source: libcfa/src/concurrency/ready_queue.cfa @ 43784ac

jacob/cs343-translationnew-ast-unique-expr
Last change on this file since 43784ac was 43784ac, checked in by Thierry Delisle <tdelisle@…>, 4 months ago

Changed libcfathread to consistently define _GNU_SOURCE

  • 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 _GNU_SOURCE
18
19// #define __CFA_DEBUG_PRINT_READY_QUEUE__
20
21
22#define USE_RELAXED_FIFO
23// #define USE_WORK_STEALING
24
25#include "bits/defs.hfa"
26#include "kernel_private.hfa"
27
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, bool push_local) with (cltr->ready_queue) {
253                __cfadbg_print_safe(ready_queue, "Kernel : Pushing %p on cluster %p\n", thrd, cltr);
254
255                const bool external = !push_local || (!kernelTLS().this_processor) || (cltr != kernelTLS().this_processor->cltr);
256                /* paranoid */ verify(external || kernelTLS().this_processor->rdq.id < lanes.count );
257
258                bool local;
259                int preferred = external ? -1 : kernelTLS().this_processor->rdq.id;
260
261                // Try to pick a lane and lock it
262                unsigned i;
263                do {
264                        // Pick the index of a lane
265                        unsigned r = __tls_rand_fwd();
266                        [i, local] = idx_from_r(r, preferred);
267
268                        i %= __atomic_load_n( &lanes.count, __ATOMIC_RELAXED );
269
270                        #if !defined(__CFA_NO_STATISTICS__)
271                                if(unlikely(external)) __atomic_fetch_add(&cltr->stats->ready.push.extrn.attempt, 1, __ATOMIC_RELAXED);
272                                else if(local) __tls_stats()->ready.push.local.attempt++;
273                                else __tls_stats()->ready.push.share.attempt++;
274                        #endif
275
276                        // If we can't lock it retry
277                } while( !__atomic_try_acquire( &lanes.data[i].lock ) );
278
279                // Actually push it
280                push(lanes.data[i], thrd);
281
282                // Unlock and return
283                __atomic_unlock( &lanes.data[i].lock );
284
285                // Mark the current index in the tls rng instance as having an item
286                __tls_rand_advance_bck();
287
288                __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);
289
290                // Update statistics
291                #if !defined(__CFA_NO_STATISTICS__)
292                        if(unlikely(external)) __atomic_fetch_add(&cltr->stats->ready.push.extrn.success, 1, __ATOMIC_RELAXED);
293                        else if(local) __tls_stats()->ready.push.local.success++;
294                        else __tls_stats()->ready.push.share.success++;
295                #endif
296        }
297
298        // Pop from the ready queue from a given cluster
299        __attribute__((hot)) $thread * pop_fast(struct cluster * cltr) with (cltr->ready_queue) {
300                /* paranoid */ verify( lanes.count > 0 );
301                /* paranoid */ verify( kernelTLS().this_processor );
302                /* paranoid */ verify( kernelTLS().this_processor->rdq.id < lanes.count );
303
304                unsigned count = __atomic_load_n( &lanes.count, __ATOMIC_RELAXED );
305                int preferred = kernelTLS().this_processor->rdq.id;
306
307
308                // As long as the list is not empty, try finding a lane that isn't empty and pop from it
309                for(25) {
310                        // Pick two lists at random
311                        unsigned ri = __tls_rand_bck();
312                        unsigned rj = __tls_rand_bck();
313
314                        unsigned i, j;
315                        __attribute__((unused)) bool locali, localj;
316                        [i, locali] = idx_from_r(ri, preferred);
317                        [j, localj] = idx_from_r(rj, preferred);
318
319                        i %= count;
320                        j %= count;
321
322                        // try popping from the 2 picked lists
323                        struct $thread * thrd = try_pop(cltr, i, j __STATS(, *(locali || localj ? &__tls_stats()->ready.pop.local : &__tls_stats()->ready.pop.help)));
324                        if(thrd) {
325                                return thrd;
326                        }
327                }
328
329                // All lanes where empty return 0p
330                return 0p;
331        }
332
333        __attribute__((hot)) struct $thread * pop_slow(struct cluster * cltr) { return pop_fast(cltr); }
334        __attribute__((hot)) struct $thread * pop_search(struct cluster * cltr) {
335                return search(cltr);
336        }
337#endif
338#if defined(USE_WORK_STEALING)
339        __attribute__((hot)) void push(struct cluster * cltr, struct $thread * thrd, bool push_local) with (cltr->ready_queue) {
340                __cfadbg_print_safe(ready_queue, "Kernel : Pushing %p on cluster %p\n", thrd, cltr);
341
342                // #define USE_PREFERRED
343                #if !defined(USE_PREFERRED)
344                const bool external = !push_local || (!kernelTLS().this_processor) || (cltr != kernelTLS().this_processor->cltr);
345                /* paranoid */ verify(external || kernelTLS().this_processor->rdq.id < lanes.count );
346                #else
347                        unsigned preferred = thrd->preferred;
348                        const bool external = push_local || (!kernelTLS().this_processor) || preferred == -1u || thrd->curr_cluster != cltr;
349                        /* paranoid */ verifyf(external || preferred < lanes.count, "Invalid preferred queue %u for %u lanes", preferred, lanes.count );
350
351                        unsigned r = preferred % READYQ_SHARD_FACTOR;
352                        const unsigned start = preferred - r;
353                #endif
354
355                // Try to pick a lane and lock it
356                unsigned i;
357                do {
358                        #if !defined(__CFA_NO_STATISTICS__)
359                                if(unlikely(external)) __atomic_fetch_add(&cltr->stats->ready.push.extrn.attempt, 1, __ATOMIC_RELAXED);
360                                else __tls_stats()->ready.push.local.attempt++;
361                        #endif
362
363                        if(unlikely(external)) {
364                                i = __tls_rand() % lanes.count;
365                        }
366                        else {
367                                #if !defined(USE_PREFERRED)
368                                        processor * proc = kernelTLS().this_processor;
369                                        unsigned r = proc->rdq.its++;
370                                        i =  proc->rdq.id + (r % READYQ_SHARD_FACTOR);
371                                #else
372                                        i = start + (r++ % READYQ_SHARD_FACTOR);
373                                #endif
374                        }
375                        // If we can't lock it retry
376                } while( !__atomic_try_acquire( &lanes.data[i].lock ) );
377
378                // Actually push it
379                push(lanes.data[i], thrd);
380
381                // Unlock and return
382                __atomic_unlock( &lanes.data[i].lock );
383
384                #if !defined(__CFA_NO_STATISTICS__)
385                        if(unlikely(external)) __atomic_fetch_add(&cltr->stats->ready.push.extrn.success, 1, __ATOMIC_RELAXED);
386                        else __tls_stats()->ready.push.local.success++;
387                #endif
388
389                __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);
390        }
391
392        // Pop from the ready queue from a given cluster
393        __attribute__((hot)) $thread * pop_fast(struct cluster * cltr) with (cltr->ready_queue) {
394                /* paranoid */ verify( lanes.count > 0 );
395                /* paranoid */ verify( kernelTLS().this_processor );
396                /* paranoid */ verify( kernelTLS().this_processor->rdq.id < lanes.count );
397
398                processor * proc = kernelTLS().this_processor;
399
400                if(proc->rdq.target == -1u) {
401                        unsigned long long min = ts(lanes.data[proc->rdq.id]);
402                        for(int i = 0; i < READYQ_SHARD_FACTOR; i++) {
403                                unsigned long long tsc = ts(lanes.data[proc->rdq.id + i]);
404                                if(tsc < min) min = tsc;
405                        }
406                        proc->rdq.cutoff = min;
407                        proc->rdq.target = __tls_rand() % lanes.count;
408                }
409                else {
410                        unsigned target = proc->rdq.target;
411                        proc->rdq.target = -1u;
412                        const unsigned long long bias = 0; //2_500_000_000;
413                        const unsigned long long cutoff = proc->rdq.cutoff > bias ? proc->rdq.cutoff - bias : proc->rdq.cutoff;
414                        if(lanes.tscs[target].tv < cutoff && ts(lanes.data[target]) < cutoff) {
415                                $thread * t = try_pop(cltr, target __STATS(, __tls_stats()->ready.pop.help));
416                                if(t) return t;
417                        }
418                }
419
420                for(READYQ_SHARD_FACTOR) {
421                        unsigned i = proc->rdq.id + (proc->rdq.itr++ % READYQ_SHARD_FACTOR);
422                        if($thread * t = try_pop(cltr, i __STATS(, __tls_stats()->ready.pop.local))) return t;
423                }
424                return 0p;
425        }
426
427        __attribute__((hot)) struct $thread * pop_slow(struct cluster * cltr) with (cltr->ready_queue) {
428                unsigned i = __tls_rand() % lanes.count;
429                return try_pop(cltr, i __STATS(, __tls_stats()->ready.pop.steal));
430        }
431
432        __attribute__((hot)) struct $thread * pop_search(struct cluster * cltr) with (cltr->ready_queue) {
433                return search(cltr);
434        }
435#endif
436
437//=======================================================================
438// Various Ready Queue utilities
439//=======================================================================
440// these function work the same or almost the same
441// whether they are using work-stealing or relaxed fifo scheduling
442
443//-----------------------------------------------------------------------
444// try to pop from a lane given by index w
445static inline struct $thread * try_pop(struct cluster * cltr, unsigned w __STATS(, __stats_readyQ_pop_t & stats)) with (cltr->ready_queue) {
446        __STATS( stats.attempt++; )
447
448        // Get relevant elements locally
449        __intrusive_lane_t & lane = lanes.data[w];
450
451        // If list looks empty retry
452        if( is_empty(lane) ) {
453                return 0p;
454        }
455
456        // If we can't get the lock retry
457        if( !__atomic_try_acquire(&lane.lock) ) {
458                return 0p;
459        }
460
461        // If list is empty, unlock and retry
462        if( is_empty(lane) ) {
463                __atomic_unlock(&lane.lock);
464                return 0p;
465        }
466
467        // Actually pop the list
468        struct $thread * thrd;
469        unsigned long long tsv;
470        [thrd, tsv] = pop(lane);
471
472        /* paranoid */ verify(thrd);
473        /* paranoid */ verify(tsv);
474        /* paranoid */ verify(lane.lock);
475
476        // Unlock and return
477        __atomic_unlock(&lane.lock);
478
479        // Update statistics
480        __STATS( stats.success++; )
481
482        #if defined(USE_WORK_STEALING)
483                lanes.tscs[w].tv = tsv;
484        #endif
485
486        thrd->preferred = w;
487
488        // return the popped thread
489        return thrd;
490}
491
492//-----------------------------------------------------------------------
493// try to pop from any lanes making sure you don't miss any threads push
494// before the start of the function
495static inline struct $thread * search(struct cluster * cltr) with (cltr->ready_queue) {
496        /* paranoid */ verify( lanes.count > 0 );
497        unsigned count = __atomic_load_n( &lanes.count, __ATOMIC_RELAXED );
498        unsigned offset = __tls_rand();
499        for(i; count) {
500                unsigned idx = (offset + i) % count;
501                struct $thread * thrd = try_pop(cltr, idx __STATS(, __tls_stats()->ready.pop.search));
502                if(thrd) {
503                        return thrd;
504                }
505        }
506
507        // All lanes where empty return 0p
508        return 0p;
509}
510
511//-----------------------------------------------------------------------
512// Check that all the intrusive queues in the data structure are still consistent
513static void check( __ready_queue_t & q ) with (q) {
514        #if defined(__CFA_WITH_VERIFY__)
515                {
516                        for( idx ; lanes.count ) {
517                                __intrusive_lane_t & sl = lanes.data[idx];
518                                assert(!lanes.data[idx].lock);
519
520                                        if(is_empty(sl)) {
521                                                assert( sl.anchor.next == 0p );
522                                                assert( sl.anchor.ts   == 0  );
523                                                assert( mock_head(sl)  == sl.prev );
524                                        } else {
525                                                assert( sl.anchor.next != 0p );
526                                                assert( sl.anchor.ts   != 0  );
527                                                assert( mock_head(sl)  != sl.prev );
528                                        }
529                        }
530                }
531        #endif
532}
533
534//-----------------------------------------------------------------------
535// Given 2 indexes, pick the list with the oldest push an try to pop from it
536static inline struct $thread * try_pop(struct cluster * cltr, unsigned i, unsigned j __STATS(, __stats_readyQ_pop_t & stats)) with (cltr->ready_queue) {
537        // Pick the bet list
538        int w = i;
539        if( __builtin_expect(!is_empty(lanes.data[j]), true) ) {
540                w = (ts(lanes.data[i]) < ts(lanes.data[j])) ? i : j;
541        }
542
543        return try_pop(cltr, w __STATS(, stats));
544}
545
546// Call this function of the intrusive list was moved using memcpy
547// fixes the list so that the pointers back to anchors aren't left dangling
548static inline void fix(__intrusive_lane_t & ll) {
549                        if(is_empty(ll)) {
550                                verify(ll.anchor.next == 0p);
551                                ll.prev = mock_head(ll);
552                        }
553}
554
555static void assign_list(unsigned & value, dlist(processor) & list, unsigned count) {
556        processor * it = &list`first;
557        for(unsigned i = 0; i < count; i++) {
558                /* paranoid */ verifyf( it, "Unexpected null iterator, at index %u of %u\n", i, count);
559                it->rdq.id = value;
560                it->rdq.target = -1u;
561                value += READYQ_SHARD_FACTOR;
562                it = &(*it)`next;
563        }
564}
565
566static void reassign_cltr_id(struct cluster * cltr) {
567        unsigned preferred = 0;
568        assign_list(preferred, cltr->procs.actives, cltr->procs.total - cltr->procs.idle);
569        assign_list(preferred, cltr->procs.idles  , cltr->procs.idle );
570}
571
572static void fix_times( struct cluster * cltr ) with( cltr->ready_queue ) {
573        #if defined(USE_WORK_STEALING)
574                lanes.tscs = alloc(lanes.count, lanes.tscs`realloc);
575                for(i; lanes.count) {
576                        unsigned long long tsc = ts(lanes.data[i]);
577                        lanes.tscs[i].tv = tsc != 0 ? tsc : rdtscl();
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, true);
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}
706
707#if !defined(__CFA_NO_STATISTICS__)
708        unsigned cnt(const __ready_queue_t & this, unsigned idx) {
709                /* paranoid */ verify(this.lanes.count > idx);
710                return this.lanes.data[idx].cnt;
711        }
712#endif
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