source: libcfa/src/concurrency/ready_queue.cfa@ 1d5deea

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 1d5deea was 341aa39, checked in by Thierry Delisle <tdelisle@…>, 4 years ago

Fix bugs in workstealing edge cases:

  • cutoff was wrong of all local queues are empty
  • target would get stuck if the rng returned the local queues
  • Property mode set to 100644
File size: 22.3 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_MPSC
20
21#define USE_RELAXED_FIFO
22// #define USE_WORK_STEALING
23
24#include "bits/defs.hfa"
25#include "kernel_private.hfa"
26
27#define _GNU_SOURCE
28#include "stdlib.hfa"
29#include "math.hfa"
30
31#include <unistd.h>
32
33#include "ready_subqueue.hfa"
34
35static const size_t cache_line_size = 64;
36
37#if !defined(__CFA_NO_STATISTICS__)
38 #define __STATS(...) __VA_ARGS__
39#else
40 #define __STATS(...)
41#endif
42
43// No overriden function, no environment variable, no define
44// fall back to a magic number
45#ifndef __CFA_MAX_PROCESSORS__
46 #define __CFA_MAX_PROCESSORS__ 1024
47#endif
48
49#if defined(USE_RELAXED_FIFO)
50 #define BIAS 4
51 #define READYQ_SHARD_FACTOR 4
52 #define SEQUENTIAL_SHARD 1
53#elif defined(USE_WORK_STEALING)
54 #define READYQ_SHARD_FACTOR 2
55 #define SEQUENTIAL_SHARD 2
56#else
57 #error no scheduling strategy selected
58#endif
59
60static inline struct $thread * try_pop(struct cluster * cltr, unsigned w __STATS(, __stats_readyQ_pop_t & stats));
61static inline struct $thread * try_pop(struct cluster * cltr, unsigned i, unsigned j __STATS(, __stats_readyQ_pop_t & stats));
62static inline struct $thread * search(struct cluster * cltr);
63static inline [unsigned, bool] idx_from_r(unsigned r, unsigned preferred);
64
65
66// returns the maximum number of processors the RWLock support
67__attribute__((weak)) unsigned __max_processors() {
68 const char * max_cores_s = getenv("CFA_MAX_PROCESSORS");
69 if(!max_cores_s) {
70 __cfadbg_print_nolock(ready_queue, "No CFA_MAX_PROCESSORS in ENV\n");
71 return __CFA_MAX_PROCESSORS__;
72 }
73
74 char * endptr = 0p;
75 long int max_cores_l = strtol(max_cores_s, &endptr, 10);
76 if(max_cores_l < 1 || max_cores_l > 65535) {
77 __cfadbg_print_nolock(ready_queue, "CFA_MAX_PROCESSORS out of range : %ld\n", max_cores_l);
78 return __CFA_MAX_PROCESSORS__;
79 }
80 if('\0' != *endptr) {
81 __cfadbg_print_nolock(ready_queue, "CFA_MAX_PROCESSORS not a decimal number : %s\n", max_cores_s);
82 return __CFA_MAX_PROCESSORS__;
83 }
84
85 return max_cores_l;
86}
87
88//=======================================================================
89// Cluster wide reader-writer lock
90//=======================================================================
91void ?{}(__scheduler_RWLock_t & this) {
92 this.max = __max_processors();
93 this.alloc = 0;
94 this.ready = 0;
95 this.lock = false;
96 this.data = alloc(this.max);
97
98 /*paranoid*/ verify( 0 == (((uintptr_t)(this.data )) % 64) );
99 /*paranoid*/ verify( 0 == (((uintptr_t)(this.data + 1)) % 64) );
100 /*paranoid*/ verify(__atomic_is_lock_free(sizeof(this.alloc), &this.alloc));
101 /*paranoid*/ verify(__atomic_is_lock_free(sizeof(this.ready), &this.ready));
102
103}
104void ^?{}(__scheduler_RWLock_t & this) {
105 free(this.data);
106}
107
108void ?{}( __scheduler_lock_id_t & this, __processor_id_t * proc ) {
109 this.handle = proc;
110 this.lock = false;
111 #ifdef __CFA_WITH_VERIFY__
112 this.owned = false;
113 #endif
114}
115
116//=======================================================================
117// Lock-Free registering/unregistering of threads
118void register_proc_id( struct __processor_id_t * proc ) with(*__scheduler_lock) {
119 __cfadbg_print_safe(ready_queue, "Kernel : Registering proc %p for RW-Lock\n", proc);
120
121 // Step - 1 : check if there is already space in the data
122 uint_fast32_t s = ready;
123
124 // Check among all the ready
125 for(uint_fast32_t i = 0; i < s; i++) {
126 __processor_id_t * null = 0p; // Re-write every loop since compare thrashes it
127 if( __atomic_load_n(&data[i].handle, (int)__ATOMIC_RELAXED) == null
128 && __atomic_compare_exchange_n( &data[i].handle, &null, proc, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
129 /*paranoid*/ verify(i < ready);
130 /*paranoid*/ verify(0 == (__alignof__(data[i]) % cache_line_size));
131 /*paranoid*/ verify((((uintptr_t)&data[i]) % cache_line_size) == 0);
132 proc->id = i;
133 }
134 }
135
136 if(max <= alloc) abort("Trying to create more than %ud processors", __scheduler_lock->max);
137
138 // Step - 2 : F&A to get a new spot in the array.
139 uint_fast32_t n = __atomic_fetch_add(&alloc, 1, __ATOMIC_SEQ_CST);
140 if(max <= n) abort("Trying to create more than %ud processors", __scheduler_lock->max);
141
142 // Step - 3 : Mark space as used and then publish it.
143 __scheduler_lock_id_t * storage = (__scheduler_lock_id_t *)&data[n];
144 (*storage){ proc };
145 while() {
146 unsigned copy = n;
147 if( __atomic_load_n(&ready, __ATOMIC_RELAXED) == n
148 && __atomic_compare_exchange_n(&ready, &copy, n + 1, true, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST))
149 break;
150 Pause();
151 }
152
153 __cfadbg_print_safe(ready_queue, "Kernel : Registering proc %p done, id %lu\n", proc, n);
154
155 // Return new spot.
156 /*paranoid*/ verify(n < ready);
157 /*paranoid*/ verify(__alignof__(data[n]) == (2 * cache_line_size));
158 /*paranoid*/ verify((((uintptr_t)&data[n]) % cache_line_size) == 0);
159 proc->id = n;
160}
161
162void unregister_proc_id( struct __processor_id_t * proc ) with(*__scheduler_lock) {
163 unsigned id = proc->id;
164 /*paranoid*/ verify(id < ready);
165 /*paranoid*/ verify(proc == __atomic_load_n(&data[id].handle, __ATOMIC_RELAXED));
166 __atomic_store_n(&data[id].handle, 0p, __ATOMIC_RELEASE);
167
168 __cfadbg_print_safe(ready_queue, "Kernel : Unregister proc %p\n", proc);
169}
170
171//-----------------------------------------------------------------------
172// Writer side : acquire when changing the ready queue, e.g. adding more
173// queues or removing them.
174uint_fast32_t ready_mutate_lock( void ) with(*__scheduler_lock) {
175 /* paranoid */ verify( ! __preemption_enabled() );
176
177 // Step 1 : lock global lock
178 // It is needed to avoid processors that register mid Critical-Section
179 // to simply lock their own lock and enter.
180 __atomic_acquire( &lock );
181
182 // Step 2 : lock per-proc lock
183 // Processors that are currently being registered aren't counted
184 // but can't be in read_lock or in the critical section.
185 // All other processors are counted
186 uint_fast32_t s = ready;
187 for(uint_fast32_t i = 0; i < s; i++) {
188 __atomic_acquire( &data[i].lock );
189 }
190
191 /* paranoid */ verify( ! __preemption_enabled() );
192 return s;
193}
194
195void ready_mutate_unlock( uint_fast32_t last_s ) with(*__scheduler_lock) {
196 /* paranoid */ verify( ! __preemption_enabled() );
197
198 // Step 1 : release local locks
199 // This must be done while the global lock is held to avoid
200 // threads that where created mid critical section
201 // to race to lock their local locks and have the writer
202 // immidiately unlock them
203 // Alternative solution : return s in write_lock and pass it to write_unlock
204 for(uint_fast32_t i = 0; i < last_s; i++) {
205 verify(data[i].lock);
206 __atomic_store_n(&data[i].lock, (bool)false, __ATOMIC_RELEASE);
207 }
208
209 // Step 2 : release global lock
210 /*paranoid*/ assert(true == lock);
211 __atomic_store_n(&lock, (bool)false, __ATOMIC_RELEASE);
212
213 /* paranoid */ verify( ! __preemption_enabled() );
214}
215
216//=======================================================================
217// Cforall Ready Queue used for scheduling
218//=======================================================================
219void ?{}(__ready_queue_t & this) with (this) {
220 lanes.data = 0p;
221 lanes.tscs = 0p;
222 lanes.count = 0;
223}
224
225void ^?{}(__ready_queue_t & this) with (this) {
226 verify( SEQUENTIAL_SHARD == lanes.count );
227 free(lanes.data);
228 free(lanes.tscs);
229}
230
231//-----------------------------------------------------------------------
232#if defined(USE_RELAXED_FIFO)
233 //-----------------------------------------------------------------------
234 // get index from random number with or without bias towards queues
235 static inline [unsigned, bool] idx_from_r(unsigned r, unsigned preferred) {
236 unsigned i;
237 bool local;
238 unsigned rlow = r % BIAS;
239 unsigned rhigh = r / BIAS;
240 if((0 != rlow) && preferred >= 0) {
241 // (BIAS - 1) out of BIAS chances
242 // Use perferred queues
243 i = preferred + (rhigh % READYQ_SHARD_FACTOR);
244 local = true;
245 }
246 else {
247 // 1 out of BIAS chances
248 // Use all queues
249 i = rhigh;
250 local = false;
251 }
252 return [i, local];
253 }
254
255 __attribute__((hot)) void push(struct cluster * cltr, struct $thread * thrd) with (cltr->ready_queue) {
256 __cfadbg_print_safe(ready_queue, "Kernel : Pushing %p on cluster %p\n", thrd, cltr);
257
258 const bool external = (!kernelTLS().this_processor) || (cltr != kernelTLS().this_processor->cltr);
259 /* paranoid */ verify(external || kernelTLS().this_processor->rdq.id < lanes.count );
260
261 // write timestamp
262 thrd->link.ts = rdtscl();
263
264 bool local;
265 int preferred = external ? -1 : kernelTLS().this_processor->rdq.id;
266
267 // Try to pick a lane and lock it
268 unsigned i;
269 do {
270 // Pick the index of a lane
271 unsigned r = __tls_rand_fwd();
272 [i, local] = idx_from_r(r, preferred);
273
274 i %= __atomic_load_n( &lanes.count, __ATOMIC_RELAXED );
275
276 #if !defined(__CFA_NO_STATISTICS__)
277 if(unlikely(external)) __atomic_fetch_add(&cltr->stats->ready.push.extrn.attempt, 1, __ATOMIC_RELAXED);
278 else if(local) __tls_stats()->ready.push.local.attempt++;
279 else __tls_stats()->ready.push.share.attempt++;
280 #endif
281
282 #if defined(USE_MPSC)
283 // mpsc always succeeds
284 } while( false );
285 #else
286 // If we can't lock it retry
287 } while( !__atomic_try_acquire( &lanes.data[i].lock ) );
288 #endif
289
290 // Actually push it
291 push(lanes.data[i], thrd);
292
293 #if !defined(USE_MPSC)
294 // Unlock and return
295 __atomic_unlock( &lanes.data[i].lock );
296 #endif
297
298 // Mark the current index in the tls rng instance as having an item
299 __tls_rand_advance_bck();
300
301 __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);
302
303 // Update statistics
304 #if !defined(__CFA_NO_STATISTICS__)
305 if(unlikely(external)) __atomic_fetch_add(&cltr->stats->ready.push.extrn.success, 1, __ATOMIC_RELAXED);
306 else if(local) __tls_stats()->ready.push.local.success++;
307 else __tls_stats()->ready.push.share.success++;
308 #endif
309 }
310
311 // Pop from the ready queue from a given cluster
312 __attribute__((hot)) $thread * pop_fast(struct cluster * cltr) with (cltr->ready_queue) {
313 /* paranoid */ verify( lanes.count > 0 );
314 /* paranoid */ verify( kernelTLS().this_processor );
315 /* paranoid */ verify( kernelTLS().this_processor->rdq.id < lanes.count );
316
317 unsigned count = __atomic_load_n( &lanes.count, __ATOMIC_RELAXED );
318 int preferred = kernelTLS().this_processor->rdq.id;
319
320
321 // As long as the list is not empty, try finding a lane that isn't empty and pop from it
322 for(25) {
323 // Pick two lists at random
324 unsigned ri = __tls_rand_bck();
325 unsigned rj = __tls_rand_bck();
326
327 unsigned i, j;
328 __attribute__((unused)) bool locali, localj;
329 [i, locali] = idx_from_r(ri, preferred);
330 [j, localj] = idx_from_r(rj, preferred);
331
332 i %= count;
333 j %= count;
334
335 // try popping from the 2 picked lists
336 struct $thread * thrd = try_pop(cltr, i, j __STATS(, *(locali || localj ? &__tls_stats()->ready.pop.local : &__tls_stats()->ready.pop.help)));
337 if(thrd) {
338 return thrd;
339 }
340 }
341
342 // All lanes where empty return 0p
343 return 0p;
344 }
345
346 __attribute__((hot)) struct $thread * pop_slow(struct cluster * cltr) {
347 return search(cltr);
348 }
349#endif
350#if defined(USE_WORK_STEALING)
351 __attribute__((hot)) void push(struct cluster * cltr, struct $thread * thrd) with (cltr->ready_queue) {
352 __cfadbg_print_safe(ready_queue, "Kernel : Pushing %p on cluster %p\n", thrd, cltr);
353
354 const bool external = (!kernelTLS().this_processor) || (cltr != kernelTLS().this_processor->cltr);
355 /* paranoid */ verify(external || kernelTLS().this_processor->rdq.id < lanes.count );
356
357 // write timestamp
358 thrd->link.ts = rdtscl();
359
360 // Try to pick a lane and lock it
361 unsigned i;
362 do {
363 #if !defined(__CFA_NO_STATISTICS__)
364 if(unlikely(external)) __atomic_fetch_add(&cltr->stats->ready.push.extrn.attempt, 1, __ATOMIC_RELAXED);
365 else __tls_stats()->ready.push.local.attempt++;
366 #endif
367
368 if(unlikely(external)) {
369 i = __tls_rand() % lanes.count;
370 }
371 else {
372 processor * proc = kernelTLS().this_processor;
373 unsigned r = proc->rdq.its++;
374 i = proc->rdq.id + (r % READYQ_SHARD_FACTOR);
375 }
376
377
378 #if defined(USE_MPSC)
379 // mpsc always succeeds
380 } while( false );
381 #else
382 // If we can't lock it retry
383 } while( !__atomic_try_acquire( &lanes.data[i].lock ) );
384 #endif
385
386 // Actually push it
387 push(lanes.data[i], thrd);
388
389 #if !defined(USE_MPSC)
390 // Unlock and return
391 __atomic_unlock( &lanes.data[i].lock );
392 #endif
393
394 #if !defined(__CFA_NO_STATISTICS__)
395 if(unlikely(external)) __atomic_fetch_add(&cltr->stats->ready.push.extrn.success, 1, __ATOMIC_RELAXED);
396 else __tls_stats()->ready.push.local.success++;
397 #endif
398
399 __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);
400 }
401
402 // Pop from the ready queue from a given cluster
403 __attribute__((hot)) $thread * pop_fast(struct cluster * cltr) with (cltr->ready_queue) {
404 /* paranoid */ verify( lanes.count > 0 );
405 /* paranoid */ verify( kernelTLS().this_processor );
406 /* paranoid */ verify( kernelTLS().this_processor->rdq.id < lanes.count );
407
408 processor * proc = kernelTLS().this_processor;
409
410 if(proc->rdq.target == -1u) {
411 proc->rdq.target = __tls_rand() % lanes.count;
412 unsigned it1 = proc->rdq.itr;
413 unsigned it2 = proc->rdq.itr + 1;
414 unsigned idx1 = proc->rdq.id + (it1 % READYQ_SHARD_FACTOR);
415 unsigned idx2 = proc->rdq.id + (it2 % READYQ_SHARD_FACTOR);
416 unsigned long long tsc1 = ts(lanes.data[idx1]);
417 unsigned long long tsc2 = ts(lanes.data[idx2]);
418 proc->rdq.cutoff = min(tsc1, tsc2);
419 if(proc->rdq.cutoff == 0) proc->rdq.cutoff = -1ull;
420 }
421 else {
422 unsigned target = proc->rdq.target;
423 proc->rdq.target = -1u;
424 if(lanes.tscs[target].tv < proc->rdq.cutoff) {
425 $thread * t = try_pop(cltr, target __STATS(, __tls_stats()->ready.pop.help));
426 if(t) return t;
427 }
428 }
429
430 for(READYQ_SHARD_FACTOR) {
431 unsigned i = proc->rdq.id + (--proc->rdq.itr % READYQ_SHARD_FACTOR);
432 if($thread * t = try_pop(cltr, i __STATS(, __tls_stats()->ready.pop.local))) return t;
433 }
434 return 0p;
435 }
436
437 __attribute__((hot)) struct $thread * pop_slow(struct cluster * cltr) with (cltr->ready_queue) {
438 for(25) {
439 unsigned i = __tls_rand() % lanes.count;
440 $thread * t = try_pop(cltr, i __STATS(, __tls_stats()->ready.pop.steal));
441 if(t) return t;
442 }
443
444 return search(cltr);
445 }
446#endif
447
448//=======================================================================
449// Various Ready Queue utilities
450//=======================================================================
451// these function work the same or almost the same
452// whether they are using work-stealing or relaxed fifo scheduling
453
454//-----------------------------------------------------------------------
455// try to pop from a lane given by index w
456static inline struct $thread * try_pop(struct cluster * cltr, unsigned w __STATS(, __stats_readyQ_pop_t & stats)) with (cltr->ready_queue) {
457 __STATS( stats.attempt++; )
458
459 // Get relevant elements locally
460 __intrusive_lane_t & lane = lanes.data[w];
461
462 // If list looks empty retry
463 if( is_empty(lane) ) {
464 __STATS( stats.espec++; )
465 return 0p;
466 }
467
468 // If we can't get the lock retry
469 if( !__atomic_try_acquire(&lane.lock) ) {
470 __STATS( stats.elock++; )
471 return 0p;
472 }
473
474 // If list is empty, unlock and retry
475 if( is_empty(lane) ) {
476 __atomic_unlock(&lane.lock);
477 __STATS( stats.eempty++; )
478 return 0p;
479 }
480
481 // Actually pop the list
482 struct $thread * thrd;
483 thrd = pop(lane);
484
485 /* paranoid */ verify(thrd);
486 /* paranoid */ verify(lane.lock);
487
488 // Unlock and return
489 __atomic_unlock(&lane.lock);
490
491 // Update statistics
492 __STATS( stats.success++; )
493
494 #if defined(USE_WORK_STEALING)
495 lanes.tscs[w].tv = thrd->link.ts;
496 #endif
497
498 // return the popped thread
499 return thrd;
500}
501
502//-----------------------------------------------------------------------
503// try to pop from any lanes making sure you don't miss any threads push
504// before the start of the function
505static inline struct $thread * search(struct cluster * cltr) with (cltr->ready_queue) {
506 /* paranoid */ verify( lanes.count > 0 );
507 unsigned count = __atomic_load_n( &lanes.count, __ATOMIC_RELAXED );
508 unsigned offset = __tls_rand();
509 for(i; count) {
510 unsigned idx = (offset + i) % count;
511 struct $thread * thrd = try_pop(cltr, idx __STATS(, __tls_stats()->ready.pop.search));
512 if(thrd) {
513 return thrd;
514 }
515 }
516
517 // All lanes where empty return 0p
518 return 0p;
519}
520
521//-----------------------------------------------------------------------
522// Check that all the intrusive queues in the data structure are still consistent
523static void check( __ready_queue_t & q ) with (q) {
524 #if defined(__CFA_WITH_VERIFY__) && !defined(USE_MPSC)
525 {
526 for( idx ; lanes.count ) {
527 __intrusive_lane_t & sl = lanes.data[idx];
528 assert(!lanes.data[idx].lock);
529
530 assert(head(sl)->link.prev == 0p );
531 assert(head(sl)->link.next->link.prev == head(sl) );
532 assert(tail(sl)->link.next == 0p );
533 assert(tail(sl)->link.prev->link.next == tail(sl) );
534
535 if(is_empty(sl)) {
536 assert(tail(sl)->link.prev == head(sl));
537 assert(head(sl)->link.next == tail(sl));
538 } else {
539 assert(tail(sl)->link.prev != head(sl));
540 assert(head(sl)->link.next != tail(sl));
541 }
542 }
543 }
544 #endif
545}
546
547//-----------------------------------------------------------------------
548// Given 2 indexes, pick the list with the oldest push an try to pop from it
549static inline struct $thread * try_pop(struct cluster * cltr, unsigned i, unsigned j __STATS(, __stats_readyQ_pop_t & stats)) with (cltr->ready_queue) {
550 // Pick the bet list
551 int w = i;
552 if( __builtin_expect(!is_empty(lanes.data[j]), true) ) {
553 w = (ts(lanes.data[i]) < ts(lanes.data[j])) ? i : j;
554 }
555
556 return try_pop(cltr, w __STATS(, stats));
557}
558
559// Call this function of the intrusive list was moved using memcpy
560// fixes the list so that the pointers back to anchors aren't left dangling
561static inline void fix(__intrusive_lane_t & ll) {
562 #if !defined(USE_MPSC)
563 // if the list is not empty then follow he pointer and fix its reverse
564 if(!is_empty(ll)) {
565 head(ll)->link.next->link.prev = head(ll);
566 tail(ll)->link.prev->link.next = tail(ll);
567 }
568 // Otherwise just reset the list
569 else {
570 verify(tail(ll)->link.next == 0p);
571 tail(ll)->link.prev = head(ll);
572 head(ll)->link.next = tail(ll);
573 verify(head(ll)->link.prev == 0p);
574 }
575 #endif
576}
577
578static void assign_list(unsigned & value, dlist(processor, processor) & list, unsigned count) {
579 processor * it = &list`first;
580 for(unsigned i = 0; i < count; i++) {
581 /* paranoid */ verifyf( it, "Unexpected null iterator, at index %u of %u\n", i, count);
582 it->rdq.id = value;
583 it->rdq.target = -1u;
584 value += READYQ_SHARD_FACTOR;
585 it = &(*it)`next;
586 }
587}
588
589static void reassign_cltr_id(struct cluster * cltr) {
590 unsigned preferred = 0;
591 assign_list(preferred, cltr->procs.actives, cltr->procs.total - cltr->procs.idle);
592 assign_list(preferred, cltr->procs.idles , cltr->procs.idle );
593}
594
595static void fix_times( struct cluster * cltr ) with( cltr->ready_queue ) {
596 #if defined(USE_WORK_STEALING)
597 lanes.tscs = alloc(lanes.count, lanes.tscs`realloc);
598 for(i; lanes.count) {
599 lanes.tscs[i].tv = ts(lanes.data[i]);
600 }
601 #endif
602}
603
604// Grow the ready queue
605void ready_queue_grow(struct cluster * cltr) {
606 size_t ncount;
607 int target = cltr->procs.total;
608
609 /* paranoid */ verify( ready_mutate_islocked() );
610 __cfadbg_print_safe(ready_queue, "Kernel : Growing ready queue\n");
611
612 // Make sure that everything is consistent
613 /* paranoid */ check( cltr->ready_queue );
614
615 // grow the ready queue
616 with( cltr->ready_queue ) {
617 // Find new count
618 // Make sure we always have atleast 1 list
619 if(target >= 2) {
620 ncount = target * READYQ_SHARD_FACTOR;
621 } else {
622 ncount = SEQUENTIAL_SHARD;
623 }
624
625 // Allocate new array (uses realloc and memcpies the data)
626 lanes.data = alloc( ncount, lanes.data`realloc );
627
628 // Fix the moved data
629 for( idx; (size_t)lanes.count ) {
630 fix(lanes.data[idx]);
631 }
632
633 // Construct new data
634 for( idx; (size_t)lanes.count ~ ncount) {
635 (lanes.data[idx]){};
636 }
637
638 // Update original
639 lanes.count = ncount;
640 }
641
642 fix_times(cltr);
643
644 reassign_cltr_id(cltr);
645
646 // Make sure that everything is consistent
647 /* paranoid */ check( cltr->ready_queue );
648
649 __cfadbg_print_safe(ready_queue, "Kernel : Growing ready queue done\n");
650
651 /* paranoid */ verify( ready_mutate_islocked() );
652}
653
654// Shrink the ready queue
655void ready_queue_shrink(struct cluster * cltr) {
656 /* paranoid */ verify( ready_mutate_islocked() );
657 __cfadbg_print_safe(ready_queue, "Kernel : Shrinking ready queue\n");
658
659 // Make sure that everything is consistent
660 /* paranoid */ check( cltr->ready_queue );
661
662 int target = cltr->procs.total;
663
664 with( cltr->ready_queue ) {
665 // Remember old count
666 size_t ocount = lanes.count;
667
668 // Find new count
669 // Make sure we always have atleast 1 list
670 lanes.count = target >= 2 ? target * READYQ_SHARD_FACTOR: SEQUENTIAL_SHARD;
671 /* paranoid */ verify( ocount >= lanes.count );
672 /* paranoid */ verify( lanes.count == target * READYQ_SHARD_FACTOR || target < 2 );
673
674 // for printing count the number of displaced threads
675 #if defined(__CFA_DEBUG_PRINT__) || defined(__CFA_DEBUG_PRINT_READY_QUEUE__)
676 __attribute__((unused)) size_t displaced = 0;
677 #endif
678
679 // redistribute old data
680 for( idx; (size_t)lanes.count ~ ocount) {
681 // Lock is not strictly needed but makes checking invariants much easier
682 __attribute__((unused)) bool locked = __atomic_try_acquire(&lanes.data[idx].lock);
683 verify(locked);
684
685 // As long as we can pop from this lane to push the threads somewhere else in the queue
686 while(!is_empty(lanes.data[idx])) {
687 struct $thread * thrd;
688 thrd = pop(lanes.data[idx]);
689
690 push(cltr, thrd);
691
692 // for printing count the number of displaced threads
693 #if defined(__CFA_DEBUG_PRINT__) || defined(__CFA_DEBUG_PRINT_READY_QUEUE__)
694 displaced++;
695 #endif
696 }
697
698 // Unlock the lane
699 __atomic_unlock(&lanes.data[idx].lock);
700
701 // TODO print the queue statistics here
702
703 ^(lanes.data[idx]){};
704 }
705
706 __cfadbg_print_safe(ready_queue, "Kernel : Shrinking ready queue displaced %zu threads\n", displaced);
707
708 // Allocate new array (uses realloc and memcpies the data)
709 lanes.data = alloc( lanes.count, lanes.data`realloc );
710
711 // Fix the moved data
712 for( idx; (size_t)lanes.count ) {
713 fix(lanes.data[idx]);
714 }
715 }
716
717 fix_times(cltr);
718
719 reassign_cltr_id(cltr);
720
721 // Make sure that everything is consistent
722 /* paranoid */ check( cltr->ready_queue );
723
724 __cfadbg_print_safe(ready_queue, "Kernel : Shrinking ready queue done\n");
725 /* paranoid */ verify( ready_mutate_islocked() );
726}
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