*counterHandler)(AssignerInvocation_start,schedVirtPr->procrID,schedVirtPr->numTimesScheduled,schedVirtPr,masterEnv->start_master_lock[thisCoresIdx][0],masterEnv->start_master_lock[thisCoresIdx][1]);
nengel@211 230 }
nengel@211 231 (*counterHandler)(Timestamp_start,schedVirtPr->procrID,schedVirtPr->numTimesScheduled,schedVirtPr,tsc,0);
nengel@193 232 (*counterHandler)(Assigner_start,schedVirtPr->procrID,schedVirtPr->numTimesScheduled,schedVirtPr,tmp_cycles,tmp_instrs);
nengel@193 233 (*counterHandler)(Assigner_end,schedVirtPr->procrID,schedVirtPr->numTimesScheduled,schedVirtPr,cycles,instrs);
engelhardt@108 234 #endif
msach@94 235 }
msach@94 236 }
nengel@177 237
msach@94 238 }
msach@94 239
msach@94 240
msach@94 241 #ifdef USE_WORK_STEALING
msach@94 242 //If no slots filled, means no more work, look for work to steal.
msach@94 243 if( numSlotsFilled == 0 )
msach@94 244 { gateProtected_stealWorkInto( currSlot, readyToAnimateQ, masterPr );
msach@94 245 }
msach@94 246 #endif
msach@94 247
msach@94 248
msach@94 249 #ifdef MEAS__TIME_MASTER
msach@94 250 saveLowTimeStampCountInto( masterPr->endMasterTSCLow );
msach@94 251 #endif
msach@94 252
msach@94 253 masterSwitchToCoreLoop(animatingPr);
msach@94 254 flushRegisters();
msach@94 255 }//MasterLoop
msach@94 256
msach@94 257
msach@94 258 }
msach@94 259
msach@94 260
msach@94 261
msach@94 262 /*This has a race condition -- the coreloops are accessing their own queues
msach@94 263 * at the same time that this work-stealer on a different core is trying to
msach@94 264 */
msach@94 265 void inline
msach@94 266 stealWorkInto( SchedSlot *currSlot, VMSQueueStruc *readyToAnimateQ,
msach@94 267 VirtProcr *masterPr )
msach@94 268 {
msach@94 269 VirtProcr *stolenPr;
msach@94 270 int32 coreIdx, i;
msach@94 271 VMSQueueStruc *currQ;
msach@94 272
msach@94 273 stolenPr = NULL;
msach@94 274 coreIdx = masterPr->coreAnimatedBy;
msach@94 275 for( i = 0; i < NUM_CORES -1; i++ )
msach@94 276 {
msach@94 277 if( coreIdx >= NUM_CORES -1 )
msach@94 278 { coreIdx = 0;
msach@94 279 }
msach@94 280 else
msach@94 281 { coreIdx++;
msach@94 282 }
msach@94 283 currQ = _VMSMasterEnv->readyToAnimateQs[coreIdx];
msach@94 284 if( numInVMSQ( currQ ) > 0 )
msach@94 285 { stolenPr = readVMSQ (currQ );
msach@94 286 break;
msach@94 287 }
msach@94 288 }
msach@94 289
msach@94 290 if( stolenPr != NULL )
msach@94 291 { currSlot->procrAssignedToSlot = stolenPr;
msach@94 292 stolenPr->schedSlot = currSlot;
msach@94 293 currSlot->needsProcrAssigned = FALSE;
msach@94 294
msach@94 295 writeVMSQ( stolenPr, readyToAnimateQ );
msach@94 296 }
msach@94 297 }
msach@94 298
msach@94 299 /*This algorithm makes the common case fast. Make the coreloop passive,
msach@94 300 * and show its progress. Make the stealer control a gate that coreloop
msach@94 301 * has to pass.
msach@94 302 *To avoid interference, only one stealer at a time. Use a global
msach@94 303 * stealer-lock.
msach@94 304 *
msach@94 305 *The pattern is based on a gate -- stealer shuts the gate, then monitors
msach@94 306 * to be sure any already past make it all the way out, before starting.
msach@94 307 *So, have a "progress" measure just before the gate, then have two after it,
msach@94 308 * one is in a "waiting room" outside the gate, the other is at the exit.
msach@94 309 *Then, the stealer first shuts the gate, then checks the progress measure
msach@94 310 * outside it, then looks to see if the progress measure at the exit is the
msach@94 311 * same. If yes, it knows the protected area is empty 'cause no other way
msach@94 312 * to get in and the last to get in also exited.
msach@94 313 *If the progress measure at the exit is not the same, then the stealer goes
msach@94 314 * into a loop checking both the waiting-area and the exit progress-measures
msach@94 315 * until one of them shows the same as the measure outside the gate. Might
msach@94 316 * as well re-read the measure outside the gate each go around, just to be
msach@94 317 * sure. It is guaranteed that one of the two will eventually match the one
msach@94 318 * outside the gate.
msach@94 319 *
msach@94 320 *Here's an informal proof of correctness:
msach@94 321 *The gate can be closed at any point, and have only four cases:
msach@94 322 * 1) coreloop made it past the gate-closing but not yet past the exit
msach@94 323 * 2) coreloop made it past the pre-gate progress update but not yet past
msach@94 324 * the gate,
msach@94 325 * 3) coreloop is right before the pre-gate update
msach@94 326 * 4) coreloop is past the exit and far from the pre-gate update.
msach@94 327 *
msach@94 328 * Covering the cases in reverse order,
msach@94 329 * 4) is not a problem -- stealer will read pre-gate progress, see that it
msach@94 330 * matches exit progress, and the gate is closed, so stealer can proceed.
msach@94 331 * 3) stealer will read pre-gate progress just after coreloop updates it..
msach@94 332 * so stealer goes into a loop until the coreloop causes wait-progress
msach@94 333 * to match pre-gate progress, so then stealer can proceed
msach@94 334 * 2) same as 3..
msach@94 335 * 1) stealer reads pre-gate progress, sees that it's different than exit,
msach@94 336 * so goes into loop until exit matches pre-gate, now it knows coreloop
msach@94 337 * is not in protected and cannot get back in, so can proceed.
msach@94 338 *
msach@94 339 *Implementation for the stealer:
msach@94 340 *
msach@94 341 *First, acquire the stealer lock -- only cores with no work to do will
msach@94 342 * compete to steal, so not a big performance penalty having only one --
msach@94 343 * will rarely have multiple stealers in a system with plenty of work -- and
msach@94 344 * in a system with little work, it doesn't matter.
msach@94 345 *
msach@94 346 *Note, have single-reader, single-writer pattern for all variables used to
msach@94 347 * communicate between stealer and victims
msach@94 348 *
msach@94 349 *So, scan the queues of the core loops, until find non-empty. Each core
msach@94 350 * has its own list that it scans. The list goes in order from closest to
msach@94 351 * furthest core, so it steals first from close cores. Later can add
msach@94 352 * taking info from the app about overlapping footprints, and scan all the
msach@94 353 * others then choose work with the most footprint overlap with the contents
msach@94 354 * of this core's cache.
msach@94 355 *
msach@94 356 *Now, have a victim want to take work from. So, shut the gate in that
msach@94 357 * coreloop, by setting the "gate closed" var on its stack to TRUE.
msach@94 358 *Then, read the core's pre-gate progress and compare to the core's exit
msach@94 359 * progress.
msach@94 360 *If same, can proceed to take work from the coreloop's queue. When done,
msach@94 361 * write FALSE to gate closed var.
msach@94 362 *If different, then enter a loop that reads the pre-gate progress, then
msach@94 363 * compares to exit progress then to wait progress. When one of two
msach@94 364 * matches, proceed. Take work from the coreloop's queue. When done,
msach@94 365 * write FALSE to the gate closed var.
msach@94 366 *
msach@94 367 */
msach@94 368 void inline
msach@94 369 gateProtected_stealWorkInto( SchedSlot *currSlot,
msach@94 370 VMSQueueStruc *myReadyToAnimateQ,
msach@94 371 VirtProcr *masterPr )
msach@94 372 {
msach@94 373 VirtProcr *stolenPr;
msach@94 374 int32 coreIdx, i, haveAVictim, gotLock;
msach@94 375 VMSQueueStruc *victimsQ;
msach@94 376
msach@94 377 volatile GateStruc *vicGate;
msach@94 378 int32 coreMightBeInProtected;
msach@94 379
msach@94 380
msach@94 381
msach@94 382 //see if any other cores have work available to steal
msach@94 383 haveAVictim = FALSE;
msach@94 384 coreIdx = masterPr->coreAnimatedBy;
msach@94 385 for( i = 0; i < NUM_CORES -1; i++ )
msach@94 386 {
msach@94 387 if( coreIdx >= NUM_CORES -1 )
msach@94 388 { coreIdx = 0;
msach@94 389 }
msach@94 390 else
msach@94 391 { coreIdx++;
msach@94 392 }
msach@94 393 victimsQ = _VMSMasterEnv->readyToAnimateQs[coreIdx];
msach@94 394 if( numInVMSQ( victimsQ ) > 0 )
msach@94 395 { haveAVictim = TRUE;
msach@94 396 vicGate = _VMSMasterEnv->workStealingGates[ coreIdx ];
msach@94 397 break;
msach@94 398 }
msach@94 399 }
msach@94 400 if( !haveAVictim ) return; //no work to steal, exit
msach@94 401
msach@94 402 //have a victim core, now get the stealer-lock
msach@94 403 gotLock =__sync_bool_compare_and_swap( &(_VMSMasterEnv->workStealingLock),
msach@94 404 UNLOCKED, LOCKED );
msach@94 405 if( !gotLock ) return; //go back to core loop, which will re-start master
msach@94 406
msach@94 407
msach@94 408 //====== Start Gate-protection =======
msach@94 409 vicGate->gateClosed = TRUE;
msach@94 410 coreMightBeInProtected= vicGate->preGateProgress != vicGate->exitProgress;
msach@94 411 while( coreMightBeInProtected )
msach@94 412 { //wait until sure
msach@94 413 if( vicGate->preGateProgress == vicGate->waitProgress )
msach@94 414 coreMightBeInProtected = FALSE;
msach@94 415 if( vicGate->preGateProgress == vicGate->exitProgress )
msach@94 416 coreMightBeInProtected = FALSE;
msach@94 417 }
msach@94 418
msach@94 419 stolenPr = readVMSQ ( victimsQ );
msach@94 420
msach@94 421 vicGate->gateClosed = FALSE;
msach@94 422 //======= End Gate-protection =======
msach@94 423
msach@94 424
msach@94 425 if( stolenPr != NULL ) //victim could have been in protected and taken
msach@94 426 { currSlot->procrAssignedToSlot = stolenPr;
msach@94 427 stolenPr->schedSlot = currSlot;
msach@94 428 currSlot->needsProcrAssigned = FALSE;
msach@94 429
msach@94 430 writeVMSQ( stolenPr, myReadyToAnimateQ );
msach@94 431 }
msach@94 432
msach@94 433 //unlock the work stealing lock
msach@94 434 _VMSMasterEnv->workStealingLock = UNLOCKED;
msach@94 435 }