source: libcfa/src/concurrency/ready_queue.cfa@ ce9ed84

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 ce9ed84 was f302d80, checked in by Thierry Delisle <tdelisle@…>, 4 years ago

Fix timestamp with new subqueue which was read after being cleared.
  • Property mode set to 100644
File size: 22.0 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
20#define USE_RELAXED_FIFO
21// #define USE_WORK_STEALING
22
23#include "bits/defs.hfa"
24#include "kernel_private.hfa"
25
26#define _GNU_SOURCE
27#include "stdlib.hfa"
28#include "math.hfa"
29
30#include <unistd.h>
31
32#include "ready_subqueue.hfa"
33
34static const size_t cache_line_size = 64;
35
36#if !defined(__CFA_NO_STATISTICS__)
37 #define __STATS(...) __VA_ARGS__
38#else
39 #define __STATS(...)
40#endif
41
42// No overriden function, no environment variable, no define
43// fall back to a magic number
44#ifndef __CFA_MAX_PROCESSORS__
45 #define __CFA_MAX_PROCESSORS__ 1024
46#endif
47
48#if defined(USE_RELAXED_FIFO)
49 #define BIAS 4
50 #define READYQ_SHARD_FACTOR 4
51 #define SEQUENTIAL_SHARD 1
52#elif defined(USE_WORK_STEALING)
53 #define READYQ_SHARD_FACTOR 2
54 #define SEQUENTIAL_SHARD 2
55#else
56 #error no scheduling strategy selected
57#endif
58
59static inline struct $thread * try_pop(struct cluster * cltr, unsigned w __STATS(, __stats_readyQ_pop_t & stats));
60static inline struct $thread * try_pop(struct cluster * cltr, unsigned i, unsigned j __STATS(, __stats_readyQ_pop_t & stats));
61static inline struct $thread * search(struct cluster * cltr);
62static inline [unsigned, bool] idx_from_r(unsigned r, unsigned preferred);
63
64
65// returns the maximum number of processors the RWLock support
66__attribute__((weak)) unsigned __max_processors() {
67 const char * max_cores_s = getenv("CFA_MAX_PROCESSORS");
68 if(!max_cores_s) {
69 __cfadbg_print_nolock(ready_queue, "No CFA_MAX_PROCESSORS in ENV\n");
70 return __CFA_MAX_PROCESSORS__;
71 }
72
73 char * endptr = 0p;
74 long int max_cores_l = strtol(max_cores_s, &endptr, 10);
75 if(max_cores_l < 1 || max_cores_l > 65535) {
76 __cfadbg_print_nolock(ready_queue, "CFA_MAX_PROCESSORS out of range : %ld\n", max_cores_l);
77 return __CFA_MAX_PROCESSORS__;
78 }
79 if('\0' != *endptr) {
80 __cfadbg_print_nolock(ready_queue, "CFA_MAX_PROCESSORS not a decimal number : %s\n", max_cores_s);
81 return __CFA_MAX_PROCESSORS__;
82 }
83
84 return max_cores_l;
85}
86
87//=======================================================================
88// Cluster wide reader-writer lock
89//=======================================================================
90void ?{}(__scheduler_RWLock_t & this) {
91 this.max = __max_processors();
92 this.alloc = 0;
93 this.ready = 0;
94 this.data = alloc(this.max);
95 this.write_lock = false;
96
97 /*paranoid*/ verify(__atomic_is_lock_free(sizeof(this.alloc), &this.alloc));
98 /*paranoid*/ verify(__atomic_is_lock_free(sizeof(this.ready), &this.ready));
99
100}
101void ^?{}(__scheduler_RWLock_t & this) {
102 free(this.data);
103}
104
105
106//=======================================================================
107// Lock-Free registering/unregistering of threads
108unsigned register_proc_id( void ) with(*__scheduler_lock) {
109 __cfadbg_print_safe(ready_queue, "Kernel : Registering proc %p for RW-Lock\n", proc);
110 bool * handle = (bool *)&kernelTLS().sched_lock;
111
112 // Step - 1 : check if there is already space in the data
113 uint_fast32_t s = ready;
114
115 // Check among all the ready
116 for(uint_fast32_t i = 0; i < s; i++) {
117 bool * volatile * cell = (bool * volatile *)&data[i]; // Cforall is bugged and the double volatiles causes problems
118 /* paranoid */ verify( handle != *cell );
119
120 bool * null = 0p; // Re-write every loop since compare thrashes it
121 if( __atomic_load_n(cell, (int)__ATOMIC_RELAXED) == null
122 && __atomic_compare_exchange_n( cell, &null, handle, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
123 /* paranoid */ verify(i < ready);
124 /* paranoid */ verify( (kernelTLS().sched_id = i, true) );
125 return i;
126 }
127 }
128
129 if(max <= alloc) abort("Trying to create more than %ud processors", __scheduler_lock->max);
130
131 // Step - 2 : F&A to get a new spot in the array.
132 uint_fast32_t n = __atomic_fetch_add(&alloc, 1, __ATOMIC_SEQ_CST);
133 if(max <= n) abort("Trying to create more than %ud processors", __scheduler_lock->max);
134
135 // Step - 3 : Mark space as used and then publish it.
136 data[n] = handle;
137 while() {
138 unsigned copy = n;
139 if( __atomic_load_n(&ready, __ATOMIC_RELAXED) == n
140 && __atomic_compare_exchange_n(&ready, &copy, n + 1, true, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST))
141 break;
142 Pause();
143 }
144
145 __cfadbg_print_safe(ready_queue, "Kernel : Registering proc %p done, id %lu\n", proc, n);
146
147 // Return new spot.
148 /* paranoid */ verify(n < ready);
149 /* paranoid */ verify( (kernelTLS().sched_id = n, true) );
150 return n;
151}
152
153void unregister_proc_id( unsigned id ) with(*__scheduler_lock) {
154 /* paranoid */ verify(id < ready);
155 /* paranoid */ verify(id == kernelTLS().sched_id);
156 /* paranoid */ verify(data[id] == &kernelTLS().sched_lock);
157
158 bool * volatile * cell = (bool * volatile *)&data[id]; // Cforall is bugged and the double volatiles causes problems
159
160 __atomic_store_n(cell, 0p, __ATOMIC_RELEASE);
161
162 __cfadbg_print_safe(ready_queue, "Kernel : Unregister proc %p\n", proc);
163}
164
165//-----------------------------------------------------------------------
166// Writer side : acquire when changing the ready queue, e.g. adding more
167// queues or removing them.
168uint_fast32_t ready_mutate_lock( void ) with(*__scheduler_lock) {
169 /* paranoid */ verify( ! __preemption_enabled() );
170 /* paranoid */ verify( ! kernelTLS().sched_lock );
171
172 // Step 1 : lock global lock
173 // It is needed to avoid processors that register mid Critical-Section
174 // to simply lock their own lock and enter.
175 __atomic_acquire( &write_lock );
176
177 // Step 2 : lock per-proc lock
178 // Processors that are currently being registered aren't counted
179 // but can't be in read_lock or in the critical section.
180 // All other processors are counted
181 uint_fast32_t s = ready;
182 for(uint_fast32_t i = 0; i < s; i++) {
183 volatile bool * llock = data[i];
184 if(llock) __atomic_acquire( llock );
185 }
186
187 /* paranoid */ verify( ! __preemption_enabled() );
188 return s;
189}
190
191void ready_mutate_unlock( uint_fast32_t last_s ) with(*__scheduler_lock) {
192 /* paranoid */ verify( ! __preemption_enabled() );
193
194 // Step 1 : release local locks
195 // This must be done while the global lock is held to avoid
196 // threads that where created mid critical section
197 // to race to lock their local locks and have the writer
198 // immidiately unlock them
199 // Alternative solution : return s in write_lock and pass it to write_unlock
200 for(uint_fast32_t i = 0; i < last_s; i++) {
201 volatile bool * llock = data[i];
202 if(llock) __atomic_store_n(llock, (bool)false, __ATOMIC_RELEASE);
203 }
204
205 // Step 2 : release global lock
206 /*paranoid*/ assert(true == write_lock);
207 __atomic_store_n(&write_lock, (bool)false, __ATOMIC_RELEASE);
208
209 /* paranoid */ verify( ! __preemption_enabled() );
210}
211
212//=======================================================================
213// Cforall Ready Queue used for scheduling
214//=======================================================================
215void ?{}(__ready_queue_t & this) with (this) {
216 lanes.data = 0p;
217 lanes.tscs = 0p;
218 lanes.count = 0;
219}
220
221void ^?{}(__ready_queue_t & this) with (this) {
222 verify( SEQUENTIAL_SHARD == lanes.count );
223 free(lanes.data);
224 free(lanes.tscs);
225}
226
227//-----------------------------------------------------------------------
228#if defined(USE_RELAXED_FIFO)
229 //-----------------------------------------------------------------------
230 // get index from random number with or without bias towards queues
231 static inline [unsigned, bool] idx_from_r(unsigned r, unsigned preferred) {
232 unsigned i;
233 bool local;
234 unsigned rlow = r % BIAS;
235 unsigned rhigh = r / BIAS;
236 if((0 != rlow) && preferred >= 0) {
237 // (BIAS - 1) out of BIAS chances
238 // Use perferred queues
239 i = preferred + (rhigh % READYQ_SHARD_FACTOR);
240 local = true;
241 }
242 else {
243 // 1 out of BIAS chances
244 // Use all queues
245 i = rhigh;
246 local = false;
247 }
248 return [i, local];
249 }
250
251 __attribute__((hot)) void push(struct cluster * cltr, struct $thread * thrd) with (cltr->ready_queue) {
252 __cfadbg_print_safe(ready_queue, "Kernel : Pushing %p on cluster %p\n", thrd, cltr);
253
254 const bool external = (!kernelTLS().this_processor) || (cltr != kernelTLS().this_processor->cltr);
255 /* paranoid */ verify(external || kernelTLS().this_processor->rdq.id < lanes.count );
256
257 bool local;
258 int preferred = external ? -1 : kernelTLS().this_processor->rdq.id;
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_fwd();
265 [i, local] = idx_from_r(r, preferred);
266
267 i %= __atomic_load_n( &lanes.count, __ATOMIC_RELAXED );
268
269 #if !defined(__CFA_NO_STATISTICS__)
270 if(unlikely(external)) __atomic_fetch_add(&cltr->stats->ready.push.extrn.attempt, 1, __ATOMIC_RELAXED);
271 else if(local) __tls_stats()->ready.push.local.attempt++;
272 else __tls_stats()->ready.push.share.attempt++;
273 #endif
274
275 // If we can't lock it retry
276 } while( !__atomic_try_acquire( &lanes.data[i].lock ) );
277
278 // Actually push it
279 push(lanes.data[i], thrd);
280
281 // Unlock and return
282 __atomic_unlock( &lanes.data[i].lock );
283
284 // Mark the current index in the tls rng instance as having an item
285 __tls_rand_advance_bck();
286
287 __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);
288
289 // Update statistics
290 #if !defined(__CFA_NO_STATISTICS__)
291 if(unlikely(external)) __atomic_fetch_add(&cltr->stats->ready.push.extrn.success, 1, __ATOMIC_RELAXED);
292 else if(local) __tls_stats()->ready.push.local.success++;
293 else __tls_stats()->ready.push.share.success++;
294 #endif
295 }
296
297 // Pop from the ready queue from a given cluster
298 __attribute__((hot)) $thread * pop_fast(struct cluster * cltr) with (cltr->ready_queue) {
299 /* paranoid */ verify( lanes.count > 0 );
300 /* paranoid */ verify( kernelTLS().this_processor );
301 /* paranoid */ verify( kernelTLS().this_processor->rdq.id < lanes.count );
302
303 unsigned count = __atomic_load_n( &lanes.count, __ATOMIC_RELAXED );
304 int preferred = kernelTLS().this_processor->rdq.id;
305
306
307 // As long as the list is not empty, try finding a lane that isn't empty and pop from it
308 for(25) {
309 // Pick two lists at random
310 unsigned ri = __tls_rand_bck();
311 unsigned rj = __tls_rand_bck();
312
313 unsigned i, j;
314 __attribute__((unused)) bool locali, localj;
315 [i, locali] = idx_from_r(ri, preferred);
316 [j, localj] = idx_from_r(rj, preferred);
317
318 i %= count;
319 j %= count;
320
321 // try popping from the 2 picked lists
322 struct $thread * thrd = try_pop(cltr, i, j __STATS(, *(locali || localj ? &__tls_stats()->ready.pop.local : &__tls_stats()->ready.pop.help)));
323 if(thrd) {
324 return thrd;
325 }
326 }
327
328 // All lanes where empty return 0p
329 return 0p;
330 }
331
332 __attribute__((hot)) struct $thread * pop_slow(struct cluster * cltr) { return pop_fast(cltr); }
333 __attribute__((hot)) struct $thread * pop_search(struct cluster * cltr) {
334 return search(cltr);
335 }
336#endif
337#if defined(USE_WORK_STEALING)
338 __attribute__((hot)) void push(struct cluster * cltr, struct $thread * thrd) with (cltr->ready_queue) {
339 __cfadbg_print_safe(ready_queue, "Kernel : Pushing %p on cluster %p\n", thrd, cltr);
340
341 // #define USE_PREFERRED
342 #if !defined(USE_PREFERRED)
343 const bool external = (!kernelTLS().this_processor) || (cltr != kernelTLS().this_processor->cltr);
344 /* paranoid */ verify(external || kernelTLS().this_processor->rdq.id < lanes.count );
345 #else
346 unsigned preferred = thrd->preferred;
347 const bool external = (!kernelTLS().this_processor) || preferred == -1u || thrd->curr_cluster != cltr;
348 /* paranoid */ verifyf(external || preferred < lanes.count, "Invalid preferred queue %u for %u lanes", preferred, lanes.count );
349
350 unsigned r = preferred % READYQ_SHARD_FACTOR;
351 const unsigned start = preferred - r;
352 #endif
353
354 // Try to pick a lane and lock it
355 unsigned i;
356 do {
357 #if !defined(__CFA_NO_STATISTICS__)
358 if(unlikely(external)) __atomic_fetch_add(&cltr->stats->ready.push.extrn.attempt, 1, __ATOMIC_RELAXED);
359 else __tls_stats()->ready.push.local.attempt++;
360 #endif
361
362 if(unlikely(external)) {
363 i = __tls_rand() % lanes.count;
364 }
365 else {
366 #if !defined(USE_PREFERRED)
367 processor * proc = kernelTLS().this_processor;
368 unsigned r = proc->rdq.its++;
369 i = proc->rdq.id + (r % READYQ_SHARD_FACTOR);
370 #else
371 i = start + (r++ % READYQ_SHARD_FACTOR);
372 #endif
373 }
374 // If we can't lock it retry
375 } while( !__atomic_try_acquire( &lanes.data[i].lock ) );
376
377 // Actually push it
378 push(lanes.data[i], thrd);
379
380 // Unlock and return
381 __atomic_unlock( &lanes.data[i].lock );
382
383 #if !defined(__CFA_NO_STATISTICS__)
384 if(unlikely(external)) __atomic_fetch_add(&cltr->stats->ready.push.extrn.success, 1, __ATOMIC_RELAXED);
385 else __tls_stats()->ready.push.local.success++;
386 #endif
387
388 __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);
389 }
390
391 // Pop from the ready queue from a given cluster
392 __attribute__((hot)) $thread * pop_fast(struct cluster * cltr) with (cltr->ready_queue) {
393 /* paranoid */ verify( lanes.count > 0 );
394 /* paranoid */ verify( kernelTLS().this_processor );
395 /* paranoid */ verify( kernelTLS().this_processor->rdq.id < lanes.count );
396
397 processor * proc = kernelTLS().this_processor;
398
399 if(proc->rdq.target == -1u) {
400 _Static_assert(READYQ_SHARD_FACTOR == 2);
401 unsigned idx1 = proc->rdq.id + 0;
402 unsigned idx2 = proc->rdq.id + 1;
403 unsigned long long tsc1 = ts(lanes.data[idx1]);
404 unsigned long long tsc2 = ts(lanes.data[idx2]);
405 proc->rdq.target = __tls_rand() % lanes.count;
406
407 // WARNING: std::min is polymorphic and therefore causes 500% slowdown instead of the expected 2%
408 proc->rdq.cutoff = tsc1 < tsc2 ? tsc1 : tsc2;
409 }
410 else {
411 unsigned target = proc->rdq.target;
412 proc->rdq.target = -1u;
413 if(lanes.tscs[target].tv < proc->rdq.cutoff) {
414 $thread * t = try_pop(cltr, target __STATS(, __tls_stats()->ready.pop.help));
415 if(t) return t;
416 }
417 }
418
419 for(READYQ_SHARD_FACTOR) {
420 unsigned i = proc->rdq.id + (proc->rdq.itr++ % READYQ_SHARD_FACTOR);
421 if($thread * t = try_pop(cltr, i __STATS(, __tls_stats()->ready.pop.local))) return t;
422 }
423 return 0p;
424 }
425
426 __attribute__((hot)) struct $thread * pop_slow(struct cluster * cltr) with (cltr->ready_queue) {
427 unsigned i = __tls_rand() % lanes.count;
428 return try_pop(cltr, i __STATS(, __tls_stats()->ready.pop.steal));
429 }
430
431 __attribute__((hot)) struct $thread * pop_search(struct cluster * cltr) with (cltr->ready_queue) {
432 return search(cltr);
433 }
434#endif
435
436//=======================================================================
437// Various Ready Queue utilities
438//=======================================================================
439// these function work the same or almost the same
440// whether they are using work-stealing or relaxed fifo scheduling
441
442//-----------------------------------------------------------------------
443// try to pop from a lane given by index w
444static inline struct $thread * try_pop(struct cluster * cltr, unsigned w __STATS(, __stats_readyQ_pop_t & stats)) with (cltr->ready_queue) {
445 __STATS( stats.attempt++; )
446
447 // Get relevant elements locally
448 __intrusive_lane_t & lane = lanes.data[w];
449
450 // If list looks empty retry
451 if( is_empty(lane) ) {
452 __STATS( stats.espec++; )
453 return 0p;
454 }
455
456 // If we can't get the lock retry
457 if( !__atomic_try_acquire(&lane.lock) ) {
458 __STATS( stats.elock++; )
459 return 0p;
460 }
461
462 // If list is empty, unlock and retry
463 if( is_empty(lane) ) {
464 __atomic_unlock(&lane.lock);
465 __STATS( stats.eempty++; )
466 return 0p;
467 }
468
469 // Actually pop the list
470 struct $thread * thrd;
471 unsigned long long tsv;
472 [thrd, tsv] = pop(lane);
473
474 /* paranoid */ verify(thrd);
475 /* paranoid */ verify(lane.lock);
476
477 // Unlock and return
478 __atomic_unlock(&lane.lock);
479
480 // Update statistics
481 __STATS( stats.success++; )
482
483 #if defined(USE_WORK_STEALING)
484 lanes.tscs[w].tv = tsv;
485 #endif
486
487 thrd->preferred = w;
488
489 // return the popped thread
490 return thrd;
491}
492
493//-----------------------------------------------------------------------
494// try to pop from any lanes making sure you don't miss any threads push
495// before the start of the function
496static inline struct $thread * search(struct cluster * cltr) with (cltr->ready_queue) {
497 /* paranoid */ verify( lanes.count > 0 );
498 unsigned count = __atomic_load_n( &lanes.count, __ATOMIC_RELAXED );
499 unsigned offset = __tls_rand();
500 for(i; count) {
501 unsigned idx = (offset + i) % count;
502 struct $thread * thrd = try_pop(cltr, idx __STATS(, __tls_stats()->ready.pop.search));
503 if(thrd) {
504 return thrd;
505 }
506 }
507
508 // All lanes where empty return 0p
509 return 0p;
510}
511
512//-----------------------------------------------------------------------
513// Check that all the intrusive queues in the data structure are still consistent
514static void check( __ready_queue_t & q ) with (q) {
515 #if defined(__CFA_WITH_VERIFY__)
516 {
517 for( idx ; lanes.count ) {
518 __intrusive_lane_t & sl = lanes.data[idx];
519 assert(!lanes.data[idx].lock);
520
521 if(is_empty(sl)) {
522 assert( sl.anchor.next == 0p );
523 assert( sl.anchor.ts == 0 );
524 assert( mock_head(sl) == sl.prev );
525 } else {
526 assert( sl.anchor.next != 0p );
527 assert( sl.anchor.ts != 0 );
528 assert( mock_head(sl) != sl.prev );
529 }
530 }
531 }
532 #endif
533}
534
535//-----------------------------------------------------------------------
536// Given 2 indexes, pick the list with the oldest push an try to pop from it
537static inline struct $thread * try_pop(struct cluster * cltr, unsigned i, unsigned j __STATS(, __stats_readyQ_pop_t & stats)) with (cltr->ready_queue) {
538 // Pick the bet list
539 int w = i;
540 if( __builtin_expect(!is_empty(lanes.data[j]), true) ) {
541 w = (ts(lanes.data[i]) < ts(lanes.data[j])) ? i : j;
542 }
543
544 return try_pop(cltr, w __STATS(, stats));
545}
546
547// Call this function of the intrusive list was moved using memcpy
548// fixes the list so that the pointers back to anchors aren't left dangling
549static inline void fix(__intrusive_lane_t & ll) {
550 if(is_empty(ll)) {
551 verify(ll.anchor.next == 0p);
552 ll.prev = mock_head(ll);
553 }
554}
555
556static void assign_list(unsigned & value, dlist(processor, processor) & list, unsigned count) {
557 processor * it = &list`first;
558 for(unsigned i = 0; i < count; i++) {
559 /* paranoid */ verifyf( it, "Unexpected null iterator, at index %u of %u\n", i, count);
560 it->rdq.id = value;
561 it->rdq.target = -1u;
562 value += READYQ_SHARD_FACTOR;
563 it = &(*it)`next;
564 }
565}
566
567static void reassign_cltr_id(struct cluster * cltr) {
568 unsigned preferred = 0;
569 assign_list(preferred, cltr->procs.actives, cltr->procs.total - cltr->procs.idle);
570 assign_list(preferred, cltr->procs.idles , cltr->procs.idle );
571}
572
573static void fix_times( struct cluster * cltr ) with( cltr->ready_queue ) {
574 #if defined(USE_WORK_STEALING)
575 lanes.tscs = alloc(lanes.count, lanes.tscs`realloc);
576 for(i; lanes.count) {
577 lanes.tscs[i].tv = ts(lanes.data[i]);
578 }
579 #endif
580}
581
582// Grow the ready queue
583void ready_queue_grow(struct cluster * cltr) {
584 size_t ncount;
585 int target = cltr->procs.total;
586
587 /* paranoid */ verify( ready_mutate_islocked() );
588 __cfadbg_print_safe(ready_queue, "Kernel : Growing ready queue\n");
589
590 // Make sure that everything is consistent
591 /* paranoid */ check( cltr->ready_queue );
592
593 // grow the ready queue
594 with( cltr->ready_queue ) {
595 // Find new count
596 // Make sure we always have atleast 1 list
597 if(target >= 2) {
598 ncount = target * READYQ_SHARD_FACTOR;
599 } else {
600 ncount = SEQUENTIAL_SHARD;
601 }
602
603 // Allocate new array (uses realloc and memcpies the data)
604 lanes.data = alloc( ncount, lanes.data`realloc );
605
606 // Fix the moved data
607 for( idx; (size_t)lanes.count ) {
608 fix(lanes.data[idx]);
609 }
610
611 // Construct new data
612 for( idx; (size_t)lanes.count ~ ncount) {
613 (lanes.data[idx]){};
614 }
615
616 // Update original
617 lanes.count = ncount;
618 }
619
620 fix_times(cltr);
621
622 reassign_cltr_id(cltr);
623
624 // Make sure that everything is consistent
625 /* paranoid */ check( cltr->ready_queue );
626
627 __cfadbg_print_safe(ready_queue, "Kernel : Growing ready queue done\n");
628
629 /* paranoid */ verify( ready_mutate_islocked() );
630}
631
632// Shrink the ready queue
633void ready_queue_shrink(struct cluster * cltr) {
634 /* paranoid */ verify( ready_mutate_islocked() );
635 __cfadbg_print_safe(ready_queue, "Kernel : Shrinking ready queue\n");
636
637 // Make sure that everything is consistent
638 /* paranoid */ check( cltr->ready_queue );
639
640 int target = cltr->procs.total;
641
642 with( cltr->ready_queue ) {
643 // Remember old count
644 size_t ocount = lanes.count;
645
646 // Find new count
647 // Make sure we always have atleast 1 list
648 lanes.count = target >= 2 ? target * READYQ_SHARD_FACTOR: SEQUENTIAL_SHARD;
649 /* paranoid */ verify( ocount >= lanes.count );
650 /* paranoid */ verify( lanes.count == target * READYQ_SHARD_FACTOR || target < 2 );
651
652 // for printing count the number of displaced threads
653 #if defined(__CFA_DEBUG_PRINT__) || defined(__CFA_DEBUG_PRINT_READY_QUEUE__)
654 __attribute__((unused)) size_t displaced = 0;
655 #endif
656
657 // redistribute old data
658 for( idx; (size_t)lanes.count ~ ocount) {
659 // Lock is not strictly needed but makes checking invariants much easier
660 __attribute__((unused)) bool locked = __atomic_try_acquire(&lanes.data[idx].lock);
661 verify(locked);
662
663 // As long as we can pop from this lane to push the threads somewhere else in the queue
664 while(!is_empty(lanes.data[idx])) {
665 struct $thread * thrd;
666 unsigned long long _;
667 [thrd, _] = pop(lanes.data[idx]);
668
669 push(cltr, thrd);
670
671 // for printing count the number of displaced threads
672 #if defined(__CFA_DEBUG_PRINT__) || defined(__CFA_DEBUG_PRINT_READY_QUEUE__)
673 displaced++;
674 #endif
675 }
676
677 // Unlock the lane
678 __atomic_unlock(&lanes.data[idx].lock);
679
680 // TODO print the queue statistics here
681
682 ^(lanes.data[idx]){};
683 }
684
685 __cfadbg_print_safe(ready_queue, "Kernel : Shrinking ready queue displaced %zu threads\n", displaced);
686
687 // Allocate new array (uses realloc and memcpies the data)
688 lanes.data = alloc( lanes.count, lanes.data`realloc );
689
690 // Fix the moved data
691 for( idx; (size_t)lanes.count ) {
692 fix(lanes.data[idx]);
693 }
694 }
695
696 fix_times(cltr);
697
698 reassign_cltr_id(cltr);
699
700 // Make sure that everything is consistent
701 /* paranoid */ check( cltr->ready_queue );
702
703 __cfadbg_print_safe(ready_queue, "Kernel : Shrinking ready queue done\n");
704 /* paranoid */ verify( ready_mutate_islocked() );
705}
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