source: libcfa/src/concurrency/ready_queue.cfa@ 69c5c00

ADT arm-eh ast-experimental enum forall-pointer-decay jacob/cs343-translation new-ast-unique-expr pthread-emulation qualifiedEnum
Last change on this file since 69c5c00 was ceb7db8, checked in by m3zulfiq <m3zulfiq@…>, 5 years ago

Added alloc interface with backtick and removed polymorphic alloc interface. Also, changed ready_queue.cfa: 549, 640; setup.cfa: 386; to fit the new alloc interface.
  • Property mode set to 100644
File size: 18.0 KB
Line 
1//
2// Cforall Version 1.0.0 Copyright (C) 2019 University of Waterloo
3//
4// The contents of this file are covered under the licence agreement in the
5// file "LICENCE" distributed with Cforall.
6//
7// ready_queue.cfa --
8//
9// Author : Thierry Delisle
10// Created On : Mon Nov dd 16:29:18 2019
11// Last Modified By :
12// Last Modified On :
13// Update Count :
14//
15
16#define __cforall_thread__
17// #define __CFA_DEBUG_PRINT_READY_QUEUE__
18
19// #define USE_SNZI
20
21#include "bits/defs.hfa"
22#include "kernel_private.hfa"
23
24#define _GNU_SOURCE
25#include "stdlib.hfa"
26#include "math.hfa"
27
28#include <unistd.h>
29
30#include "snzi.hfa"
31#include "ready_subqueue.hfa"
32
33static const size_t cache_line_size = 64;
34
35// No overriden function, no environment variable, no define
36// fall back to a magic number
37#ifndef __CFA_MAX_PROCESSORS__
38 #define __CFA_MAX_PROCESSORS__ 1024
39#endif
40
41#define BIAS 16
42
43// returns the maximum number of processors the RWLock support
44__attribute__((weak)) unsigned __max_processors() {
45 const char * max_cores_s = getenv("CFA_MAX_PROCESSORS");
46 if(!max_cores_s) {
47 __cfadbg_print_nolock(ready_queue, "No CFA_MAX_PROCESSORS in ENV\n");
48 return __CFA_MAX_PROCESSORS__;
49 }
50
51 char * endptr = 0p;
52 long int max_cores_l = strtol(max_cores_s, &endptr, 10);
53 if(max_cores_l < 1 || max_cores_l > 65535) {
54 __cfadbg_print_nolock(ready_queue, "CFA_MAX_PROCESSORS out of range : %ld\n", max_cores_l);
55 return __CFA_MAX_PROCESSORS__;
56 }
57 if('\0' != *endptr) {
58 __cfadbg_print_nolock(ready_queue, "CFA_MAX_PROCESSORS not a decimal number : %s\n", max_cores_s);
59 return __CFA_MAX_PROCESSORS__;
60 }
61
62 return max_cores_l;
63}
64
65//=======================================================================
66// Cluster wide reader-writer lock
67//=======================================================================
68void ?{}(__scheduler_RWLock_t & this) {
69 this.max = __max_processors();
70 this.alloc = 0;
71 this.ready = 0;
72 this.lock = false;
73 this.data = alloc(this.max);
74
75 /*paranoid*/ verify( 0 == (((uintptr_t)(this.data )) % 64) );
76 /*paranoid*/ verify( 0 == (((uintptr_t)(this.data + 1)) % 64) );
77 /*paranoid*/ verify(__atomic_is_lock_free(sizeof(this.alloc), &this.alloc));
78 /*paranoid*/ verify(__atomic_is_lock_free(sizeof(this.ready), &this.ready));
79
80}
81void ^?{}(__scheduler_RWLock_t & this) {
82 free(this.data);
83}
84
85void ?{}( __scheduler_lock_id_t & this, __processor_id_t * proc ) {
86 this.handle = proc;
87 this.lock = false;
88 #ifdef __CFA_WITH_VERIFY__
89 this.owned = false;
90 #endif
91}
92
93//=======================================================================
94// Lock-Free registering/unregistering of threads
95unsigned doregister( struct __processor_id_t * proc ) with(*__scheduler_lock) {
96 __cfadbg_print_safe(ready_queue, "Kernel : Registering proc %p for RW-Lock\n", proc);
97
98 // Step - 1 : check if there is already space in the data
99 uint_fast32_t s = ready;
100
101 // Check among all the ready
102 for(uint_fast32_t i = 0; i < s; i++) {
103 __processor_id_t * null = 0p; // Re-write every loop since compare thrashes it
104 if( __atomic_load_n(&data[i].handle, (int)__ATOMIC_RELAXED) == null
105 && __atomic_compare_exchange_n( &data[i].handle, &null, proc, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
106 /*paranoid*/ verify(i < ready);
107 /*paranoid*/ verify(0 == (__alignof__(data[i]) % cache_line_size));
108 /*paranoid*/ verify((((uintptr_t)&data[i]) % cache_line_size) == 0);
109 return i;
110 }
111 }
112
113 if(max <= alloc) abort("Trying to create more than %ud processors", __scheduler_lock->max);
114
115 // Step - 2 : F&A to get a new spot in the array.
116 uint_fast32_t n = __atomic_fetch_add(&alloc, 1, __ATOMIC_SEQ_CST);
117 if(max <= n) abort("Trying to create more than %ud processors", __scheduler_lock->max);
118
119 // Step - 3 : Mark space as used and then publish it.
120 __scheduler_lock_id_t * storage = (__scheduler_lock_id_t *)&data[n];
121 (*storage){ proc };
122 while() {
123 unsigned copy = n;
124 if( __atomic_load_n(&ready, __ATOMIC_RELAXED) == n
125 && __atomic_compare_exchange_n(&ready, &copy, n + 1, true, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST))
126 break;
127 Pause();
128 }
129
130 __cfadbg_print_safe(ready_queue, "Kernel : Registering proc %p done, id %lu\n", proc, n);
131
132 // Return new spot.
133 /*paranoid*/ verify(n < ready);
134 /*paranoid*/ verify(__alignof__(data[n]) == (2 * cache_line_size));
135 /*paranoid*/ verify((((uintptr_t)&data[n]) % cache_line_size) == 0);
136 return n;
137}
138
139void unregister( struct __processor_id_t * proc ) with(*__scheduler_lock) {
140 unsigned id = proc->id;
141 /*paranoid*/ verify(id < ready);
142 /*paranoid*/ verify(proc == __atomic_load_n(&data[id].handle, __ATOMIC_RELAXED));
143 __atomic_store_n(&data[id].handle, 0p, __ATOMIC_RELEASE);
144
145 __cfadbg_print_safe(ready_queue, "Kernel : Unregister proc %p\n", proc);
146}
147
148//-----------------------------------------------------------------------
149// Writer side : acquire when changing the ready queue, e.g. adding more
150// queues or removing them.
151uint_fast32_t ready_mutate_lock( void ) with(*__scheduler_lock) {
152 /* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
153
154 // Step 1 : lock global lock
155 // It is needed to avoid processors that register mid Critical-Section
156 // to simply lock their own lock and enter.
157 __atomic_acquire( &lock );
158
159 // Step 2 : lock per-proc lock
160 // Processors that are currently being registered aren't counted
161 // but can't be in read_lock or in the critical section.
162 // All other processors are counted
163 uint_fast32_t s = ready;
164 for(uint_fast32_t i = 0; i < s; i++) {
165 __atomic_acquire( &data[i].lock );
166 }
167
168 /* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
169 return s;
170}
171
172void ready_mutate_unlock( uint_fast32_t last_s ) with(*__scheduler_lock) {
173 /* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
174
175 // Step 1 : release local locks
176 // This must be done while the global lock is held to avoid
177 // threads that where created mid critical section
178 // to race to lock their local locks and have the writer
179 // immidiately unlock them
180 // Alternative solution : return s in write_lock and pass it to write_unlock
181 for(uint_fast32_t i = 0; i < last_s; i++) {
182 verify(data[i].lock);
183 __atomic_store_n(&data[i].lock, (bool)false, __ATOMIC_RELEASE);
184 }
185
186 // Step 2 : release global lock
187 /*paranoid*/ assert(true == lock);
188 __atomic_store_n(&lock, (bool)false, __ATOMIC_RELEASE);
189
190 /* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
191}
192
193//=======================================================================
194// Cforall Reqdy Queue used for scheduling
195//=======================================================================
196void ?{}(__ready_queue_t & this) with (this) {
197 lanes.data = 0p;
198 lanes.count = 0;
199}
200
201void ^?{}(__ready_queue_t & this) with (this) {
202 verify( 1 == lanes.count );
203 #ifdef USE_SNZI
204 verify( !query( snzi ) );
205 #endif
206 free(lanes.data);
207}
208
209//-----------------------------------------------------------------------
210__attribute__((hot)) bool query(struct cluster * cltr) {
211 #ifdef USE_SNZI
212 return query(cltr->ready_queue.snzi);
213 #endif
214 return true;
215}
216
217static inline [unsigned, bool] idx_from_r(unsigned r, unsigned preferred) {
218 unsigned i;
219 bool local;
220 #if defined(BIAS)
221 unsigned rlow = r % BIAS;
222 unsigned rhigh = r / BIAS;
223 if((0 != rlow) && preferred >= 0) {
224 // (BIAS - 1) out of BIAS chances
225 // Use perferred queues
226 i = preferred + (rhigh % 4);
227 local = true;
228 }
229 else {
230 // 1 out of BIAS chances
231 // Use all queues
232 i = rhigh;
233 local = false;
234 }
235 #else
236 i = r;
237 local = false;
238 #endif
239 return [i, local];
240}
241
242//-----------------------------------------------------------------------
243__attribute__((hot)) bool push(struct cluster * cltr, struct $thread * thrd) with (cltr->ready_queue) {
244 __cfadbg_print_safe(ready_queue, "Kernel : Pushing %p on cluster %p\n", thrd, cltr);
245
246 // write timestamp
247 thrd->link.ts = rdtscl();
248
249 __attribute__((unused)) bool local;
250 __attribute__((unused)) int preferred;
251 #if defined(BIAS)
252 preferred =
253 //*
254 kernelTLS.this_processor ? kernelTLS.this_processor->id * 4 : -1;
255 /*/
256 thrd->link.preferred * 4;
257 //*/
258 #endif
259
260 // Try to pick a lane and lock it
261 unsigned i;
262 do {
263 // Pick the index of a lane
264 // unsigned r = __tls_rand();
265 unsigned r = __tls_rand_fwd();
266 [i, local] = idx_from_r(r, preferred);
267
268 #if !defined(__CFA_NO_STATISTICS__)
269 if(local) {
270 __tls_stats()->ready.pick.push.local++;
271 }
272 #endif
273
274 i %= __atomic_load_n( &lanes.count, __ATOMIC_RELAXED );
275
276 #if !defined(__CFA_NO_STATISTICS__)
277 __tls_stats()->ready.pick.push.attempt++;
278 #endif
279
280 // If we can't lock it retry
281 } while( !__atomic_try_acquire( &lanes.data[i].lock ) );
282
283 bool first = false;
284
285 // Actually push it
286 #ifdef USE_SNZI
287 bool lane_first =
288 #endif
289
290 push(lanes.data[i], thrd);
291
292 #ifdef USE_SNZI
293 // If this lane used to be empty we need to do more
294 if(lane_first) {
295 // Check if the entire queue used to be empty
296 first = !query(snzi);
297
298 // Update the snzi
299 arrive( snzi, i );
300 }
301 #endif
302
303 __tls_rand_advance_bck();
304
305 // Unlock and return
306 __atomic_unlock( &lanes.data[i].lock );
307
308 __cfadbg_print_safe(ready_queue, "Kernel : Pushed %p on cluster %p (idx: %u, mask %llu, first %d)\n", thrd, cltr, i, used.mask[0], lane_first);
309
310 // Update statistics
311 #if !defined(__CFA_NO_STATISTICS__)
312 #if defined(BIAS)
313 if( local ) __tls_stats()->ready.pick.push.lsuccess++;
314 #endif
315 __tls_stats()->ready.pick.push.success++;
316 #endif
317
318 // return whether or not the list was empty before this push
319 return first;
320}
321
322static struct $thread * try_pop(struct cluster * cltr, unsigned i, unsigned j);
323static struct $thread * try_pop(struct cluster * cltr, unsigned i);
324
325// Pop from the ready queue from a given cluster
326__attribute__((hot)) $thread * pop(struct cluster * cltr) with (cltr->ready_queue) {
327 /* paranoid */ verify( lanes.count > 0 );
328 unsigned count = __atomic_load_n( &lanes.count, __ATOMIC_RELAXED );
329 int preferred;
330 #if defined(BIAS)
331 // Don't bother trying locally too much
332 int local_tries = 8;
333 preferred = kernelTLS.this_processor->id * 4;
334 #endif
335
336
337 // As long as the list is not empty, try finding a lane that isn't empty and pop from it
338 #ifdef USE_SNZI
339 while( query(snzi) ) {
340 #else
341 for(25) {
342 #endif
343 // Pick two lists at random
344 // unsigned ri = __tls_rand();
345 // unsigned rj = __tls_rand();
346 unsigned ri = __tls_rand_bck();
347 unsigned rj = __tls_rand_bck();
348
349 unsigned i, j;
350 __attribute__((unused)) bool locali, localj;
351 [i, locali] = idx_from_r(ri, preferred);
352 [j, localj] = idx_from_r(rj, preferred);
353
354 #if !defined(__CFA_NO_STATISTICS__)
355 if(locali) {
356 __tls_stats()->ready.pick.pop.local++;
357 }
358 if(localj) {
359 __tls_stats()->ready.pick.pop.local++;
360 }
361 #endif
362
363 i %= count;
364 j %= count;
365
366 // try popping from the 2 picked lists
367 struct $thread * thrd = try_pop(cltr, i, j);
368 if(thrd) {
369 #if defined(BIAS) && !defined(__CFA_NO_STATISTICS__)
370 if( locali || localj ) __tls_stats()->ready.pick.pop.lsuccess++;
371 #endif
372 return thrd;
373 }
374 }
375
376 // All lanes where empty return 0p
377 return 0p;
378}
379
380__attribute__((hot)) struct $thread * pop_slow(struct cluster * cltr) with (cltr->ready_queue) {
381 /* paranoid */ verify( lanes.count > 0 );
382 unsigned count = __atomic_load_n( &lanes.count, __ATOMIC_RELAXED );
383 unsigned offset = __tls_rand();
384 for(i; count) {
385 unsigned idx = (offset + i) % count;
386 struct $thread * thrd = try_pop(cltr, idx);
387 if(thrd) {
388 return thrd;
389 }
390 }
391
392 // All lanes where empty return 0p
393 return 0p;
394}
395
396
397//-----------------------------------------------------------------------
398// Given 2 indexes, pick the list with the oldest push an try to pop from it
399static inline struct $thread * try_pop(struct cluster * cltr, unsigned i, unsigned j) with (cltr->ready_queue) {
400 #if !defined(__CFA_NO_STATISTICS__)
401 __tls_stats()->ready.pick.pop.attempt++;
402 #endif
403
404 // Pick the bet list
405 int w = i;
406 if( __builtin_expect(!is_empty(lanes.data[j]), true) ) {
407 w = (ts(lanes.data[i]) < ts(lanes.data[j])) ? i : j;
408 }
409
410 return try_pop(cltr, w);
411}
412
413static inline struct $thread * try_pop(struct cluster * cltr, unsigned w) with (cltr->ready_queue) {
414 // Get relevant elements locally
415 __intrusive_lane_t & lane = lanes.data[w];
416
417 // If list looks empty retry
418 if( is_empty(lane) ) return 0p;
419
420 // If we can't get the lock retry
421 if( !__atomic_try_acquire(&lane.lock) ) return 0p;
422
423
424 // If list is empty, unlock and retry
425 if( is_empty(lane) ) {
426 __atomic_unlock(&lane.lock);
427 return 0p;
428 }
429
430 // Actually pop the list
431 struct $thread * thrd;
432 thrd = pop(lane);
433
434 /* paranoid */ verify(thrd);
435 /* paranoid */ verify(lane.lock);
436
437 #ifdef USE_SNZI
438 // If this was the last element in the lane
439 if(emptied) {
440 depart( snzi, w );
441 }
442 #endif
443
444 // Unlock and return
445 __atomic_unlock(&lane.lock);
446
447 // Update statistics
448 #if !defined(__CFA_NO_STATISTICS__)
449 __tls_stats()->ready.pick.pop.success++;
450 #endif
451
452 // Update the thread bias
453 thrd->link.preferred = w / 4;
454
455 // return the popped thread
456 return thrd;
457}
458//-----------------------------------------------------------------------
459
460bool remove_head(struct cluster * cltr, struct $thread * thrd) with (cltr->ready_queue) {
461 for(i; lanes.count) {
462 __intrusive_lane_t & lane = lanes.data[i];
463
464 bool removed = false;
465
466 __atomic_acquire(&lane.lock);
467 if(head(lane)->link.next == thrd) {
468 $thread * pthrd;
469 pthrd = pop(lane);
470
471 /* paranoid */ verify( pthrd == thrd );
472
473 removed = true;
474 #ifdef USE_SNZI
475 if(emptied) {
476 depart( snzi, i );
477 }
478 #endif
479 }
480 __atomic_unlock(&lane.lock);
481
482 if( removed ) return true;
483 }
484 return false;
485}
486
487//-----------------------------------------------------------------------
488
489static void check( __ready_queue_t & q ) with (q) {
490 #if defined(__CFA_WITH_VERIFY__)
491 {
492 for( idx ; lanes.count ) {
493 __intrusive_lane_t & sl = lanes.data[idx];
494 assert(!lanes.data[idx].lock);
495
496 assert(head(sl)->link.prev == 0p );
497 assert(head(sl)->link.next->link.prev == head(sl) );
498 assert(tail(sl)->link.next == 0p );
499 assert(tail(sl)->link.prev->link.next == tail(sl) );
500
501 if(sl.before.link.ts == 0l) {
502 assert(tail(sl)->link.prev == head(sl));
503 assert(head(sl)->link.next == tail(sl));
504 } else {
505 assert(tail(sl)->link.prev != head(sl));
506 assert(head(sl)->link.next != tail(sl));
507 }
508 }
509 }
510 #endif
511}
512
513// Call this function of the intrusive list was moved using memcpy
514// fixes the list so that the pointers back to anchors aren't left dangling
515static inline void fix(__intrusive_lane_t & ll) {
516 // if the list is not empty then follow he pointer and fix its reverse
517 if(!is_empty(ll)) {
518 head(ll)->link.next->link.prev = head(ll);
519 tail(ll)->link.prev->link.next = tail(ll);
520 }
521 // Otherwise just reset the list
522 else {
523 verify(tail(ll)->link.next == 0p);
524 tail(ll)->link.prev = head(ll);
525 head(ll)->link.next = tail(ll);
526 verify(head(ll)->link.prev == 0p);
527 }
528}
529
530// Grow the ready queue
531void ready_queue_grow (struct cluster * cltr, int target) {
532 /* paranoid */ verify( ready_mutate_islocked() );
533 __cfadbg_print_safe(ready_queue, "Kernel : Growing ready queue\n");
534
535 // Make sure that everything is consistent
536 /* paranoid */ check( cltr->ready_queue );
537
538 // grow the ready queue
539 with( cltr->ready_queue ) {
540 #ifdef USE_SNZI
541 ^(snzi){};
542 #endif
543
544 // Find new count
545 // Make sure we always have atleast 1 list
546 size_t ncount = target >= 2 ? target * 4: 1;
547
548 // Allocate new array (uses realloc and memcpies the data)
549 lanes.data = alloc( ncount, lanes.data`realloc );
550
551 // Fix the moved data
552 for( idx; (size_t)lanes.count ) {
553 fix(lanes.data[idx]);
554 }
555
556 // Construct new data
557 for( idx; (size_t)lanes.count ~ ncount) {
558 (lanes.data[idx]){};
559 }
560
561 // Update original
562 lanes.count = ncount;
563
564 #ifdef USE_SNZI
565 // Re-create the snzi
566 snzi{ log2( lanes.count / 8 ) };
567 for( idx; (size_t)lanes.count ) {
568 if( !is_empty(lanes.data[idx]) ) {
569 arrive(snzi, idx);
570 }
571 }
572 #endif
573 }
574
575 // Make sure that everything is consistent
576 /* paranoid */ check( cltr->ready_queue );
577
578 __cfadbg_print_safe(ready_queue, "Kernel : Growing ready queue done\n");
579
580 /* paranoid */ verify( ready_mutate_islocked() );
581}
582
583// Shrink the ready queue
584void ready_queue_shrink(struct cluster * cltr, int target) {
585 /* paranoid */ verify( ready_mutate_islocked() );
586 __cfadbg_print_safe(ready_queue, "Kernel : Shrinking ready queue\n");
587
588 // Make sure that everything is consistent
589 /* paranoid */ check( cltr->ready_queue );
590
591 with( cltr->ready_queue ) {
592 #ifdef USE_SNZI
593 ^(snzi){};
594 #endif
595
596 // Remember old count
597 size_t ocount = lanes.count;
598
599 // Find new count
600 // Make sure we always have atleast 1 list
601 lanes.count = target >= 2 ? target * 4: 1;
602 /* paranoid */ verify( ocount >= lanes.count );
603 /* paranoid */ verify( lanes.count == target * 4 || target < 2 );
604
605 // for printing count the number of displaced threads
606 #if defined(__CFA_DEBUG_PRINT__) || defined(__CFA_DEBUG_PRINT_READY_QUEUE__)
607 __attribute__((unused)) size_t displaced = 0;
608 #endif
609
610 // redistribute old data
611 for( idx; (size_t)lanes.count ~ ocount) {
612 // Lock is not strictly needed but makes checking invariants much easier
613 __attribute__((unused)) bool locked = __atomic_try_acquire(&lanes.data[idx].lock);
614 verify(locked);
615
616 // As long as we can pop from this lane to push the threads somewhere else in the queue
617 while(!is_empty(lanes.data[idx])) {
618 struct $thread * thrd;
619 thrd = pop(lanes.data[idx]);
620
621 push(cltr, thrd);
622
623 // for printing count the number of displaced threads
624 #if defined(__CFA_DEBUG_PRINT__) || defined(__CFA_DEBUG_PRINT_READY_QUEUE__)
625 displaced++;
626 #endif
627 }
628
629 // Unlock the lane
630 __atomic_unlock(&lanes.data[idx].lock);
631
632 // TODO print the queue statistics here
633
634 ^(lanes.data[idx]){};
635 }
636
637 __cfadbg_print_safe(ready_queue, "Kernel : Shrinking ready queue displaced %zu threads\n", displaced);
638
639 // Allocate new array (uses realloc and memcpies the data)
640 lanes.data = alloc( lanes.count, lanes.data`realloc );
641
642 // Fix the moved data
643 for( idx; (size_t)lanes.count ) {
644 fix(lanes.data[idx]);
645 }
646
647 #ifdef USE_SNZI
648 // Re-create the snzi
649 snzi{ log2( lanes.count / 8 ) };
650 for( idx; (size_t)lanes.count ) {
651 if( !is_empty(lanes.data[idx]) ) {
652 arrive(snzi, idx);
653 }
654 }
655 #endif
656 }
657
658 // Make sure that everything is consistent
659 /* paranoid */ check( cltr->ready_queue );
660
661 __cfadbg_print_safe(ready_queue, "Kernel : Shrinking ready queue done\n");
662 /* paranoid */ verify( ready_mutate_islocked() );
663}
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