source: libcfa/src/concurrency/ready_queue.cfa @ c993b15

arm-ehjacob/cs343-translationnew-ast-unique-expr
Last change on this file since c993b15 was c993b15, checked in by Thierry Delisle <tdelisle@…>, 7 months ago

Changed RW lock to avoid hitting the global array on schedule.

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