source: libcfa/src/concurrency/ready_queue.cfa@ 49b3389

ADT ast-experimental enum forall-pointer-decay pthread-emulation qualifiedEnum
Last change on this file since 49b3389 was c86ee4c, checked in by Thierry Delisle <tdelisle@…>, 4 years ago

Merge branch 'master' of plg.uwaterloo.ca:software/cfa/cfa-cc
  • Property mode set to 100644
File size: 31.1 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// #define USE_CPU_WORK_STEALING
25
26#include "bits/defs.hfa"
27#include "device/cpu.hfa"
28#include "kernel_private.hfa"
29
30#include "stdlib.hfa"
31#include "math.hfa"
32
33#include <errno.h>
34#include <unistd.h>
35
36extern "C" {
37 #include <sys/syscall.h> // __NR_xxx
38}
39
40#include "ready_subqueue.hfa"
41
42static const size_t cache_line_size = 64;
43
44#if !defined(__CFA_NO_STATISTICS__)
45 #define __STATS(...) __VA_ARGS__
46#else
47 #define __STATS(...)
48#endif
49
50// No overriden function, no environment variable, no define
51// fall back to a magic number
52#ifndef __CFA_MAX_PROCESSORS__
53 #define __CFA_MAX_PROCESSORS__ 1024
54#endif
55
56#if defined(USE_CPU_WORK_STEALING)
57 #define READYQ_SHARD_FACTOR 2
58#elif defined(USE_RELAXED_FIFO)
59 #define BIAS 4
60 #define READYQ_SHARD_FACTOR 4
61 #define SEQUENTIAL_SHARD 1
62#elif defined(USE_WORK_STEALING)
63 #define READYQ_SHARD_FACTOR 2
64 #define SEQUENTIAL_SHARD 2
65#else
66 #error no scheduling strategy selected
67#endif
68
69static inline struct thread$ * try_pop(struct cluster * cltr, unsigned w __STATS(, __stats_readyQ_pop_t & stats));
70static inline struct thread$ * try_pop(struct cluster * cltr, unsigned i, unsigned j __STATS(, __stats_readyQ_pop_t & stats));
71static inline struct thread$ * search(struct cluster * cltr);
72static inline [unsigned, bool] idx_from_r(unsigned r, unsigned preferred);
73
74
75// returns the maximum number of processors the RWLock support
76__attribute__((weak)) unsigned __max_processors() {
77 const char * max_cores_s = getenv("CFA_MAX_PROCESSORS");
78 if(!max_cores_s) {
79 __cfadbg_print_nolock(ready_queue, "No CFA_MAX_PROCESSORS in ENV\n");
80 return __CFA_MAX_PROCESSORS__;
81 }
82
83 char * endptr = 0p;
84 long int max_cores_l = strtol(max_cores_s, &endptr, 10);
85 if(max_cores_l < 1 || max_cores_l > 65535) {
86 __cfadbg_print_nolock(ready_queue, "CFA_MAX_PROCESSORS out of range : %ld\n", max_cores_l);
87 return __CFA_MAX_PROCESSORS__;
88 }
89 if('\0' != *endptr) {
90 __cfadbg_print_nolock(ready_queue, "CFA_MAX_PROCESSORS not a decimal number : %s\n", max_cores_s);
91 return __CFA_MAX_PROCESSORS__;
92 }
93
94 return max_cores_l;
95}
96
97#if defined(CFA_HAVE_LINUX_LIBRSEQ)
98 // No forward declaration needed
99 #define __kernel_rseq_register rseq_register_current_thread
100 #define __kernel_rseq_unregister rseq_unregister_current_thread
101#elif defined(CFA_HAVE_LINUX_RSEQ_H)
102 void __kernel_raw_rseq_register (void);
103 void __kernel_raw_rseq_unregister(void);
104
105 #define __kernel_rseq_register __kernel_raw_rseq_register
106 #define __kernel_rseq_unregister __kernel_raw_rseq_unregister
107#else
108 // No forward declaration needed
109 // No initialization needed
110 static inline void noop(void) {}
111
112 #define __kernel_rseq_register noop
113 #define __kernel_rseq_unregister noop
114#endif
115
116//=======================================================================
117// Cluster wide reader-writer lock
118//=======================================================================
119void ?{}(__scheduler_RWLock_t & this) {
120 this.max = __max_processors();
121 this.alloc = 0;
122 this.ready = 0;
123 this.data = alloc(this.max);
124 this.write_lock = false;
125
126 /*paranoid*/ verify(__atomic_is_lock_free(sizeof(this.alloc), &this.alloc));
127 /*paranoid*/ verify(__atomic_is_lock_free(sizeof(this.ready), &this.ready));
128
129}
130void ^?{}(__scheduler_RWLock_t & this) {
131 free(this.data);
132}
133
134
135//=======================================================================
136// Lock-Free registering/unregistering of threads
137unsigned register_proc_id( void ) with(*__scheduler_lock) {
138 __kernel_rseq_register();
139
140 __cfadbg_print_safe(ready_queue, "Kernel : Registering proc %p for RW-Lock\n", proc);
141 bool * handle = (bool *)&kernelTLS().sched_lock;
142
143 // Step - 1 : check if there is already space in the data
144 uint_fast32_t s = ready;
145
146 // Check among all the ready
147 for(uint_fast32_t i = 0; i < s; i++) {
148 bool * volatile * cell = (bool * volatile *)&data[i]; // Cforall is bugged and the double volatiles causes problems
149 /* paranoid */ verify( handle != *cell );
150
151 bool * null = 0p; // Re-write every loop since compare thrashes it
152 if( __atomic_load_n(cell, (int)__ATOMIC_RELAXED) == null
153 && __atomic_compare_exchange_n( cell, &null, handle, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
154 /* paranoid */ verify(i < ready);
155 /* paranoid */ verify( (kernelTLS().sched_id = i, true) );
156 return i;
157 }
158 }
159
160 if(max <= alloc) abort("Trying to create more than %ud processors", __scheduler_lock->max);
161
162 // Step - 2 : F&A to get a new spot in the array.
163 uint_fast32_t n = __atomic_fetch_add(&alloc, 1, __ATOMIC_SEQ_CST);
164 if(max <= n) abort("Trying to create more than %ud processors", __scheduler_lock->max);
165
166 // Step - 3 : Mark space as used and then publish it.
167 data[n] = handle;
168 while() {
169 unsigned copy = n;
170 if( __atomic_load_n(&ready, __ATOMIC_RELAXED) == n
171 && __atomic_compare_exchange_n(&ready, &copy, n + 1, true, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST))
172 break;
173 Pause();
174 }
175
176 __cfadbg_print_safe(ready_queue, "Kernel : Registering proc %p done, id %lu\n", proc, n);
177
178 // Return new spot.
179 /* paranoid */ verify(n < ready);
180 /* paranoid */ verify( (kernelTLS().sched_id = n, true) );
181 return n;
182}
183
184void unregister_proc_id( unsigned id ) with(*__scheduler_lock) {
185 /* paranoid */ verify(id < ready);
186 /* paranoid */ verify(id == kernelTLS().sched_id);
187 /* paranoid */ verify(data[id] == &kernelTLS().sched_lock);
188
189 bool * volatile * cell = (bool * volatile *)&data[id]; // Cforall is bugged and the double volatiles causes problems
190
191 __atomic_store_n(cell, 0p, __ATOMIC_RELEASE);
192
193 __cfadbg_print_safe(ready_queue, "Kernel : Unregister proc %p\n", proc);
194
195 __kernel_rseq_unregister();
196}
197
198//-----------------------------------------------------------------------
199// Writer side : acquire when changing the ready queue, e.g. adding more
200// queues or removing them.
201uint_fast32_t ready_mutate_lock( void ) with(*__scheduler_lock) {
202 /* paranoid */ verify( ! __preemption_enabled() );
203 /* paranoid */ verify( ! kernelTLS().sched_lock );
204
205 // Step 1 : lock global lock
206 // It is needed to avoid processors that register mid Critical-Section
207 // to simply lock their own lock and enter.
208 __atomic_acquire( &write_lock );
209
210 // Step 2 : lock per-proc lock
211 // Processors that are currently being registered aren't counted
212 // but can't be in read_lock or in the critical section.
213 // All other processors are counted
214 uint_fast32_t s = ready;
215 for(uint_fast32_t i = 0; i < s; i++) {
216 volatile bool * llock = data[i];
217 if(llock) __atomic_acquire( llock );
218 }
219
220 /* paranoid */ verify( ! __preemption_enabled() );
221 return s;
222}
223
224void ready_mutate_unlock( uint_fast32_t last_s ) with(*__scheduler_lock) {
225 /* paranoid */ verify( ! __preemption_enabled() );
226
227 // Step 1 : release local locks
228 // This must be done while the global lock is held to avoid
229 // threads that where created mid critical section
230 // to race to lock their local locks and have the writer
231 // immidiately unlock them
232 // Alternative solution : return s in write_lock and pass it to write_unlock
233 for(uint_fast32_t i = 0; i < last_s; i++) {
234 volatile bool * llock = data[i];
235 if(llock) __atomic_store_n(llock, (bool)false, __ATOMIC_RELEASE);
236 }
237
238 // Step 2 : release global lock
239 /*paranoid*/ assert(true == write_lock);
240 __atomic_store_n(&write_lock, (bool)false, __ATOMIC_RELEASE);
241
242 /* paranoid */ verify( ! __preemption_enabled() );
243}
244
245//=======================================================================
246// Cforall Ready Queue used for scheduling
247//=======================================================================
248void ?{}(__ready_queue_t & this) with (this) {
249 #if defined(USE_CPU_WORK_STEALING)
250 lanes.count = cpu_info.hthrd_count * READYQ_SHARD_FACTOR;
251 lanes.data = alloc( lanes.count );
252 lanes.tscs = alloc( lanes.count );
253
254 for( idx; (size_t)lanes.count ) {
255 (lanes.data[idx]){};
256 lanes.tscs[idx].tv = rdtscl();
257 }
258 #else
259 lanes.data = 0p;
260 lanes.tscs = 0p;
261 lanes.count = 0;
262 #endif
263}
264
265void ^?{}(__ready_queue_t & this) with (this) {
266 #if !defined(USE_CPU_WORK_STEALING)
267 verify( SEQUENTIAL_SHARD == lanes.count );
268 #endif
269
270 free(lanes.data);
271 free(lanes.tscs);
272}
273
274//-----------------------------------------------------------------------
275#if defined(USE_CPU_WORK_STEALING)
276 __attribute__((hot)) void push(struct cluster * cltr, struct thread$ * thrd, bool push_local) with (cltr->ready_queue) {
277 __cfadbg_print_safe(ready_queue, "Kernel : Pushing %p on cluster %p\n", thrd, cltr);
278
279 processor * const proc = kernelTLS().this_processor;
280 const bool external = !push_local || (!proc) || (cltr != proc->cltr);
281
282 const int cpu = __kernel_getcpu();
283 /* paranoid */ verify(cpu >= 0);
284 /* paranoid */ verify(cpu < cpu_info.hthrd_count);
285 /* paranoid */ verify(cpu * READYQ_SHARD_FACTOR < lanes.count);
286
287 const cpu_map_entry_t & map = cpu_info.llc_map[cpu];
288 /* paranoid */ verify(map.start * READYQ_SHARD_FACTOR < lanes.count);
289 /* paranoid */ verify(map.self * READYQ_SHARD_FACTOR < lanes.count);
290 /* paranoid */ verifyf((map.start + map.count) * READYQ_SHARD_FACTOR <= lanes.count, "have %zu lanes but map can go up to %u", lanes.count, (map.start + map.count) * READYQ_SHARD_FACTOR);
291
292 const int start = map.self * READYQ_SHARD_FACTOR;
293 unsigned i;
294 do {
295 unsigned r;
296 if(unlikely(external)) { r = __tls_rand(); }
297 else { r = proc->rdq.its++; }
298 i = start + (r % READYQ_SHARD_FACTOR);
299 // If we can't lock it retry
300 } while( !__atomic_try_acquire( &lanes.data[i].lock ) );
301
302 // Actually push it
303 push(lanes.data[i], thrd);
304
305 // Unlock and return
306 __atomic_unlock( &lanes.data[i].lock );
307
308 #if !defined(__CFA_NO_STATISTICS__)
309 if(unlikely(external)) __atomic_fetch_add(&cltr->stats->ready.push.extrn.success, 1, __ATOMIC_RELAXED);
310 else __tls_stats()->ready.push.local.success++;
311 #endif
312
313 __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);
314
315 }
316
317 // Pop from the ready queue from a given cluster
318 __attribute__((hot)) thread$ * pop_fast(struct cluster * cltr) with (cltr->ready_queue) {
319 /* paranoid */ verify( lanes.count > 0 );
320 /* paranoid */ verify( kernelTLS().this_processor );
321
322 const int cpu = __kernel_getcpu();
323 /* paranoid */ verify(cpu >= 0);
324 /* paranoid */ verify(cpu < cpu_info.hthrd_count);
325 /* paranoid */ verify(cpu * READYQ_SHARD_FACTOR < lanes.count);
326
327 const cpu_map_entry_t & map = cpu_info.llc_map[cpu];
328 /* paranoid */ verify(map.start * READYQ_SHARD_FACTOR < lanes.count);
329 /* paranoid */ verify(map.self * READYQ_SHARD_FACTOR < lanes.count);
330 /* paranoid */ verifyf((map.start + map.count) * READYQ_SHARD_FACTOR <= lanes.count, "have %zu lanes but map can go up to %u", lanes.count, (map.start + map.count) * READYQ_SHARD_FACTOR);
331
332 processor * const proc = kernelTLS().this_processor;
333 const int start = map.self * READYQ_SHARD_FACTOR;
334
335 // Did we already have a help target
336 if(proc->rdq.target == -1u) {
337 // if We don't have a
338 unsigned long long min = ts(lanes.data[start]);
339 for(i; READYQ_SHARD_FACTOR) {
340 unsigned long long tsc = ts(lanes.data[start + i]);
341 if(tsc < min) min = tsc;
342 }
343 proc->rdq.cutoff = min;
344
345 /* paranoid */ verify(lanes.count < 65536); // The following code assumes max 65536 cores.
346 /* paranoid */ verify(map.count < 65536); // The following code assumes max 65536 cores.
347
348 if(0 == (__tls_rand() % 10_000)) {
349 proc->rdq.target = __tls_rand() % lanes.count;
350 } else {
351 unsigned cpu_chaos = map.start + (__tls_rand() % map.count);
352 proc->rdq.target = (cpu_chaos * READYQ_SHARD_FACTOR) + (__tls_rand() % READYQ_SHARD_FACTOR);
353 /* paranoid */ verify(proc->rdq.target >= (map.start * READYQ_SHARD_FACTOR));
354 /* paranoid */ verify(proc->rdq.target < ((map.start + map.count) * READYQ_SHARD_FACTOR));
355 }
356
357 /* paranoid */ verify(proc->rdq.target != -1u);
358 }
359 else {
360 const unsigned long long bias = 0; //2_500_000_000;
361 const unsigned long long cutoff = proc->rdq.cutoff > bias ? proc->rdq.cutoff - bias : proc->rdq.cutoff;
362 {
363 unsigned target = proc->rdq.target;
364 proc->rdq.target = -1u;
365 if(lanes.tscs[target].tv < cutoff && ts(lanes.data[target]) < cutoff) {
366 thread$ * t = try_pop(cltr, target __STATS(, __tls_stats()->ready.pop.help));
367 proc->rdq.last = target;
368 if(t) return t;
369 }
370 }
371
372 unsigned last = proc->rdq.last;
373 if(last != -1u && lanes.tscs[last].tv < cutoff && ts(lanes.data[last]) < cutoff) {
374 thread$ * t = try_pop(cltr, last __STATS(, __tls_stats()->ready.pop.help));
375 if(t) return t;
376 }
377 else {
378 proc->rdq.last = -1u;
379 }
380 }
381
382 for(READYQ_SHARD_FACTOR) {
383 unsigned i = start + (proc->rdq.itr++ % READYQ_SHARD_FACTOR);
384 if(thread$ * t = try_pop(cltr, i __STATS(, __tls_stats()->ready.pop.local))) return t;
385 }
386
387 // All lanes where empty return 0p
388 return 0p;
389 }
390
391 __attribute__((hot)) struct thread$ * pop_slow(struct cluster * cltr) with (cltr->ready_queue) {
392 processor * const proc = kernelTLS().this_processor;
393 unsigned last = proc->rdq.last;
394 if(last != -1u) {
395 struct thread$ * t = try_pop(cltr, last __STATS(, __tls_stats()->ready.pop.steal));
396 if(t) return t;
397 proc->rdq.last = -1u;
398 }
399
400 unsigned i = __tls_rand() % lanes.count;
401 return try_pop(cltr, i __STATS(, __tls_stats()->ready.pop.steal));
402 }
403 __attribute__((hot)) struct thread$ * pop_search(struct cluster * cltr) {
404 return search(cltr);
405 }
406#endif
407#if defined(USE_RELAXED_FIFO)
408 //-----------------------------------------------------------------------
409 // get index from random number with or without bias towards queues
410 static inline [unsigned, bool] idx_from_r(unsigned r, unsigned preferred) {
411 unsigned i;
412 bool local;
413 unsigned rlow = r % BIAS;
414 unsigned rhigh = r / BIAS;
415 if((0 != rlow) && preferred >= 0) {
416 // (BIAS - 1) out of BIAS chances
417 // Use perferred queues
418 i = preferred + (rhigh % READYQ_SHARD_FACTOR);
419 local = true;
420 }
421 else {
422 // 1 out of BIAS chances
423 // Use all queues
424 i = rhigh;
425 local = false;
426 }
427 return [i, local];
428 }
429
430 __attribute__((hot)) void push(struct cluster * cltr, struct thread$ * thrd, bool push_local) with (cltr->ready_queue) {
431 __cfadbg_print_safe(ready_queue, "Kernel : Pushing %p on cluster %p\n", thrd, cltr);
432
433 const bool external = !push_local || (!kernelTLS().this_processor) || (cltr != kernelTLS().this_processor->cltr);
434 /* paranoid */ verify(external || kernelTLS().this_processor->rdq.id < lanes.count );
435
436 bool local;
437 int preferred = external ? -1 : kernelTLS().this_processor->rdq.id;
438
439 // Try to pick a lane and lock it
440 unsigned i;
441 do {
442 // Pick the index of a lane
443 unsigned r = __tls_rand_fwd();
444 [i, local] = idx_from_r(r, preferred);
445
446 i %= __atomic_load_n( &lanes.count, __ATOMIC_RELAXED );
447
448 #if !defined(__CFA_NO_STATISTICS__)
449 if(unlikely(external)) __atomic_fetch_add(&cltr->stats->ready.push.extrn.attempt, 1, __ATOMIC_RELAXED);
450 else if(local) __tls_stats()->ready.push.local.attempt++;
451 else __tls_stats()->ready.push.share.attempt++;
452 #endif
453
454 // If we can't lock it retry
455 } while( !__atomic_try_acquire( &lanes.data[i].lock ) );
456
457 // Actually push it
458 push(lanes.data[i], thrd);
459
460 // Unlock and return
461 __atomic_unlock( &lanes.data[i].lock );
462
463 // Mark the current index in the tls rng instance as having an item
464 __tls_rand_advance_bck();
465
466 __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);
467
468 // Update statistics
469 #if !defined(__CFA_NO_STATISTICS__)
470 if(unlikely(external)) __atomic_fetch_add(&cltr->stats->ready.push.extrn.success, 1, __ATOMIC_RELAXED);
471 else if(local) __tls_stats()->ready.push.local.success++;
472 else __tls_stats()->ready.push.share.success++;
473 #endif
474 }
475
476 // Pop from the ready queue from a given cluster
477 __attribute__((hot)) thread$ * pop_fast(struct cluster * cltr) with (cltr->ready_queue) {
478 /* paranoid */ verify( lanes.count > 0 );
479 /* paranoid */ verify( kernelTLS().this_processor );
480 /* paranoid */ verify( kernelTLS().this_processor->rdq.id < lanes.count );
481
482 unsigned count = __atomic_load_n( &lanes.count, __ATOMIC_RELAXED );
483 int preferred = kernelTLS().this_processor->rdq.id;
484
485
486 // As long as the list is not empty, try finding a lane that isn't empty and pop from it
487 for(25) {
488 // Pick two lists at random
489 unsigned ri = __tls_rand_bck();
490 unsigned rj = __tls_rand_bck();
491
492 unsigned i, j;
493 __attribute__((unused)) bool locali, localj;
494 [i, locali] = idx_from_r(ri, preferred);
495 [j, localj] = idx_from_r(rj, preferred);
496
497 i %= count;
498 j %= count;
499
500 // try popping from the 2 picked lists
501 struct thread$ * thrd = try_pop(cltr, i, j __STATS(, *(locali || localj ? &__tls_stats()->ready.pop.local : &__tls_stats()->ready.pop.help)));
502 if(thrd) {
503 return thrd;
504 }
505 }
506
507 // All lanes where empty return 0p
508 return 0p;
509 }
510
511 __attribute__((hot)) struct thread$ * pop_slow(struct cluster * cltr) { return pop_fast(cltr); }
512 __attribute__((hot)) struct thread$ * pop_search(struct cluster * cltr) {
513 return search(cltr);
514 }
515#endif
516#if defined(USE_WORK_STEALING)
517 __attribute__((hot)) void push(struct cluster * cltr, struct thread$ * thrd, bool push_local) with (cltr->ready_queue) {
518 __cfadbg_print_safe(ready_queue, "Kernel : Pushing %p on cluster %p\n", thrd, cltr);
519
520 // #define USE_PREFERRED
521 #if !defined(USE_PREFERRED)
522 const bool external = !push_local || (!kernelTLS().this_processor) || (cltr != kernelTLS().this_processor->cltr);
523 /* paranoid */ verify(external || kernelTLS().this_processor->rdq.id < lanes.count );
524 #else
525 unsigned preferred = thrd->preferred;
526 const bool external = push_local || (!kernelTLS().this_processor) || preferred == -1u || thrd->curr_cluster != cltr;
527 /* paranoid */ verifyf(external || preferred < lanes.count, "Invalid preferred queue %u for %u lanes", preferred, lanes.count );
528
529 unsigned r = preferred % READYQ_SHARD_FACTOR;
530 const unsigned start = preferred - r;
531 #endif
532
533 // Try to pick a lane and lock it
534 unsigned i;
535 do {
536 #if !defined(__CFA_NO_STATISTICS__)
537 if(unlikely(external)) __atomic_fetch_add(&cltr->stats->ready.push.extrn.attempt, 1, __ATOMIC_RELAXED);
538 else __tls_stats()->ready.push.local.attempt++;
539 #endif
540
541 if(unlikely(external)) {
542 i = __tls_rand() % lanes.count;
543 }
544 else {
545 #if !defined(USE_PREFERRED)
546 processor * proc = kernelTLS().this_processor;
547 unsigned r = proc->rdq.its++;
548 i = proc->rdq.id + (r % READYQ_SHARD_FACTOR);
549 #else
550 i = start + (r++ % READYQ_SHARD_FACTOR);
551 #endif
552 }
553 // If we can't lock it retry
554 } while( !__atomic_try_acquire( &lanes.data[i].lock ) );
555
556 // Actually push it
557 push(lanes.data[i], thrd);
558
559 // Unlock and return
560 __atomic_unlock( &lanes.data[i].lock );
561
562 #if !defined(__CFA_NO_STATISTICS__)
563 if(unlikely(external)) __atomic_fetch_add(&cltr->stats->ready.push.extrn.success, 1, __ATOMIC_RELAXED);
564 else __tls_stats()->ready.push.local.success++;
565 #endif
566
567 __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);
568 }
569
570 // Pop from the ready queue from a given cluster
571 __attribute__((hot)) thread$ * pop_fast(struct cluster * cltr) with (cltr->ready_queue) {
572 /* paranoid */ verify( lanes.count > 0 );
573 /* paranoid */ verify( kernelTLS().this_processor );
574 /* paranoid */ verify( kernelTLS().this_processor->rdq.id < lanes.count );
575
576 processor * proc = kernelTLS().this_processor;
577
578 if(proc->rdq.target == -1u) {
579 unsigned long long min = ts(lanes.data[proc->rdq.id]);
580 for(int i = 0; i < READYQ_SHARD_FACTOR; i++) {
581 unsigned long long tsc = ts(lanes.data[proc->rdq.id + i]);
582 if(tsc < min) min = tsc;
583 }
584 proc->rdq.cutoff = min;
585 proc->rdq.target = __tls_rand() % lanes.count;
586 }
587 else {
588 unsigned target = proc->rdq.target;
589 proc->rdq.target = -1u;
590 const unsigned long long bias = 0; //2_500_000_000;
591 const unsigned long long cutoff = proc->rdq.cutoff > bias ? proc->rdq.cutoff - bias : proc->rdq.cutoff;
592 if(lanes.tscs[target].tv < cutoff && ts(lanes.data[target]) < cutoff) {
593 thread$ * t = try_pop(cltr, target __STATS(, __tls_stats()->ready.pop.help));
594 if(t) return t;
595 }
596 }
597
598 for(READYQ_SHARD_FACTOR) {
599 unsigned i = proc->rdq.id + (proc->rdq.itr++ % READYQ_SHARD_FACTOR);
600 if(thread$ * t = try_pop(cltr, i __STATS(, __tls_stats()->ready.pop.local))) return t;
601 }
602 return 0p;
603 }
604
605 __attribute__((hot)) struct thread$ * pop_slow(struct cluster * cltr) with (cltr->ready_queue) {
606 unsigned i = __tls_rand() % lanes.count;
607 return try_pop(cltr, i __STATS(, __tls_stats()->ready.pop.steal));
608 }
609
610 __attribute__((hot)) struct thread$ * pop_search(struct cluster * cltr) with (cltr->ready_queue) {
611 return search(cltr);
612 }
613#endif
614
615//=======================================================================
616// Various Ready Queue utilities
617//=======================================================================
618// these function work the same or almost the same
619// whether they are using work-stealing or relaxed fifo scheduling
620
621//-----------------------------------------------------------------------
622// try to pop from a lane given by index w
623static inline struct thread$ * try_pop(struct cluster * cltr, unsigned w __STATS(, __stats_readyQ_pop_t & stats)) with (cltr->ready_queue) {
624 __STATS( stats.attempt++; )
625
626 // Get relevant elements locally
627 __intrusive_lane_t & lane = lanes.data[w];
628
629 // If list looks empty retry
630 if( is_empty(lane) ) {
631 return 0p;
632 }
633
634 // If we can't get the lock retry
635 if( !__atomic_try_acquire(&lane.lock) ) {
636 return 0p;
637 }
638
639 // If list is empty, unlock and retry
640 if( is_empty(lane) ) {
641 __atomic_unlock(&lane.lock);
642 return 0p;
643 }
644
645 // Actually pop the list
646 struct thread$ * thrd;
647 unsigned long long tsv;
648 [thrd, tsv] = pop(lane);
649
650 /* paranoid */ verify(thrd);
651 /* paranoid */ verify(tsv);
652 /* paranoid */ verify(lane.lock);
653
654 // Unlock and return
655 __atomic_unlock(&lane.lock);
656
657 // Update statistics
658 __STATS( stats.success++; )
659
660 #if defined(USE_WORK_STEALING)
661 lanes.tscs[w].tv = tsv;
662 #endif
663
664 thrd->preferred = w;
665
666 // return the popped thread
667 return thrd;
668}
669
670//-----------------------------------------------------------------------
671// try to pop from any lanes making sure you don't miss any threads push
672// before the start of the function
673static inline struct thread$ * search(struct cluster * cltr) with (cltr->ready_queue) {
674 /* paranoid */ verify( lanes.count > 0 );
675 unsigned count = __atomic_load_n( &lanes.count, __ATOMIC_RELAXED );
676 unsigned offset = __tls_rand();
677 for(i; count) {
678 unsigned idx = (offset + i) % count;
679 struct thread$ * thrd = try_pop(cltr, idx __STATS(, __tls_stats()->ready.pop.search));
680 if(thrd) {
681 return thrd;
682 }
683 }
684
685 // All lanes where empty return 0p
686 return 0p;
687}
688
689//-----------------------------------------------------------------------
690// Check that all the intrusive queues in the data structure are still consistent
691static void check( __ready_queue_t & q ) with (q) {
692 #if defined(__CFA_WITH_VERIFY__)
693 {
694 for( idx ; lanes.count ) {
695 __intrusive_lane_t & sl = lanes.data[idx];
696 assert(!lanes.data[idx].lock);
697
698 if(is_empty(sl)) {
699 assert( sl.anchor.next == 0p );
700 assert( sl.anchor.ts == -1llu );
701 assert( mock_head(sl) == sl.prev );
702 } else {
703 assert( sl.anchor.next != 0p );
704 assert( sl.anchor.ts != -1llu );
705 assert( mock_head(sl) != sl.prev );
706 }
707 }
708 }
709 #endif
710}
711
712//-----------------------------------------------------------------------
713// Given 2 indexes, pick the list with the oldest push an try to pop from it
714static inline struct thread$ * try_pop(struct cluster * cltr, unsigned i, unsigned j __STATS(, __stats_readyQ_pop_t & stats)) with (cltr->ready_queue) {
715 // Pick the bet list
716 int w = i;
717 if( __builtin_expect(!is_empty(lanes.data[j]), true) ) {
718 w = (ts(lanes.data[i]) < ts(lanes.data[j])) ? i : j;
719 }
720
721 return try_pop(cltr, w __STATS(, stats));
722}
723
724// Call this function of the intrusive list was moved using memcpy
725// fixes the list so that the pointers back to anchors aren't left dangling
726static inline void fix(__intrusive_lane_t & ll) {
727 if(is_empty(ll)) {
728 verify(ll.anchor.next == 0p);
729 ll.prev = mock_head(ll);
730 }
731}
732
733static void assign_list(unsigned & value, dlist(processor) & list, unsigned count) {
734 processor * it = &list`first;
735 for(unsigned i = 0; i < count; i++) {
736 /* paranoid */ verifyf( it, "Unexpected null iterator, at index %u of %u\n", i, count);
737 it->rdq.id = value;
738 it->rdq.target = -1u;
739 value += READYQ_SHARD_FACTOR;
740 it = &(*it)`next;
741 }
742}
743
744static void reassign_cltr_id(struct cluster * cltr) {
745 unsigned preferred = 0;
746 assign_list(preferred, cltr->procs.actives, cltr->procs.total - cltr->procs.idle);
747 assign_list(preferred, cltr->procs.idles , cltr->procs.idle );
748}
749
750static void fix_times( struct cluster * cltr ) with( cltr->ready_queue ) {
751 #if defined(USE_WORK_STEALING)
752 lanes.tscs = alloc(lanes.count, lanes.tscs`realloc);
753 for(i; lanes.count) {
754 unsigned long long tsc1 = ts(lanes.data[i]);
755 unsigned long long tsc2 = rdtscl();
756 lanes.tscs[i].tv = min(tsc1, tsc2);
757 }
758 #endif
759}
760
761#if defined(USE_CPU_WORK_STEALING)
762 // ready_queue size is fixed in this case
763 void ready_queue_grow(struct cluster * cltr) {}
764 void ready_queue_shrink(struct cluster * cltr) {}
765#else
766 // Grow the ready queue
767 void ready_queue_grow(struct cluster * cltr) {
768 size_t ncount;
769 int target = cltr->procs.total;
770
771 /* paranoid */ verify( ready_mutate_islocked() );
772 __cfadbg_print_safe(ready_queue, "Kernel : Growing ready queue\n");
773
774 // Make sure that everything is consistent
775 /* paranoid */ check( cltr->ready_queue );
776
777 // grow the ready queue
778 with( cltr->ready_queue ) {
779 // Find new count
780 // Make sure we always have atleast 1 list
781 if(target >= 2) {
782 ncount = target * READYQ_SHARD_FACTOR;
783 } else {
784 ncount = SEQUENTIAL_SHARD;
785 }
786
787 // Allocate new array (uses realloc and memcpies the data)
788 lanes.data = alloc( ncount, lanes.data`realloc );
789
790 // Fix the moved data
791 for( idx; (size_t)lanes.count ) {
792 fix(lanes.data[idx]);
793 }
794
795 // Construct new data
796 for( idx; (size_t)lanes.count ~ ncount) {
797 (lanes.data[idx]){};
798 }
799
800 // Update original
801 lanes.count = ncount;
802 }
803
804 fix_times(cltr);
805
806 reassign_cltr_id(cltr);
807
808 // Make sure that everything is consistent
809 /* paranoid */ check( cltr->ready_queue );
810
811 __cfadbg_print_safe(ready_queue, "Kernel : Growing ready queue done\n");
812
813 /* paranoid */ verify( ready_mutate_islocked() );
814 }
815
816 // Shrink the ready queue
817 void ready_queue_shrink(struct cluster * cltr) {
818 /* paranoid */ verify( ready_mutate_islocked() );
819 __cfadbg_print_safe(ready_queue, "Kernel : Shrinking ready queue\n");
820
821 // Make sure that everything is consistent
822 /* paranoid */ check( cltr->ready_queue );
823
824 int target = cltr->procs.total;
825
826 with( cltr->ready_queue ) {
827 // Remember old count
828 size_t ocount = lanes.count;
829
830 // Find new count
831 // Make sure we always have atleast 1 list
832 lanes.count = target >= 2 ? target * READYQ_SHARD_FACTOR: SEQUENTIAL_SHARD;
833 /* paranoid */ verify( ocount >= lanes.count );
834 /* paranoid */ verify( lanes.count == target * READYQ_SHARD_FACTOR || target < 2 );
835
836 // for printing count the number of displaced threads
837 #if defined(__CFA_DEBUG_PRINT__) || defined(__CFA_DEBUG_PRINT_READY_QUEUE__)
838 __attribute__((unused)) size_t displaced = 0;
839 #endif
840
841 // redistribute old data
842 for( idx; (size_t)lanes.count ~ ocount) {
843 // Lock is not strictly needed but makes checking invariants much easier
844 __attribute__((unused)) bool locked = __atomic_try_acquire(&lanes.data[idx].lock);
845 verify(locked);
846
847 // As long as we can pop from this lane to push the threads somewhere else in the queue
848 while(!is_empty(lanes.data[idx])) {
849 struct thread$ * thrd;
850 unsigned long long _;
851 [thrd, _] = pop(lanes.data[idx]);
852
853 push(cltr, thrd, true);
854
855 // for printing count the number of displaced threads
856 #if defined(__CFA_DEBUG_PRINT__) || defined(__CFA_DEBUG_PRINT_READY_QUEUE__)
857 displaced++;
858 #endif
859 }
860
861 // Unlock the lane
862 __atomic_unlock(&lanes.data[idx].lock);
863
864 // TODO print the queue statistics here
865
866 ^(lanes.data[idx]){};
867 }
868
869 __cfadbg_print_safe(ready_queue, "Kernel : Shrinking ready queue displaced %zu threads\n", displaced);
870
871 // Allocate new array (uses realloc and memcpies the data)
872 lanes.data = alloc( lanes.count, lanes.data`realloc );
873
874 // Fix the moved data
875 for( idx; (size_t)lanes.count ) {
876 fix(lanes.data[idx]);
877 }
878 }
879
880 fix_times(cltr);
881
882 reassign_cltr_id(cltr);
883
884 // Make sure that everything is consistent
885 /* paranoid */ check( cltr->ready_queue );
886
887 __cfadbg_print_safe(ready_queue, "Kernel : Shrinking ready queue done\n");
888 /* paranoid */ verify( ready_mutate_islocked() );
889 }
890#endif
891
892#if !defined(__CFA_NO_STATISTICS__)
893 unsigned cnt(const __ready_queue_t & this, unsigned idx) {
894 /* paranoid */ verify(this.lanes.count > idx);
895 return this.lanes.data[idx].cnt;
896 }
897#endif
898
899
900#if defined(CFA_HAVE_LINUX_LIBRSEQ)
901 // No definition needed
902#elif defined(CFA_HAVE_LINUX_RSEQ_H)
903
904 #if defined( __x86_64 ) || defined( __i386 )
905 #define RSEQ_SIG 0x53053053
906 #elif defined( __ARM_ARCH )
907 #ifdef __ARMEB__
908 #define RSEQ_SIG 0xf3def5e7 /* udf #24035 ; 0x5de3 (ARMv6+) */
909 #else
910 #define RSEQ_SIG 0xe7f5def3 /* udf #24035 ; 0x5de3 */
911 #endif
912 #endif
913
914 extern void __disable_interrupts_hard();
915 extern void __enable_interrupts_hard();
916
917 void __kernel_raw_rseq_register (void) {
918 /* paranoid */ verify( __cfaabi_rseq.cpu_id == RSEQ_CPU_ID_UNINITIALIZED );
919
920 // int ret = syscall(__NR_rseq, &__cfaabi_rseq, sizeof(struct rseq), 0, (sigset_t *)0p, _NSIG / 8);
921 int ret = syscall(__NR_rseq, &__cfaabi_rseq, sizeof(struct rseq), 0, RSEQ_SIG);
922 if(ret != 0) {
923 int e = errno;
924 switch(e) {
925 case EINVAL: abort("KERNEL ERROR: rseq register invalid argument");
926 case ENOSYS: abort("KERNEL ERROR: rseq register no supported");
927 case EFAULT: abort("KERNEL ERROR: rseq register with invalid argument");
928 case EBUSY : abort("KERNEL ERROR: rseq register already registered");
929 case EPERM : abort("KERNEL ERROR: rseq register sig argument on unregistration does not match the signature received on registration");
930 default: abort("KERNEL ERROR: rseq register unexpected return %d", e);
931 }
932 }
933 }
934
935 void __kernel_raw_rseq_unregister(void) {
936 /* paranoid */ verify( __cfaabi_rseq.cpu_id >= 0 );
937
938 // int ret = syscall(__NR_rseq, &__cfaabi_rseq, sizeof(struct rseq), RSEQ_FLAG_UNREGISTER, (sigset_t *)0p, _NSIG / 8);
939 int ret = syscall(__NR_rseq, &__cfaabi_rseq, sizeof(struct rseq), RSEQ_FLAG_UNREGISTER, RSEQ_SIG);
940 if(ret != 0) {
941 int e = errno;
942 switch(e) {
943 case EINVAL: abort("KERNEL ERROR: rseq unregister invalid argument");
944 case ENOSYS: abort("KERNEL ERROR: rseq unregister no supported");
945 case EFAULT: abort("KERNEL ERROR: rseq unregister with invalid argument");
946 case EBUSY : abort("KERNEL ERROR: rseq unregister already registered");
947 case EPERM : abort("KERNEL ERROR: rseq unregister sig argument on unregistration does not match the signature received on registration");
948 default: abort("KERNEL ERROR: rseq unregisteunexpected return %d", e);
949 }
950 }
951 }
952#else
953 // No definition needed
954#endif
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