source: libcfa/src/concurrency/ready_queue.cfa@ 5339a87

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 5339a87 was e67a82d, checked in by Peter A. Buhr <pabuhr@…>, 5 years ago

fix conflicts
  • 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
217//-----------------------------------------------------------------------
218__attribute__((hot)) bool push(struct cluster * cltr, struct $thread * thrd) with (cltr->ready_queue) {
219 __cfadbg_print_safe(ready_queue, "Kernel : Pushing %p on cluster %p\n", thrd, cltr);
220
221 // write timestamp
222 thrd->link.ts = rdtscl();
223
224 #if defined(BIAS) && !defined(__CFA_NO_STATISTICS__)
225 bool local = false;
226 int preferred =
227 //*
228 kernelTLS.this_processor ? kernelTLS.this_processor->id * 4 : -1;
229 /*/
230 thrd->link.preferred * 4;
231 //*/
232
233
234 #endif
235
236 // Try to pick a lane and lock it
237 unsigned i;
238 do {
239 // Pick the index of a lane
240 #if defined(BIAS)
241 unsigned r = __tls_rand();
242 unsigned rlow = r % BIAS;
243 unsigned rhigh = r / BIAS;
244 if((0 != rlow) && preferred >= 0) {
245 // (BIAS - 1) out of BIAS chances
246 // Use perferred queues
247 i = preferred + (rhigh % 4);
248
249 #if !defined(__CFA_NO_STATISTICS__)
250 local = true;
251 __tls_stats()->ready.pick.push.local++;
252 #endif
253 }
254 else {
255 // 1 out of BIAS chances
256 // Use all queues
257 i = rhigh;
258 local = false;
259 }
260 #else
261 i = __tls_rand();
262 #endif
263
264 i %= __atomic_load_n( &lanes.count, __ATOMIC_RELAXED );
265
266 #if !defined(__CFA_NO_STATISTICS__)
267 __tls_stats()->ready.pick.push.attempt++;
268 #endif
269
270 // If we can't lock it retry
271 } while( !__atomic_try_acquire( &lanes.data[i].lock ) );
272
273 bool first = false;
274
275 // Actually push it
276 bool lane_first = push(lanes.data[i], thrd);
277
278 #ifdef USE_SNZI
279 // If this lane used to be empty we need to do more
280 if(lane_first) {
281 // Check if the entire queue used to be empty
282 first = !query(snzi);
283
284 // Update the snzi
285 arrive( snzi, i );
286 }
287 #endif
288
289 // Unlock and return
290 __atomic_unlock( &lanes.data[i].lock );
291
292 __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);
293
294 // Update statistics
295 #if !defined(__CFA_NO_STATISTICS__)
296 #if defined(BIAS)
297 if( local ) __tls_stats()->ready.pick.push.lsuccess++;
298 #endif
299 __tls_stats()->ready.pick.push.success++;
300 #endif
301
302 // return whether or not the list was empty before this push
303 return first;
304}
305
306static struct $thread * try_pop(struct cluster * cltr, unsigned i, unsigned j);
307static struct $thread * try_pop(struct cluster * cltr, unsigned i);
308
309// Pop from the ready queue from a given cluster
310__attribute__((hot)) $thread * pop(struct cluster * cltr) with (cltr->ready_queue) {
311 /* paranoid */ verify( lanes.count > 0 );
312 unsigned count = __atomic_load_n( &lanes.count, __ATOMIC_RELAXED );
313 #if defined(BIAS)
314 // Don't bother trying locally too much
315 int local_tries = 8;
316 #endif
317
318 // As long as the list is not empty, try finding a lane that isn't empty and pop from it
319 #ifdef USE_SNZI
320 while( query(snzi) ) {
321 #else
322 for(25) {
323 #endif
324 // Pick two lists at random
325 unsigned i,j;
326 #if defined(BIAS)
327 #if !defined(__CFA_NO_STATISTICS__)
328 bool local = false;
329 #endif
330 uint64_t r = __tls_rand();
331 unsigned rlow = r % BIAS;
332 uint64_t rhigh = r / BIAS;
333 if(local_tries && 0 != rlow) {
334 // (BIAS - 1) out of BIAS chances
335 // Use perferred queues
336 unsigned pid = kernelTLS.this_processor->id * 4;
337 i = pid + (rhigh % 4);
338 j = pid + ((rhigh >> 32ull) % 4);
339
340 // count the tries
341 local_tries--;
342
343 #if !defined(__CFA_NO_STATISTICS__)
344 local = true;
345 __tls_stats()->ready.pick.pop.local++;
346 #endif
347 }
348 else {
349 // 1 out of BIAS chances
350 // Use all queues
351 i = rhigh;
352 j = rhigh >> 32ull;
353 }
354 #else
355 i = __tls_rand();
356 j = __tls_rand();
357 #endif
358
359 i %= count;
360 j %= count;
361
362 // try popping from the 2 picked lists
363 struct $thread * thrd = try_pop(cltr, i, j);
364 if(thrd) {
365 #if defined(BIAS) && !defined(__CFA_NO_STATISTICS__)
366 if( local ) __tls_stats()->ready.pick.pop.lsuccess++;
367 #endif
368 return thrd;
369 }
370 }
371
372 // All lanes where empty return 0p
373 return 0p;
374}
375
376__attribute__((hot)) struct $thread * pop_slow(struct cluster * cltr) with (cltr->ready_queue) {
377 /* paranoid */ verify( lanes.count > 0 );
378 unsigned count = __atomic_load_n( &lanes.count, __ATOMIC_RELAXED );
379 unsigned offset = __tls_rand();
380 for(i; count) {
381 unsigned idx = (offset + i) % count;
382 struct $thread * thrd = try_pop(cltr, idx);
383 if(thrd) {
384 return thrd;
385 }
386 }
387
388 // All lanes where empty return 0p
389 return 0p;
390}
391
392
393//-----------------------------------------------------------------------
394// Given 2 indexes, pick the list with the oldest push an try to pop from it
395static inline struct $thread * try_pop(struct cluster * cltr, unsigned i, unsigned j) with (cltr->ready_queue) {
396 #if !defined(__CFA_NO_STATISTICS__)
397 __tls_stats()->ready.pick.pop.attempt++;
398 #endif
399
400 // Pick the bet list
401 int w = i;
402 if( __builtin_expect(!is_empty(lanes.data[j]), true) ) {
403 w = (ts(lanes.data[i]) < ts(lanes.data[j])) ? i : j;
404 }
405
406 return try_pop(cltr, w);
407}
408
409static inline struct $thread * try_pop(struct cluster * cltr, unsigned w) with (cltr->ready_queue) {
410 // Get relevant elements locally
411 __intrusive_lane_t & lane = lanes.data[w];
412
413 // If list looks empty retry
414 if( is_empty(lane) ) return 0p;
415
416 // If we can't get the lock retry
417 if( !__atomic_try_acquire(&lane.lock) ) return 0p;
418
419
420 // If list is empty, unlock and retry
421 if( is_empty(lane) ) {
422 __atomic_unlock(&lane.lock);
423 return 0p;
424 }
425
426 // Actually pop the list
427 struct $thread * thrd;
428 thrd = pop(lane);
429
430 /* paranoid */ verify(thrd);
431 /* paranoid */ verify(lane.lock);
432
433 #ifdef USE_SNZI
434 // If this was the last element in the lane
435 if(emptied) {
436 depart( snzi, w );
437 }
438 #endif
439
440 // Unlock and return
441 __atomic_unlock(&lane.lock);
442
443 // Update statistics
444 #if !defined(__CFA_NO_STATISTICS__)
445 __tls_stats()->ready.pick.pop.success++;
446 #endif
447
448 // Update the thread bias
449 thrd->link.preferred = w / 4;
450
451 // return the popped thread
452 return thrd;
453}
454//-----------------------------------------------------------------------
455
456bool remove_head(struct cluster * cltr, struct $thread * thrd) with (cltr->ready_queue) {
457 for(i; lanes.count) {
458 __intrusive_lane_t & lane = lanes.data[i];
459
460 bool removed = false;
461
462 __atomic_acquire(&lane.lock);
463 if(head(lane)->link.next == thrd) {
464 $thread * pthrd;
465 pthrd = pop(lane);
466
467 /* paranoid */ verify( pthrd == thrd );
468
469 removed = true;
470 #ifdef USE_SNZI
471 if(emptied) {
472 depart( snzi, i );
473 }
474 #endif
475 }
476 __atomic_unlock(&lane.lock);
477
478 if( removed ) return true;
479 }
480 return false;
481}
482
483//-----------------------------------------------------------------------
484
485static void check( __ready_queue_t & q ) with (q) {
486 #if defined(__CFA_WITH_VERIFY__)
487 {
488 for( idx ; lanes.count ) {
489 __intrusive_lane_t & sl = lanes.data[idx];
490 assert(!lanes.data[idx].lock);
491
492 assert(head(sl)->link.prev == 0p );
493 assert(head(sl)->link.next->link.prev == head(sl) );
494 assert(tail(sl)->link.next == 0p );
495 assert(tail(sl)->link.prev->link.next == tail(sl) );
496
497 if(sl.before.link.ts == 0l) {
498 assert(tail(sl)->link.prev == head(sl));
499 assert(head(sl)->link.next == tail(sl));
500 } else {
501 assert(tail(sl)->link.prev != head(sl));
502 assert(head(sl)->link.next != tail(sl));
503 }
504 }
505 }
506 #endif
507}
508
509// Call this function of the intrusive list was moved using memcpy
510// fixes the list so that the pointers back to anchors aren't left dangling
511static inline void fix(__intrusive_lane_t & ll) {
512 // if the list is not empty then follow he pointer and fix its reverse
513 if(!is_empty(ll)) {
514 head(ll)->link.next->link.prev = head(ll);
515 tail(ll)->link.prev->link.next = tail(ll);
516 }
517 // Otherwise just reset the list
518 else {
519 verify(tail(ll)->link.next == 0p);
520 tail(ll)->link.prev = head(ll);
521 head(ll)->link.next = tail(ll);
522 verify(head(ll)->link.prev == 0p);
523 }
524}
525
526// Grow the ready queue
527void ready_queue_grow (struct cluster * cltr, int target) {
528 /* paranoid */ verify( ready_mutate_islocked() );
529 __cfadbg_print_safe(ready_queue, "Kernel : Growing ready queue\n");
530
531 // Make sure that everything is consistent
532 /* paranoid */ check( cltr->ready_queue );
533
534 // grow the ready queue
535 with( cltr->ready_queue ) {
536 #ifdef USE_SNZI
537 ^(snzi){};
538 #endif
539
540 // Find new count
541 // Make sure we always have atleast 1 list
542 size_t ncount = target >= 2 ? target * 4: 1;
543
544 // Allocate new array (uses realloc and memcpies the data)
545 lanes.data = alloc(lanes.data, ncount);
546
547 // Fix the moved data
548 for( idx; (size_t)lanes.count ) {
549 fix(lanes.data[idx]);
550 }
551
552 // Construct new data
553 for( idx; (size_t)lanes.count ~ ncount) {
554 (lanes.data[idx]){};
555 }
556
557 // Update original
558 lanes.count = ncount;
559
560 #ifdef USE_SNZI
561 // Re-create the snzi
562 snzi{ log2( lanes.count / 8 ) };
563 for( idx; (size_t)lanes.count ) {
564 if( !is_empty(lanes.data[idx]) ) {
565 arrive(snzi, idx);
566 }
567 }
568 #endif
569 }
570
571 // Make sure that everything is consistent
572 /* paranoid */ check( cltr->ready_queue );
573
574 __cfadbg_print_safe(ready_queue, "Kernel : Growing ready queue done\n");
575
576 /* paranoid */ verify( ready_mutate_islocked() );
577}
578
579// Shrink the ready queue
580void ready_queue_shrink(struct cluster * cltr, int target) {
581 /* paranoid */ verify( ready_mutate_islocked() );
582 __cfadbg_print_safe(ready_queue, "Kernel : Shrinking ready queue\n");
583
584 // Make sure that everything is consistent
585 /* paranoid */ check( cltr->ready_queue );
586
587 with( cltr->ready_queue ) {
588 #ifdef USE_SNZI
589 ^(snzi){};
590 #endif
591
592 // Remember old count
593 size_t ocount = lanes.count;
594
595 // Find new count
596 // Make sure we always have atleast 1 list
597 lanes.count = target >= 2 ? target * 4: 1;
598 /* paranoid */ verify( ocount >= lanes.count );
599 /* paranoid */ verify( lanes.count == target * 4 || target < 2 );
600
601 // for printing count the number of displaced threads
602 #if defined(__CFA_DEBUG_PRINT__) || defined(__CFA_DEBUG_PRINT_READY_QUEUE__)
603 __attribute__((unused)) size_t displaced = 0;
604 #endif
605
606 // redistribute old data
607 for( idx; (size_t)lanes.count ~ ocount) {
608 // Lock is not strictly needed but makes checking invariants much easier
609 __attribute__((unused)) bool locked = __atomic_try_acquire(&lanes.data[idx].lock);
610 verify(locked);
611
612 // As long as we can pop from this lane to push the threads somewhere else in the queue
613 while(!is_empty(lanes.data[idx])) {
614 struct $thread * thrd;
615 thrd = pop(lanes.data[idx]);
616
617 push(cltr, thrd);
618
619 // for printing count the number of displaced threads
620 #if defined(__CFA_DEBUG_PRINT__) || defined(__CFA_DEBUG_PRINT_READY_QUEUE__)
621 displaced++;
622 #endif
623 }
624
625 // Unlock the lane
626 __atomic_unlock(&lanes.data[idx].lock);
627
628 // TODO print the queue statistics here
629
630 ^(lanes.data[idx]){};
631 }
632
633 __cfadbg_print_safe(ready_queue, "Kernel : Shrinking ready queue displaced %zu threads\n", displaced);
634
635 // Allocate new array (uses realloc and memcpies the data)
636 lanes.data = alloc(lanes.data, lanes.count);
637
638 // Fix the moved data
639 for( idx; (size_t)lanes.count ) {
640 fix(lanes.data[idx]);
641 }
642
643 #ifdef USE_SNZI
644 // Re-create the snzi
645 snzi{ log2( lanes.count / 8 ) };
646 for( idx; (size_t)lanes.count ) {
647 if( !is_empty(lanes.data[idx]) ) {
648 arrive(snzi, idx);
649 }
650 }
651 #endif
652 }
653
654 // Make sure that everything is consistent
655 /* paranoid */ check( cltr->ready_queue );
656
657 __cfadbg_print_safe(ready_queue, "Kernel : Shrinking ready queue done\n");
658 /* paranoid */ verify( ready_mutate_islocked() );
659}
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