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annotate MasterLoop.c @ 185:28cc465f7eb7

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new counter interface works now
author Nina Engelhardt <nengel@mailbox.tu-berlin.de>
date Fri, 13 Jan 2012 18:34:31 +0100
parents 50b29548d4f0
children 69eb54ce9c4b
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;
nengel@184 131
nengel@184 132 #ifdef MEAS__PERF_COUNTERS
nengel@185 133 CounterHandler counterHandler = masterEnv->counterHandler;
nengel@184 134 #endif
msach@94 135
msach@94 136 //Poll each slot's Done flag
msach@94 137 numSlotsFilled = 0;
msach@94 138 for( slotIdx = 0; slotIdx < NUM_SCHED_SLOTS; slotIdx++)
msach@94 139 {
msach@94 140 currSlot = schedSlots[ slotIdx ];
msach@94 141
msach@94 142 if( currSlot->workIsDone )
msach@94 143 {
msach@94 144 currSlot->workIsDone = FALSE;
msach@94 145 currSlot->needsProcrAssigned = TRUE;
msach@94 146
msach@94 147 //process requests from slave to master
msach@94 148 //====================== MEASUREMENT STUFF ===================
msach@94 149 #ifdef MEAS__TIME_PLUGIN
msach@94 150 int32 startStamp1, endStamp1;
msach@94 151 saveLowTimeStampCountInto( startStamp1 );
msach@94 152 #endif
Nina@109 153 #ifdef MEAS__PERF_COUNTERS
nengel@185 154 uint64 cycles, instrs;
nengel@184 155 saveCyclesAndInstrs(thisCoresIdx,cycles, instrs);
nengel@185 156 (*counterHandler)(MasterLoop_beforeReqHdlr,currSlot->procrAssignedToSlot,cycles,instrs);
engelhardt@108 157 #endif
msach@94 158 //============================================================
msach@94 159 (*requestHandler)( currSlot->procrAssignedToSlot, semanticEnv );
msach@94 160 //====================== MEASUREMENT STUFF ===================
msach@94 161 #ifdef MEAS__TIME_PLUGIN
msach@94 162 saveLowTimeStampCountInto( endStamp1 );
msach@94 163 addIntervalToHist( startStamp1, endStamp1,
msach@94 164 _VMSMasterEnv->reqHdlrLowTimeHist );
msach@94 165 addIntervalToHist( startStamp1, endStamp1,
msach@94 166 _VMSMasterEnv->reqHdlrHighTimeHist );
msach@94 167 #endif
Nina@109 168 #ifdef MEAS__PERF_COUNTERS
Nina@109 169 //done with constraints check
nengel@185 170 uint64 cycles2,instrs2;
nengel@185 171 saveCyclesAndInstrs(thisCoresIdx,cycles2, instrs2);
nengel@185 172 (*counterHandler)(MasterLoop_afterReqHdlr,currSlot->procrAssignedToSlot,cycles2,instrs2);
engelhardt@108 173 #endif
msach@94 174 //============================================================
msach@94 175 }
msach@94 176 if( currSlot->needsProcrAssigned )
msach@94 177 { //give slot a new virt procr
Nina@109 178 #ifdef MEAS__PERF_COUNTERS
engelhardt@108 179 //start assigner
engelhardt@108 180 uint64 tmp_cycles;
engelhardt@108 181 uint64 tmp_instrs;
Nina@109 182 saveCyclesAndInstrs(thisCoresIdx,tmp_cycles,tmp_instrs);
engelhardt@108 183 #endif
msach@94 184 schedVirtPr =
nengel@177 185 (*slaveScheduler)( semanticEnv, thisCoresIdx, slotIdx );
Nina@109 186
msach@94 187 if( schedVirtPr != NULL )
msach@94 188 { currSlot->procrAssignedToSlot = schedVirtPr;
msach@94 189 schedVirtPr->schedSlot = currSlot;
msach@94 190 currSlot->needsProcrAssigned = FALSE;
msach@94 191 numSlotsFilled += 1;
nengel@177 192
nengel@185 193 writeVMSQ( schedVirtPr, readyToAnimateQ );
nengel@185 194
Nina@109 195 #ifdef MEAS__PERF_COUNTERS
nengel@184 196 uint64 cycles;
nengel@184 197 uint64 instrs;
nengel@184 198 saveCyclesAndInstrs(thisCoresIdx,cycles,instrs);
nengel@185 199 (*counterHandler)(MasterLoop_beforeAssign,schedVirtPr,tmp_cycles,tmp_instrs);
nengel@185 200 (*counterHandler)(MasterLoop_afterAssign,schedVirtPr,cycles,instrs);
engelhardt@108 201 #endif
msach@94 202 }
msach@94 203 }
nengel@177 204
msach@94 205 }
msach@94 206
msach@94 207
msach@94 208 #ifdef USE_WORK_STEALING
msach@94 209 //If no slots filled, means no more work, look for work to steal.
msach@94 210 if( numSlotsFilled == 0 )
msach@94 211 { gateProtected_stealWorkInto( currSlot, readyToAnimateQ, masterPr );
msach@94 212 }
msach@94 213 #endif
msach@94 214
msach@94 215
msach@94 216 #ifdef MEAS__TIME_MASTER
msach@94 217 saveLowTimeStampCountInto( masterPr->endMasterTSCLow );
msach@94 218 #endif
msach@94 219
msach@94 220 masterSwitchToCoreLoop(animatingPr);
msach@94 221 flushRegisters();
msach@94 222 }//MasterLoop
msach@94 223
msach@94 224
msach@94 225 }
msach@94 226
msach@94 227
msach@94 228
msach@94 229 /*This has a race condition -- the coreloops are accessing their own queues
msach@94 230 * at the same time that this work-stealer on a different core is trying to
msach@94 231 */
msach@94 232 void inline
msach@94 233 stealWorkInto( SchedSlot *currSlot, VMSQueueStruc *readyToAnimateQ,
msach@94 234 VirtProcr *masterPr )
msach@94 235 {
msach@94 236 VirtProcr *stolenPr;
msach@94 237 int32 coreIdx, i;
msach@94 238 VMSQueueStruc *currQ;
msach@94 239
msach@94 240 stolenPr = NULL;
msach@94 241 coreIdx = masterPr->coreAnimatedBy;
msach@94 242 for( i = 0; i < NUM_CORES -1; i++ )
msach@94 243 {
msach@94 244 if( coreIdx >= NUM_CORES -1 )
msach@94 245 { coreIdx = 0;
msach@94 246 }
msach@94 247 else
msach@94 248 { coreIdx++;
msach@94 249 }
msach@94 250 currQ = _VMSMasterEnv->readyToAnimateQs[coreIdx];
msach@94 251 if( numInVMSQ( currQ ) > 0 )
msach@94 252 { stolenPr = readVMSQ (currQ );
msach@94 253 break;
msach@94 254 }
msach@94 255 }
msach@94 256
msach@94 257 if( stolenPr != NULL )
msach@94 258 { currSlot->procrAssignedToSlot = stolenPr;
msach@94 259 stolenPr->schedSlot = currSlot;
msach@94 260 currSlot->needsProcrAssigned = FALSE;
msach@94 261
msach@94 262 writeVMSQ( stolenPr, readyToAnimateQ );
msach@94 263 }
msach@94 264 }
msach@94 265
msach@94 266 /*This algorithm makes the common case fast. Make the coreloop passive,
msach@94 267 * and show its progress. Make the stealer control a gate that coreloop
msach@94 268 * has to pass.
msach@94 269 *To avoid interference, only one stealer at a time. Use a global
msach@94 270 * stealer-lock.
msach@94 271 *
msach@94 272 *The pattern is based on a gate -- stealer shuts the gate, then monitors
msach@94 273 * to be sure any already past make it all the way out, before starting.
msach@94 274 *So, have a "progress" measure just before the gate, then have two after it,
msach@94 275 * one is in a "waiting room" outside the gate, the other is at the exit.
msach@94 276 *Then, the stealer first shuts the gate, then checks the progress measure
msach@94 277 * outside it, then looks to see if the progress measure at the exit is the
msach@94 278 * same. If yes, it knows the protected area is empty 'cause no other way
msach@94 279 * to get in and the last to get in also exited.
msach@94 280 *If the progress measure at the exit is not the same, then the stealer goes
msach@94 281 * into a loop checking both the waiting-area and the exit progress-measures
msach@94 282 * until one of them shows the same as the measure outside the gate. Might
msach@94 283 * as well re-read the measure outside the gate each go around, just to be
msach@94 284 * sure. It is guaranteed that one of the two will eventually match the one
msach@94 285 * outside the gate.
msach@94 286 *
msach@94 287 *Here's an informal proof of correctness:
msach@94 288 *The gate can be closed at any point, and have only four cases:
msach@94 289 * 1) coreloop made it past the gate-closing but not yet past the exit
msach@94 290 * 2) coreloop made it past the pre-gate progress update but not yet past
msach@94 291 * the gate,
msach@94 292 * 3) coreloop is right before the pre-gate update
msach@94 293 * 4) coreloop is past the exit and far from the pre-gate update.
msach@94 294 *
msach@94 295 * Covering the cases in reverse order,
msach@94 296 * 4) is not a problem -- stealer will read pre-gate progress, see that it
msach@94 297 * matches exit progress, and the gate is closed, so stealer can proceed.
msach@94 298 * 3) stealer will read pre-gate progress just after coreloop updates it..
msach@94 299 * so stealer goes into a loop until the coreloop causes wait-progress
msach@94 300 * to match pre-gate progress, so then stealer can proceed
msach@94 301 * 2) same as 3..
msach@94 302 * 1) stealer reads pre-gate progress, sees that it's different than exit,
msach@94 303 * so goes into loop until exit matches pre-gate, now it knows coreloop
msach@94 304 * is not in protected and cannot get back in, so can proceed.
msach@94 305 *
msach@94 306 *Implementation for the stealer:
msach@94 307 *
msach@94 308 *First, acquire the stealer lock -- only cores with no work to do will
msach@94 309 * compete to steal, so not a big performance penalty having only one --
msach@94 310 * will rarely have multiple stealers in a system with plenty of work -- and
msach@94 311 * in a system with little work, it doesn't matter.
msach@94 312 *
msach@94 313 *Note, have single-reader, single-writer pattern for all variables used to
msach@94 314 * communicate between stealer and victims
msach@94 315 *
msach@94 316 *So, scan the queues of the core loops, until find non-empty. Each core
msach@94 317 * has its own list that it scans. The list goes in order from closest to
msach@94 318 * furthest core, so it steals first from close cores. Later can add
msach@94 319 * taking info from the app about overlapping footprints, and scan all the
msach@94 320 * others then choose work with the most footprint overlap with the contents
msach@94 321 * of this core's cache.
msach@94 322 *
msach@94 323 *Now, have a victim want to take work from. So, shut the gate in that
msach@94 324 * coreloop, by setting the "gate closed" var on its stack to TRUE.
msach@94 325 *Then, read the core's pre-gate progress and compare to the core's exit
msach@94 326 * progress.
msach@94 327 *If same, can proceed to take work from the coreloop's queue. When done,
msach@94 328 * write FALSE to gate closed var.
msach@94 329 *If different, then enter a loop that reads the pre-gate progress, then
msach@94 330 * compares to exit progress then to wait progress. When one of two
msach@94 331 * matches, proceed. Take work from the coreloop's queue. When done,
msach@94 332 * write FALSE to the gate closed var.
msach@94 333 *
msach@94 334 */
msach@94 335 void inline
msach@94 336 gateProtected_stealWorkInto( SchedSlot *currSlot,
msach@94 337 VMSQueueStruc *myReadyToAnimateQ,
msach@94 338 VirtProcr *masterPr )
msach@94 339 {
msach@94 340 VirtProcr *stolenPr;
msach@94 341 int32 coreIdx, i, haveAVictim, gotLock;
msach@94 342 VMSQueueStruc *victimsQ;
msach@94 343
msach@94 344 volatile GateStruc *vicGate;
msach@94 345 int32 coreMightBeInProtected;
msach@94 346
msach@94 347
msach@94 348
msach@94 349 //see if any other cores have work available to steal
msach@94 350 haveAVictim = FALSE;
msach@94 351 coreIdx = masterPr->coreAnimatedBy;
msach@94 352 for( i = 0; i < NUM_CORES -1; i++ )
msach@94 353 {
msach@94 354 if( coreIdx >= NUM_CORES -1 )
msach@94 355 { coreIdx = 0;
msach@94 356 }
msach@94 357 else
msach@94 358 { coreIdx++;
msach@94 359 }
msach@94 360 victimsQ = _VMSMasterEnv->readyToAnimateQs[coreIdx];
msach@94 361 if( numInVMSQ( victimsQ ) > 0 )
msach@94 362 { haveAVictim = TRUE;
msach@94 363 vicGate = _VMSMasterEnv->workStealingGates[ coreIdx ];
msach@94 364 break;
msach@94 365 }
msach@94 366 }
msach@94 367 if( !haveAVictim ) return; //no work to steal, exit
msach@94 368
msach@94 369 //have a victim core, now get the stealer-lock
msach@94 370 gotLock =__sync_bool_compare_and_swap( &(_VMSMasterEnv->workStealingLock),
msach@94 371 UNLOCKED, LOCKED );
msach@94 372 if( !gotLock ) return; //go back to core loop, which will re-start master
msach@94 373
msach@94 374
msach@94 375 //====== Start Gate-protection =======
msach@94 376 vicGate->gateClosed = TRUE;
msach@94 377 coreMightBeInProtected= vicGate->preGateProgress != vicGate->exitProgress;
msach@94 378 while( coreMightBeInProtected )
msach@94 379 { //wait until sure
msach@94 380 if( vicGate->preGateProgress == vicGate->waitProgress )
msach@94 381 coreMightBeInProtected = FALSE;
msach@94 382 if( vicGate->preGateProgress == vicGate->exitProgress )
msach@94 383 coreMightBeInProtected = FALSE;
msach@94 384 }
msach@94 385
msach@94 386 stolenPr = readVMSQ ( victimsQ );
msach@94 387
msach@94 388 vicGate->gateClosed = FALSE;
msach@94 389 //======= End Gate-protection =======
msach@94 390
msach@94 391
msach@94 392 if( stolenPr != NULL ) //victim could have been in protected and taken
msach@94 393 { currSlot->procrAssignedToSlot = stolenPr;
msach@94 394 stolenPr->schedSlot = currSlot;
msach@94 395 currSlot->needsProcrAssigned = FALSE;
msach@94 396
msach@94 397 writeVMSQ( stolenPr, myReadyToAnimateQ );
msach@94 398 }
msach@94 399
msach@94 400 //unlock the work stealing lock
msach@94 401 _VMSMasterEnv->workStealingLock = UNLOCKED;
msach@94 402 }