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view MasterLoop.c @ 168:d7c0c0a8187a
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| author | Merten Sach <msach@mailbox.tu-berlin.de> |
|---|---|
| date | Wed, 02 Nov 2011 14:59:29 +0100 |
| parents | 5475f90c248a |
| children | aefd87f9d12f |
line source
1 /*
2 * Copyright 2010 OpenSourceStewardshipFoundation
3 *
4 * Licensed under BSD
5 */
9 #include <stdio.h>
10 #include <stddef.h>
12 #include "VMS.h"
13 #include "ProcrContext.h"
16 //===========================================================================
17 void inline
18 stealWorkInto( SchedSlot *currSlot, VMSQueueStruc *readyToAnimateQ,
19 VirtProcr *masterPr );
21 //===========================================================================
25 /*This code is animated by the virtual Master processor.
26 *
27 *Polls each sched slot exactly once, hands any requests made by a newly
28 * done slave to the "request handler" plug-in function
29 *
30 *Any slots that need a virt procr assigned are given to the "schedule"
31 * plug-in function, which tries to assign a virt procr (slave) to it.
32 *
33 *When all slots needing a processor have been given to the schedule plug-in,
34 * a fraction of the procrs successfully scheduled are put into the
35 * work queue, then a continuation of this function is put in, then the rest
36 * of the virt procrs that were successfully scheduled.
37 *
38 *The first thing the continuation does is busy-wait until the previous
39 * animation completes. This is because an (unlikely) continuation may
40 * sneak through queue before previous continuation is done putting second
41 * part of scheduled slaves in, which is the only race condition.
42 *
43 */
45 /*May 29, 2010 -- birth a Master during init so that first core loop to
46 * start running gets it and does all the stuff for a newly born --
47 * from then on, will be doing continuation, but do suspension self
48 * directly at end of master loop
49 *So VMS__init just births the master virtual processor same way it births
50 * all the others -- then does any extra setup needed and puts it into the
51 * work queue.
52 *However means have to make masterEnv a global static volatile the same way
53 * did with readyToAnimateQ in core loop. -- for performance, put the
54 * jump to the core loop directly in here, and have it directly jump back.
55 *
56 *
57 *Aug 18, 2010 -- Going to a separate MasterVP for each core, to see if this
58 * avoids the suspected bug in the system stack that causes bizarre faults
59 * at random places in the system code.
60 *
61 *So, this function is coupled to each of the MasterVPs, -- meaning this
62 * function can't rely on a particular stack and frame -- each MasterVP that
63 * animates this function has a different one.
64 *
65 *At this point, the masterLoop does not write itself into the queue anymore,
66 * instead, the coreLoop acquires the masterLock when it has nothing to
67 * animate, and then animates its own masterLoop. However, still try to put
68 * several AppVPs into the queue to amortize the startup cost of switching
69 * to the MasterVP. Note, don't have to worry about latency of requests much
70 * because most requests generate work for same core -- only latency issue
71 * is case when other cores starved and one core's requests generate work
72 * for them -- so keep max in queue to 3 or 4..
73 */
74 void masterLoop( void *initData, VirtProcr *animatingPr )
75 {
76 int32 slotIdx, numSlotsFilled;
77 VirtProcr *schedVirtPr;
78 SchedSlot *currSlot, **schedSlots;
79 MasterEnv *masterEnv;
80 VMSQueueStruc *readyToAnimateQ;
82 SlaveScheduler slaveScheduler;
83 RequestHandler requestHandler;
84 void *semanticEnv;
86 int32 thisCoresIdx;
87 VirtProcr *masterPr;
88 volatile VirtProcr *volatileMasterPr;
90 volatileMasterPr = animatingPr;
91 masterPr = (VirtProcr*)volatileMasterPr; //used to force re-define after jmp
93 //First animation of each MasterVP will in turn animate this part
94 // of setup code.. (VP creator sets up the stack as if this function
95 // was called normally, but actually get here by jmp)
96 //So, setup values about stack ptr, jmp pt and all that
97 //masterPr->nextInstrPt = &&masterLoopStartPt;
100 //Note, got rid of writing the stack and frame ptr up here, because
101 // only one
102 // core can ever animate a given MasterVP, so don't need to communicate
103 // new frame and stack ptr to the MasterVP storage before a second
104 // version of that MasterVP can get animated on a different core.
105 //Also got rid of the busy-wait.
108 //masterLoopStartPt:
109 while(1){
111 //============================= MEASUREMENT STUFF ========================
112 #ifdef MEAS__TIME_MASTER
113 //Total Master time includes one coreloop time -- just assume the core
114 // loop time is same for Master as for AppVPs, even though it may be
115 // smaller due to higher predictability of the fixed jmp.
116 saveLowTimeStampCountInto( masterPr->startMasterTSCLow );
117 #endif
118 //========================================================================
120 masterEnv = (MasterEnv*)_VMSMasterEnv;
122 //GCC may optimize so doesn't always re-define from frame-storage
123 masterPr = (VirtProcr*)volatileMasterPr; //just to make sure after jmp
124 thisCoresIdx = masterPr->coreAnimatedBy;
125 readyToAnimateQ = masterEnv->readyToAnimateQs[thisCoresIdx];
126 schedSlots = masterEnv->allSchedSlots[thisCoresIdx];
128 requestHandler = masterEnv->requestHandler;
129 slaveScheduler = masterEnv->slaveScheduler;
130 semanticEnv = masterEnv->semanticEnv;
133 //Poll each slot's Done flag
134 numSlotsFilled = 0;
135 for( slotIdx = 0; slotIdx < NUM_SCHED_SLOTS; slotIdx++)
136 {
137 currSlot = schedSlots[ slotIdx ];
139 if( currSlot->workIsDone )
140 {
141 currSlot->workIsDone = FALSE;
142 currSlot->needsProcrAssigned = TRUE;
144 //process requests from slave to master
145 //====================== MEASUREMENT STUFF ===================
146 #ifdef MEAS__TIME_PLUGIN
147 int32 startStamp1, endStamp1;
148 saveLowTimeStampCountInto( startStamp1 );
149 #endif
150 #ifdef MEAS__PERF_COUNTERS
151 int lastRecordIdx = currSlot->procrAssignedToSlot->counter_history_array_info->numInArray -1;
152 CounterRecord* lastRecord = currSlot->procrAssignedToSlot->counter_history[lastRecordIdx];
153 lastRecord->req_core = thisCoresIdx;
154 saveCyclesAndInstrs(thisCoresIdx,lastRecord->next_task_req_cycles,lastRecord->next_task_req_instrs);
155 //End of task, start of next task
156 //print counters from last run
157 addToDynArray((void*)lastRecord,masterEnv->counter_history_array_info);
158 print_record_csv_to_file(lastRecord,_VMSMasterEnv->counteroutput);
160 Dependency* newd = new_dependency(currSlot->procrAssignedToSlot->procrID,lastRecord->task_position,currSlot->procrAssignedToSlot->procrID,lastRecord->task_position + 1);
161 addToDynArray((void*) newd ,masterEnv->dependenciesInfo);
163 //print_record_human_readable(lastRecord);
164 //create new entry in record array
165 CounterRecord* newRecord = VMS__malloc(sizeof(CounterRecord));
166 newRecord->req_core = thisCoresIdx;
167 newRecord->vp_id = currSlot->procrAssignedToSlot->procrID;
168 newRecord->task_position = lastRecord->task_position + 1;
169 newRecord->req_cycles = lastRecord->next_task_req_cycles;
170 newRecord->req_instrs = lastRecord->next_task_req_instrs;
171 getReturnAddressBeforeLibraryCall(currSlot->procrAssignedToSlot, &(newRecord->addr_of_libcall_for_req));
172 addToDynArray( (void*) newRecord, currSlot->procrAssignedToSlot->counter_history_array_info);
173 lastRecord = newRecord;
174 #endif
175 //============================================================
176 (*requestHandler)( currSlot->procrAssignedToSlot, semanticEnv );
177 //====================== MEASUREMENT STUFF ===================
178 #ifdef MEAS__TIME_PLUGIN
179 saveLowTimeStampCountInto( endStamp1 );
180 addIntervalToHist( startStamp1, endStamp1,
181 _VMSMasterEnv->reqHdlrLowTimeHist );
182 addIntervalToHist( startStamp1, endStamp1,
183 _VMSMasterEnv->reqHdlrHighTimeHist );
184 #endif
185 #ifdef MEAS__PERF_COUNTERS
186 //done with constraints check
187 saveCyclesAndInstrs(thisCoresIdx,lastRecord->sc_done_cycles,lastRecord->sc_done_instrs);
188 saveLowTimeStampCountInto(lastRecord->blocked_timestamp);
189 #endif
190 //============================================================
191 }
192 if( currSlot->needsProcrAssigned )
193 { //give slot a new virt procr
194 #ifdef MEAS__PERF_COUNTERS
195 //start assigner
196 uint64 tmp_cycles;
197 uint64 tmp_instrs;
198 saveCyclesAndInstrs(thisCoresIdx,tmp_cycles,tmp_instrs);
199 #endif
200 schedVirtPr =
201 (*slaveScheduler)( semanticEnv, thisCoresIdx );
203 if( schedVirtPr != NULL )
204 { currSlot->procrAssignedToSlot = schedVirtPr;
205 schedVirtPr->schedSlot = currSlot;
206 currSlot->needsProcrAssigned = FALSE;
207 numSlotsFilled += 1;
208 #ifdef MEAS__PERF_COUNTERS
209 //end assigner
210 int lastRecordIdx = currSlot->procrAssignedToSlot->counter_history_array_info->numInArray -1;
211 CounterRecord* lastRecord = currSlot->procrAssignedToSlot->counter_history[lastRecordIdx];
212 lastRecord->assigning_core = thisCoresIdx;
213 lastRecord->start_assign_cycles = tmp_cycles;
214 lastRecord->start_assign_instrs = tmp_instrs;
215 saveCyclesAndInstrs(thisCoresIdx,lastRecord->end_assign_cycles,lastRecord->end_assign_instrs);
216 #endif
217 writeVMSQ( schedVirtPr, readyToAnimateQ );
218 }
219 }
220 }
223 #ifdef USE_WORK_STEALING
224 //If no slots filled, means no more work, look for work to steal.
225 if( numSlotsFilled == 0 )
226 { gateProtected_stealWorkInto( currSlot, readyToAnimateQ, masterPr );
227 }
228 #endif
231 #ifdef MEAS__TIME_MASTER
232 saveLowTimeStampCountInto( masterPr->endMasterTSCLow );
233 #endif
235 masterSwitchToCoreLoop(animatingPr);
236 flushRegisters();
237 }//MasterLoop
240 }
244 /*This has a race condition -- the coreloops are accessing their own queues
245 * at the same time that this work-stealer on a different core is trying to
246 */
247 void inline
248 stealWorkInto( SchedSlot *currSlot, VMSQueueStruc *readyToAnimateQ,
249 VirtProcr *masterPr )
250 {
251 VirtProcr *stolenPr;
252 int32 coreIdx, i;
253 VMSQueueStruc *currQ;
255 stolenPr = NULL;
256 coreIdx = masterPr->coreAnimatedBy;
257 for( i = 0; i < NUM_CORES -1; i++ )
258 {
259 if( coreIdx >= NUM_CORES -1 )
260 { coreIdx = 0;
261 }
262 else
263 { coreIdx++;
264 }
265 currQ = _VMSMasterEnv->readyToAnimateQs[coreIdx];
266 if( numInVMSQ( currQ ) > 0 )
267 { stolenPr = readVMSQ (currQ );
268 break;
269 }
270 }
272 if( stolenPr != NULL )
273 { currSlot->procrAssignedToSlot = stolenPr;
274 stolenPr->schedSlot = currSlot;
275 currSlot->needsProcrAssigned = FALSE;
277 writeVMSQ( stolenPr, readyToAnimateQ );
278 }
279 }
281 /*This algorithm makes the common case fast. Make the coreloop passive,
282 * and show its progress. Make the stealer control a gate that coreloop
283 * has to pass.
284 *To avoid interference, only one stealer at a time. Use a global
285 * stealer-lock.
286 *
287 *The pattern is based on a gate -- stealer shuts the gate, then monitors
288 * to be sure any already past make it all the way out, before starting.
289 *So, have a "progress" measure just before the gate, then have two after it,
290 * one is in a "waiting room" outside the gate, the other is at the exit.
291 *Then, the stealer first shuts the gate, then checks the progress measure
292 * outside it, then looks to see if the progress measure at the exit is the
293 * same. If yes, it knows the protected area is empty 'cause no other way
294 * to get in and the last to get in also exited.
295 *If the progress measure at the exit is not the same, then the stealer goes
296 * into a loop checking both the waiting-area and the exit progress-measures
297 * until one of them shows the same as the measure outside the gate. Might
298 * as well re-read the measure outside the gate each go around, just to be
299 * sure. It is guaranteed that one of the two will eventually match the one
300 * outside the gate.
301 *
302 *Here's an informal proof of correctness:
303 *The gate can be closed at any point, and have only four cases:
304 * 1) coreloop made it past the gate-closing but not yet past the exit
305 * 2) coreloop made it past the pre-gate progress update but not yet past
306 * the gate,
307 * 3) coreloop is right before the pre-gate update
308 * 4) coreloop is past the exit and far from the pre-gate update.
309 *
310 * Covering the cases in reverse order,
311 * 4) is not a problem -- stealer will read pre-gate progress, see that it
312 * matches exit progress, and the gate is closed, so stealer can proceed.
313 * 3) stealer will read pre-gate progress just after coreloop updates it..
314 * so stealer goes into a loop until the coreloop causes wait-progress
315 * to match pre-gate progress, so then stealer can proceed
316 * 2) same as 3..
317 * 1) stealer reads pre-gate progress, sees that it's different than exit,
318 * so goes into loop until exit matches pre-gate, now it knows coreloop
319 * is not in protected and cannot get back in, so can proceed.
320 *
321 *Implementation for the stealer:
322 *
323 *First, acquire the stealer lock -- only cores with no work to do will
324 * compete to steal, so not a big performance penalty having only one --
325 * will rarely have multiple stealers in a system with plenty of work -- and
326 * in a system with little work, it doesn't matter.
327 *
328 *Note, have single-reader, single-writer pattern for all variables used to
329 * communicate between stealer and victims
330 *
331 *So, scan the queues of the core loops, until find non-empty. Each core
332 * has its own list that it scans. The list goes in order from closest to
333 * furthest core, so it steals first from close cores. Later can add
334 * taking info from the app about overlapping footprints, and scan all the
335 * others then choose work with the most footprint overlap with the contents
336 * of this core's cache.
337 *
338 *Now, have a victim want to take work from. So, shut the gate in that
339 * coreloop, by setting the "gate closed" var on its stack to TRUE.
340 *Then, read the core's pre-gate progress and compare to the core's exit
341 * progress.
342 *If same, can proceed to take work from the coreloop's queue. When done,
343 * write FALSE to gate closed var.
344 *If different, then enter a loop that reads the pre-gate progress, then
345 * compares to exit progress then to wait progress. When one of two
346 * matches, proceed. Take work from the coreloop's queue. When done,
347 * write FALSE to the gate closed var.
348 *
349 */
350 void inline
351 gateProtected_stealWorkInto( SchedSlot *currSlot,
352 VMSQueueStruc *myReadyToAnimateQ,
353 VirtProcr *masterPr )
354 {
355 VirtProcr *stolenPr;
356 int32 coreIdx, i, haveAVictim, gotLock;
357 VMSQueueStruc *victimsQ;
359 volatile GateStruc *vicGate;
360 int32 coreMightBeInProtected;
364 //see if any other cores have work available to steal
365 haveAVictim = FALSE;
366 coreIdx = masterPr->coreAnimatedBy;
367 for( i = 0; i < NUM_CORES -1; i++ )
368 {
369 if( coreIdx >= NUM_CORES -1 )
370 { coreIdx = 0;
371 }
372 else
373 { coreIdx++;
374 }
375 victimsQ = _VMSMasterEnv->readyToAnimateQs[coreIdx];
376 if( numInVMSQ( victimsQ ) > 0 )
377 { haveAVictim = TRUE;
378 vicGate = _VMSMasterEnv->workStealingGates[ coreIdx ];
379 break;
380 }
381 }
382 if( !haveAVictim ) return; //no work to steal, exit
384 //have a victim core, now get the stealer-lock
385 gotLock =__sync_bool_compare_and_swap( &(_VMSMasterEnv->workStealingLock),
386 UNLOCKED, LOCKED );
387 if( !gotLock ) return; //go back to core loop, which will re-start master
390 //====== Start Gate-protection =======
391 vicGate->gateClosed = TRUE;
392 coreMightBeInProtected= vicGate->preGateProgress != vicGate->exitProgress;
393 while( coreMightBeInProtected )
394 { //wait until sure
395 if( vicGate->preGateProgress == vicGate->waitProgress )
396 coreMightBeInProtected = FALSE;
397 if( vicGate->preGateProgress == vicGate->exitProgress )
398 coreMightBeInProtected = FALSE;
399 }
401 stolenPr = readVMSQ ( victimsQ );
403 vicGate->gateClosed = FALSE;
404 //======= End Gate-protection =======
407 if( stolenPr != NULL ) //victim could have been in protected and taken
408 { currSlot->procrAssignedToSlot = stolenPr;
409 stolenPr->schedSlot = currSlot;
410 currSlot->needsProcrAssigned = FALSE;
412 writeVMSQ( stolenPr, myReadyToAnimateQ );
413 }
415 //unlock the work stealing lock
416 _VMSMasterEnv->workStealingLock = UNLOCKED;
417 }