source: libcfa/src/concurrency/ready_queue.cfa @ 7a2972b

arm-ehjacob/cs343-translationnew-ast-unique-expr
Last change on this file since 7a2972b was 7a2972b, checked in by Thierry Delisle <tdelisle@…>, 7 months ago

ready queue can now toggle between

  • lock-based queue
  • mpsc_queue a.k.a. nemesis queue

slightly messy implementation, some clean up needed.

  • Property mode set to 100644
File size: 18.8 KB
RevLine 
[7768b8d]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__
[1b143de]17// #define __CFA_DEBUG_PRINT_READY_QUEUE__
[7768b8d]18
[1eb239e4]19// #define USE_SNZI
[7a2972b]20// #define USE_MPSC
[1eb239e4]21
[7768b8d]22#include "bits/defs.hfa"
23#include "kernel_private.hfa"
24
25#define _GNU_SOURCE
26#include "stdlib.hfa"
[61d7bec]27#include "math.hfa"
[7768b8d]28
[04b5cef]29#include <unistd.h>
30
[13c5e19]31#include "snzi.hfa"
32#include "ready_subqueue.hfa"
33
[7768b8d]34static const size_t cache_line_size = 64;
35
[dca5802]36// No overriden function, no environment variable, no define
37// fall back to a magic number
38#ifndef __CFA_MAX_PROCESSORS__
[b388ee8]39        #define __CFA_MAX_PROCESSORS__ 1024
[dca5802]40#endif
[7768b8d]41
[3143f28]42#define BIAS 4
[04b5cef]43
[dca5802]44// returns the maximum number of processors the RWLock support
[7768b8d]45__attribute__((weak)) unsigned __max_processors() {
46        const char * max_cores_s = getenv("CFA_MAX_PROCESSORS");
47        if(!max_cores_s) {
[504a7dc]48                __cfadbg_print_nolock(ready_queue, "No CFA_MAX_PROCESSORS in ENV\n");
[dca5802]49                return __CFA_MAX_PROCESSORS__;
[7768b8d]50        }
51
52        char * endptr = 0p;
53        long int max_cores_l = strtol(max_cores_s, &endptr, 10);
54        if(max_cores_l < 1 || max_cores_l > 65535) {
[504a7dc]55                __cfadbg_print_nolock(ready_queue, "CFA_MAX_PROCESSORS out of range : %ld\n", max_cores_l);
[dca5802]56                return __CFA_MAX_PROCESSORS__;
[7768b8d]57        }
58        if('\0' != *endptr) {
[504a7dc]59                __cfadbg_print_nolock(ready_queue, "CFA_MAX_PROCESSORS not a decimal number : %s\n", max_cores_s);
[dca5802]60                return __CFA_MAX_PROCESSORS__;
[7768b8d]61        }
62
63        return max_cores_l;
64}
65
66//=======================================================================
67// Cluster wide reader-writer lock
68//=======================================================================
[b388ee8]69void  ?{}(__scheduler_RWLock_t & this) {
[7768b8d]70        this.max   = __max_processors();
71        this.alloc = 0;
72        this.ready = 0;
73        this.lock  = false;
74        this.data  = alloc(this.max);
75
76        /*paranoid*/ verify( 0 == (((uintptr_t)(this.data    )) % 64) );
77        /*paranoid*/ verify( 0 == (((uintptr_t)(this.data + 1)) % 64) );
78        /*paranoid*/ verify(__atomic_is_lock_free(sizeof(this.alloc), &this.alloc));
79        /*paranoid*/ verify(__atomic_is_lock_free(sizeof(this.ready), &this.ready));
80
81}
[b388ee8]82void ^?{}(__scheduler_RWLock_t & this) {
[7768b8d]83        free(this.data);
84}
85
[9b1dcc2]86void ?{}( __scheduler_lock_id_t & this, __processor_id_t * proc ) {
[7768b8d]87        this.handle = proc;
88        this.lock   = false;
[64a7146]89        #ifdef __CFA_WITH_VERIFY__
90                this.owned  = false;
91        #endif
[7768b8d]92}
93
94//=======================================================================
95// Lock-Free registering/unregistering of threads
[9b1dcc2]96unsigned doregister( struct __processor_id_t * proc ) with(*__scheduler_lock) {
[b388ee8]97        __cfadbg_print_safe(ready_queue, "Kernel : Registering proc %p for RW-Lock\n", proc);
[504a7dc]98
[7768b8d]99        // Step - 1 : check if there is already space in the data
100        uint_fast32_t s = ready;
101
102        // Check among all the ready
103        for(uint_fast32_t i = 0; i < s; i++) {
[9b1dcc2]104                __processor_id_t * null = 0p; // Re-write every loop since compare thrashes it
[7768b8d]105                if( __atomic_load_n(&data[i].handle, (int)__ATOMIC_RELAXED) == null
106                        && __atomic_compare_exchange_n( &data[i].handle, &null, proc, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
107                        /*paranoid*/ verify(i < ready);
[64a7146]108                        /*paranoid*/ verify(0 == (__alignof__(data[i]) % cache_line_size));
[7768b8d]109                        /*paranoid*/ verify((((uintptr_t)&data[i]) % cache_line_size) == 0);
110                        return i;
111                }
112        }
113
[b388ee8]114        if(max <= alloc) abort("Trying to create more than %ud processors", __scheduler_lock->max);
[7768b8d]115
116        // Step - 2 : F&A to get a new spot in the array.
117        uint_fast32_t n = __atomic_fetch_add(&alloc, 1, __ATOMIC_SEQ_CST);
[b388ee8]118        if(max <= n) abort("Trying to create more than %ud processors", __scheduler_lock->max);
[7768b8d]119
120        // Step - 3 : Mark space as used and then publish it.
[9b1dcc2]121        __scheduler_lock_id_t * storage = (__scheduler_lock_id_t *)&data[n];
[7768b8d]122        (*storage){ proc };
[fd9b524]123        while() {
[7768b8d]124                unsigned copy = n;
125                if( __atomic_load_n(&ready, __ATOMIC_RELAXED) == n
126                        && __atomic_compare_exchange_n(&ready, &copy, n + 1, true, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST))
127                        break;
[fd9b524]128                Pause();
[7768b8d]129        }
130
[1b143de]131        __cfadbg_print_safe(ready_queue, "Kernel : Registering proc %p done, id %lu\n", proc, n);
[504a7dc]132
[7768b8d]133        // Return new spot.
134        /*paranoid*/ verify(n < ready);
[37ba662]135        /*paranoid*/ verify(__alignof__(data[n]) == (2 * cache_line_size));
[7768b8d]136        /*paranoid*/ verify((((uintptr_t)&data[n]) % cache_line_size) == 0);
137        return n;
138}
139
[9b1dcc2]140void unregister( struct __processor_id_t * proc ) with(*__scheduler_lock) {
[7768b8d]141        unsigned id = proc->id;
142        /*paranoid*/ verify(id < ready);
143        /*paranoid*/ verify(proc == __atomic_load_n(&data[id].handle, __ATOMIC_RELAXED));
144        __atomic_store_n(&data[id].handle, 0p, __ATOMIC_RELEASE);
[504a7dc]145
146        __cfadbg_print_safe(ready_queue, "Kernel : Unregister proc %p\n", proc);
[7768b8d]147}
148
149//-----------------------------------------------------------------------
150// Writer side : acquire when changing the ready queue, e.g. adding more
151//  queues or removing them.
[b388ee8]152uint_fast32_t ready_mutate_lock( void ) with(*__scheduler_lock) {
[8fc652e0]153        /* paranoid */ verify( ! __preemption_enabled() );
[62502cc4]154
[7768b8d]155        // Step 1 : lock global lock
156        // It is needed to avoid processors that register mid Critical-Section
157        //   to simply lock their own lock and enter.
158        __atomic_acquire( &lock );
159
160        // Step 2 : lock per-proc lock
161        // Processors that are currently being registered aren't counted
162        //   but can't be in read_lock or in the critical section.
163        // All other processors are counted
164        uint_fast32_t s = ready;
165        for(uint_fast32_t i = 0; i < s; i++) {
166                __atomic_acquire( &data[i].lock );
167        }
168
[8fc652e0]169        /* paranoid */ verify( ! __preemption_enabled() );
[7768b8d]170        return s;
171}
172
[b388ee8]173void ready_mutate_unlock( uint_fast32_t last_s ) with(*__scheduler_lock) {
[8fc652e0]174        /* paranoid */ verify( ! __preemption_enabled() );
[62502cc4]175
[7768b8d]176        // Step 1 : release local locks
177        // This must be done while the global lock is held to avoid
178        //   threads that where created mid critical section
179        //   to race to lock their local locks and have the writer
180        //   immidiately unlock them
181        // Alternative solution : return s in write_lock and pass it to write_unlock
182        for(uint_fast32_t i = 0; i < last_s; i++) {
183                verify(data[i].lock);
184                __atomic_store_n(&data[i].lock, (bool)false, __ATOMIC_RELEASE);
185        }
186
187        // Step 2 : release global lock
188        /*paranoid*/ assert(true == lock);
189        __atomic_store_n(&lock, (bool)false, __ATOMIC_RELEASE);
[62502cc4]190
[8fc652e0]191        /* paranoid */ verify( ! __preemption_enabled() );
[7768b8d]192}
193
194//=======================================================================
[13c5e19]195// Cforall Reqdy Queue used for scheduling
[b798713]196//=======================================================================
197void ?{}(__ready_queue_t & this) with (this) {
[28d73c1]198        lanes.data  = 0p;
199        lanes.count = 0;
[b798713]200}
201
202void ^?{}(__ready_queue_t & this) with (this) {
[39fc03e]203        verify( 1 == lanes.count );
[1eb239e4]204        #ifdef USE_SNZI
205                verify( !query( snzi ) );
206        #endif
[dca5802]207        free(lanes.data);
208}
209
[64a7146]210//-----------------------------------------------------------------------
211__attribute__((hot)) bool query(struct cluster * cltr) {
[1eb239e4]212        #ifdef USE_SNZI
213                return query(cltr->ready_queue.snzi);
214        #endif
215        return true;
[64a7146]216}
217
[772411a]218static inline [unsigned, bool] idx_from_r(unsigned r, unsigned preferred) {
219        unsigned i;
220        bool local;
221        #if defined(BIAS)
222                unsigned rlow  = r % BIAS;
223                unsigned rhigh = r / BIAS;
224                if((0 != rlow) && preferred >= 0) {
225                        // (BIAS - 1) out of BIAS chances
226                        // Use perferred queues
227                        i = preferred + (rhigh % 4);
228                        local = true;
229                }
230                else {
231                        // 1 out of BIAS chances
232                        // Use all queues
233                        i = rhigh;
234                        local = false;
235                }
236        #else
237                i = r;
238                local = false;
239        #endif
240        return [i, local];
241}
242
[dca5802]243//-----------------------------------------------------------------------
[504a7dc]244__attribute__((hot)) bool push(struct cluster * cltr, struct $thread * thrd) with (cltr->ready_queue) {
[61d7bec]245        __cfadbg_print_safe(ready_queue, "Kernel : Pushing %p on cluster %p\n", thrd, cltr);
[1b143de]246
[fd1f65e]247        #if !defined(__CFA_NO_STATISTICS__)
[a344425]248                const bool external = (!kernelTLS().this_proc_id->full_proc) || (cltr != kernelTLS().this_processor->cltr);
[fd1f65e]249        #endif
250
[dca5802]251        // write timestamp
[b798713]252        thrd->link.ts = rdtscl();
253
[c426b03]254        bool first = false;
[772411a]255        __attribute__((unused)) bool local;
256        __attribute__((unused)) int preferred;
257        #if defined(BIAS)
258                preferred =
[d72c074]259                        //*
[bd0bdd37]260                        kernelTLS().this_processor ? kernelTLS().this_processor->cltr_id : -1;
[d72c074]261                        /*/
262                        thrd->link.preferred * 4;
263                        //*/
[52769ba]264        #endif
265
[dca5802]266        // Try to pick a lane and lock it
267        unsigned i;
268        do {
269                // Pick the index of a lane
[5fe7322]270                // unsigned r = __tls_rand();
271                unsigned r = __tls_rand_fwd();
[772411a]272                [i, local] = idx_from_r(r, preferred);
273
[04b5cef]274                i %= __atomic_load_n( &lanes.count, __ATOMIC_RELAXED );
[b798713]275
276                #if !defined(__CFA_NO_STATISTICS__)
[fd1f65e]277                        if(external) {
278                                if(local) __atomic_fetch_add(&cltr->stats->ready.pick.ext.local, 1, __ATOMIC_RELAXED);
279                                __atomic_fetch_add(&cltr->stats->ready.pick.ext.attempt, 1, __ATOMIC_RELAXED);
280                        }
281                        else {
282                                if(local) __tls_stats()->ready.pick.push.local++;
283                                __tls_stats()->ready.pick.push.attempt++;
284                        }
[b798713]285                #endif
286
[7a2972b]287        #if defined(USE_MPSC)
288                // mpsc always succeeds
289        } while( false );
290        #else
[b798713]291                // If we can't lock it retry
[dca5802]292        } while( !__atomic_try_acquire( &lanes.data[i].lock ) );
[7a2972b]293        #endif
[b798713]294
[dca5802]295        // Actually push it
[5fe7322]296        #ifdef USE_SNZI
297                bool lane_first =
298        #endif
299
300        push(lanes.data[i], thrd);
[dca5802]301
[1eb239e4]302        #ifdef USE_SNZI
303                // If this lane used to be empty we need to do more
304                if(lane_first) {
305                        // Check if the entire queue used to be empty
306                        first = !query(snzi);
[61d7bec]307
[1eb239e4]308                        // Update the snzi
309                        arrive( snzi, i );
310                }
311        #endif
[dca5802]312
[7a2972b]313        #if !defined(USE_MPSC)
314                // Unlock and return
315                __atomic_unlock( &lanes.data[i].lock );
316        #endif
[dca5802]317
[c426b03]318        // Mark the current index in the tls rng instance as having an item
319        __tls_rand_advance_bck();
320
[1b143de]321        __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);
322
[dca5802]323        // Update statistics
324        #if !defined(__CFA_NO_STATISTICS__)
[fd1f65e]325                if(external) {
326                        if(local) __atomic_fetch_add(&cltr->stats->ready.pick.ext.lsuccess, 1, __ATOMIC_RELAXED);
327                        __atomic_fetch_add(&cltr->stats->ready.pick.ext.success, 1, __ATOMIC_RELAXED);
328                }
329                else {
330                        if(local) __tls_stats()->ready.pick.push.lsuccess++;
331                        __tls_stats()->ready.pick.push.success++;
332                }
[dca5802]333        #endif
334
335        // return whether or not the list was empty before this push
336        return first;
[b798713]337}
338
[13c5e19]339static struct $thread * try_pop(struct cluster * cltr, unsigned i, unsigned j);
340static struct $thread * try_pop(struct cluster * cltr, unsigned i);
341
342// Pop from the ready queue from a given cluster
343__attribute__((hot)) $thread * pop(struct cluster * cltr) with (cltr->ready_queue) {
344        /* paranoid */ verify( lanes.count > 0 );
[1eb239e4]345        unsigned count = __atomic_load_n( &lanes.count, __ATOMIC_RELAXED );
[772411a]346        int preferred;
[13c5e19]347        #if defined(BIAS)
348                // Don't bother trying locally too much
[bd0bdd37]349                preferred = kernelTLS().this_processor->cltr_id;
[13c5e19]350        #endif
351
[772411a]352
[13c5e19]353        // As long as the list is not empty, try finding a lane that isn't empty and pop from it
[1eb239e4]354        #ifdef USE_SNZI
355                while( query(snzi) ) {
356        #else
357                for(25) {
358        #endif
[13c5e19]359                // Pick two lists at random
[5fe7322]360                // unsigned ri = __tls_rand();
361                // unsigned rj = __tls_rand();
362                unsigned ri = __tls_rand_bck();
363                unsigned rj = __tls_rand_bck();
[772411a]364
365                unsigned i, j;
366                __attribute__((unused)) bool locali, localj;
367                [i, locali] = idx_from_r(ri, preferred);
368                [j, localj] = idx_from_r(rj, preferred);
369
370                #if !defined(__CFA_NO_STATISTICS__)
[3143f28]371                        if(locali && localj) {
[772411a]372                                __tls_stats()->ready.pick.pop.local++;
[13c5e19]373                        }
374                #endif
375
[1eb239e4]376                i %= count;
377                j %= count;
[13c5e19]378
379                // try popping from the 2 picked lists
380                struct $thread * thrd = try_pop(cltr, i, j);
[52769ba]381                if(thrd) {
382                        #if defined(BIAS) && !defined(__CFA_NO_STATISTICS__)
[772411a]383                                if( locali || localj ) __tls_stats()->ready.pick.pop.lsuccess++;
[52769ba]384                        #endif
385                        return thrd;
386                }
[13c5e19]387        }
388
389        // All lanes where empty return 0p
390        return 0p;
391}
392
[1eb239e4]393__attribute__((hot)) struct $thread * pop_slow(struct cluster * cltr) with (cltr->ready_queue) {
394        /* paranoid */ verify( lanes.count > 0 );
395        unsigned count = __atomic_load_n( &lanes.count, __ATOMIC_RELAXED );
396        unsigned offset = __tls_rand();
397        for(i; count) {
398                unsigned idx = (offset + i) % count;
399                struct $thread * thrd = try_pop(cltr, idx);
400                if(thrd) {
401                        return thrd;
402                }
403        }
404
405        // All lanes where empty return 0p
406        return 0p;
407}
408
409
[b798713]410//-----------------------------------------------------------------------
[dca5802]411// Given 2 indexes, pick the list with the oldest push an try to pop from it
[13c5e19]412static inline struct $thread * try_pop(struct cluster * cltr, unsigned i, unsigned j) with (cltr->ready_queue) {
[b798713]413        #if !defined(__CFA_NO_STATISTICS__)
[8834751]414                __tls_stats()->ready.pick.pop.attempt++;
[b798713]415        #endif
416
417        // Pick the bet list
418        int w = i;
[dca5802]419        if( __builtin_expect(!is_empty(lanes.data[j]), true) ) {
420                w = (ts(lanes.data[i]) < ts(lanes.data[j])) ? i : j;
[b798713]421        }
422
[13c5e19]423        return try_pop(cltr, w);
424}
425
426static inline struct $thread * try_pop(struct cluster * cltr, unsigned w) with (cltr->ready_queue) {
[dca5802]427        // Get relevant elements locally
428        __intrusive_lane_t & lane = lanes.data[w];
429
[b798713]430        // If list looks empty retry
[dca5802]431        if( is_empty(lane) ) return 0p;
[b798713]432
433        // If we can't get the lock retry
[dca5802]434        if( !__atomic_try_acquire(&lane.lock) ) return 0p;
[b798713]435
436
437        // If list is empty, unlock and retry
[dca5802]438        if( is_empty(lane) ) {
439                __atomic_unlock(&lane.lock);
[b798713]440                return 0p;
441        }
442
443        // Actually pop the list
[504a7dc]444        struct $thread * thrd;
[343d10e]445        thrd = pop(lane);
[b798713]446
[dca5802]447        /* paranoid */ verify(thrd);
448        /* paranoid */ verify(lane.lock);
[b798713]449
[1eb239e4]450        #ifdef USE_SNZI
451                // If this was the last element in the lane
452                if(emptied) {
453                        depart( snzi, w );
454                }
455        #endif
[b798713]456
457        // Unlock and return
[dca5802]458        __atomic_unlock(&lane.lock);
[b798713]459
[dca5802]460        // Update statistics
[b798713]461        #if !defined(__CFA_NO_STATISTICS__)
[8834751]462                __tls_stats()->ready.pick.pop.success++;
[b798713]463        #endif
464
[d72c074]465        // Update the thread bias
466        thrd->link.preferred = w / 4;
467
[dca5802]468        // return the popped thread
[b798713]469        return thrd;
470}
[13c5e19]471//-----------------------------------------------------------------------
[b798713]472
[13c5e19]473bool remove_head(struct cluster * cltr, struct $thread * thrd) with (cltr->ready_queue) {
474        for(i; lanes.count) {
475                __intrusive_lane_t & lane = lanes.data[i];
[b798713]476
[13c5e19]477                bool removed = false;
[04b5cef]478
[13c5e19]479                __atomic_acquire(&lane.lock);
480                        if(head(lane)->link.next == thrd) {
481                                $thread * pthrd;
[343d10e]482                                pthrd = pop(lane);
[04b5cef]483
[13c5e19]484                                /* paranoid */ verify( pthrd == thrd );
[61d7bec]485
[13c5e19]486                                removed = true;
[1eb239e4]487                                #ifdef USE_SNZI
488                                        if(emptied) {
489                                                depart( snzi, i );
490                                        }
491                                #endif
[13c5e19]492                        }
493                __atomic_unlock(&lane.lock);
[b798713]494
[13c5e19]495                if( removed ) return true;
496        }
497        return false;
[b798713]498}
499
500//-----------------------------------------------------------------------
501
502static void check( __ready_queue_t & q ) with (q) {
[7a2972b]503        #if defined(__CFA_WITH_VERIFY__) && !defined(USE_MPSC)
[b798713]504                {
[dca5802]505                        for( idx ; lanes.count ) {
506                                __intrusive_lane_t & sl = lanes.data[idx];
507                                assert(!lanes.data[idx].lock);
[b798713]508
509                                assert(head(sl)->link.prev == 0p );
510                                assert(head(sl)->link.next->link.prev == head(sl) );
511                                assert(tail(sl)->link.next == 0p );
512                                assert(tail(sl)->link.prev->link.next == tail(sl) );
513
[7a2972b]514                                if(is_empty(sl)) {
[b798713]515                                        assert(tail(sl)->link.prev == head(sl));
516                                        assert(head(sl)->link.next == tail(sl));
[1b143de]517                                } else {
518                                        assert(tail(sl)->link.prev != head(sl));
519                                        assert(head(sl)->link.next != tail(sl));
[b798713]520                                }
521                        }
522                }
523        #endif
524}
525
526// Call this function of the intrusive list was moved using memcpy
[dca5802]527// fixes the list so that the pointers back to anchors aren't left dangling
528static inline void fix(__intrusive_lane_t & ll) {
[7a2972b]529        #if !defined(USE_MPSC)
530                // if the list is not empty then follow he pointer and fix its reverse
531                if(!is_empty(ll)) {
532                        head(ll)->link.next->link.prev = head(ll);
533                        tail(ll)->link.prev->link.next = tail(ll);
534                }
535                // Otherwise just reset the list
536                else {
537                        verify(tail(ll)->link.next == 0p);
538                        tail(ll)->link.prev = head(ll);
539                        head(ll)->link.next = tail(ll);
540                        verify(head(ll)->link.prev == 0p);
541                }
542        #endif
[b798713]543}
544
[dca5802]545// Grow the ready queue
[bd0bdd37]546unsigned ready_queue_grow(struct cluster * cltr, int target) {
547        unsigned preferred;
548        size_t ncount;
549
[64a7146]550        /* paranoid */ verify( ready_mutate_islocked() );
[504a7dc]551        __cfadbg_print_safe(ready_queue, "Kernel : Growing ready queue\n");
[b798713]552
[dca5802]553        // Make sure that everything is consistent
554        /* paranoid */ check( cltr->ready_queue );
555
556        // grow the ready queue
[b798713]557        with( cltr->ready_queue ) {
[1eb239e4]558                #ifdef USE_SNZI
559                        ^(snzi){};
560                #endif
[b798713]561
[39fc03e]562                // Find new count
563                // Make sure we always have atleast 1 list
[bd0bdd37]564                if(target >= 2) {
565                        ncount = target * 4;
566                        preferred = ncount - 4;
567                } else {
568                        ncount = 1;
569                        preferred = 0;
570                }
[b798713]571
[dca5802]572                // Allocate new array (uses realloc and memcpies the data)
[ceb7db8]573                lanes.data = alloc( ncount, lanes.data`realloc );
[b798713]574
575                // Fix the moved data
[dca5802]576                for( idx; (size_t)lanes.count ) {
577                        fix(lanes.data[idx]);
[b798713]578                }
579
580                // Construct new data
[dca5802]581                for( idx; (size_t)lanes.count ~ ncount) {
582                        (lanes.data[idx]){};
[b798713]583                }
584
585                // Update original
[dca5802]586                lanes.count = ncount;
587
[1eb239e4]588                #ifdef USE_SNZI
589                        // Re-create the snzi
590                        snzi{ log2( lanes.count / 8 ) };
591                        for( idx; (size_t)lanes.count ) {
592                                if( !is_empty(lanes.data[idx]) ) {
593                                        arrive(snzi, idx);
594                                }
[61d7bec]595                        }
[1eb239e4]596                #endif
[b798713]597        }
598
599        // Make sure that everything is consistent
[dca5802]600        /* paranoid */ check( cltr->ready_queue );
601
[504a7dc]602        __cfadbg_print_safe(ready_queue, "Kernel : Growing ready queue done\n");
[dca5802]603
[64a7146]604        /* paranoid */ verify( ready_mutate_islocked() );
[bd0bdd37]605        return preferred;
[b798713]606}
607
[dca5802]608// Shrink the ready queue
[320ec6fc]609void ready_queue_shrink(struct cluster * cltr, int target) {
[64a7146]610        /* paranoid */ verify( ready_mutate_islocked() );
[504a7dc]611        __cfadbg_print_safe(ready_queue, "Kernel : Shrinking ready queue\n");
[dca5802]612
613        // Make sure that everything is consistent
614        /* paranoid */ check( cltr->ready_queue );
615
[b798713]616        with( cltr->ready_queue ) {
[1eb239e4]617                #ifdef USE_SNZI
618                        ^(snzi){};
619                #endif
[61d7bec]620
[39fc03e]621                // Remember old count
[dca5802]622                size_t ocount = lanes.count;
[b798713]623
[39fc03e]624                // Find new count
625                // Make sure we always have atleast 1 list
626                lanes.count = target >= 2 ? target * 4: 1;
627                /* paranoid */ verify( ocount >= lanes.count );
[320ec6fc]628                /* paranoid */ verify( lanes.count == target * 4 || target < 2 );
[dca5802]629
630                // for printing count the number of displaced threads
[504a7dc]631                #if defined(__CFA_DEBUG_PRINT__) || defined(__CFA_DEBUG_PRINT_READY_QUEUE__)
[dca5802]632                        __attribute__((unused)) size_t displaced = 0;
633                #endif
[b798713]634
635                // redistribute old data
[dca5802]636                for( idx; (size_t)lanes.count ~ ocount) {
637                        // Lock is not strictly needed but makes checking invariants much easier
[1b143de]638                        __attribute__((unused)) bool locked = __atomic_try_acquire(&lanes.data[idx].lock);
[b798713]639                        verify(locked);
[dca5802]640
641                        // As long as we can pop from this lane to push the threads somewhere else in the queue
642                        while(!is_empty(lanes.data[idx])) {
[504a7dc]643                                struct $thread * thrd;
[343d10e]644                                thrd = pop(lanes.data[idx]);
[dca5802]645
[b798713]646                                push(cltr, thrd);
[dca5802]647
648                                // for printing count the number of displaced threads
[504a7dc]649                                #if defined(__CFA_DEBUG_PRINT__) || defined(__CFA_DEBUG_PRINT_READY_QUEUE__)
[dca5802]650                                        displaced++;
651                                #endif
[b798713]652                        }
653
[dca5802]654                        // Unlock the lane
655                        __atomic_unlock(&lanes.data[idx].lock);
[b798713]656
657                        // TODO print the queue statistics here
658
[dca5802]659                        ^(lanes.data[idx]){};
[b798713]660                }
661
[504a7dc]662                __cfadbg_print_safe(ready_queue, "Kernel : Shrinking ready queue displaced %zu threads\n", displaced);
[c84b4be]663
[dca5802]664                // Allocate new array (uses realloc and memcpies the data)
[ceb7db8]665                lanes.data = alloc( lanes.count, lanes.data`realloc );
[b798713]666
667                // Fix the moved data
[dca5802]668                for( idx; (size_t)lanes.count ) {
669                        fix(lanes.data[idx]);
[b798713]670                }
[c84b4be]671
[1eb239e4]672                #ifdef USE_SNZI
673                        // Re-create the snzi
674                        snzi{ log2( lanes.count / 8 ) };
675                        for( idx; (size_t)lanes.count ) {
676                                if( !is_empty(lanes.data[idx]) ) {
677                                        arrive(snzi, idx);
678                                }
[61d7bec]679                        }
[1eb239e4]680                #endif
[b798713]681        }
682
683        // Make sure that everything is consistent
[dca5802]684        /* paranoid */ check( cltr->ready_queue );
685
[504a7dc]686        __cfadbg_print_safe(ready_queue, "Kernel : Shrinking ready queue done\n");
[64a7146]687        /* paranoid */ verify( ready_mutate_islocked() );
[fd9b524]688}
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