summaryrefslogtreecommitdiff
path: root/kernel/rcu/rcuscale.c
blob: 228f143bf935d4028e91af5e67d1dff54ea237c3 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
// SPDX-License-Identifier: GPL-2.0+
/*
 * Read-Copy Update module-based scalability-test facility
 *
 * Copyright (C) IBM Corporation, 2015
 *
 * Authors: Paul E. McKenney <paulmck@linux.ibm.com>
 */

#define pr_fmt(fmt) fmt

#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/kthread.h>
#include <linux/err.h>
#include <linux/spinlock.h>
#include <linux/smp.h>
#include <linux/rcupdate.h>
#include <linux/interrupt.h>
#include <linux/sched.h>
#include <uapi/linux/sched/types.h>
#include <linux/atomic.h>
#include <linux/bitops.h>
#include <linux/completion.h>
#include <linux/moduleparam.h>
#include <linux/percpu.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/freezer.h>
#include <linux/cpu.h>
#include <linux/delay.h>
#include <linux/stat.h>
#include <linux/srcu.h>
#include <linux/slab.h>
#include <asm/byteorder.h>
#include <linux/torture.h>
#include <linux/vmalloc.h>
#include <linux/rcupdate_trace.h>

#include "rcu.h"

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.ibm.com>");

#define SCALE_FLAG "-scale:"
#define SCALEOUT_STRING(s) \
	pr_alert("%s" SCALE_FLAG " %s\n", scale_type, s)
#define VERBOSE_SCALEOUT_STRING(s) \
	do { if (verbose) pr_alert("%s" SCALE_FLAG " %s\n", scale_type, s); } while (0)
#define VERBOSE_SCALEOUT_ERRSTRING(s) \
	do { if (verbose) pr_alert("%s" SCALE_FLAG "!!! %s\n", scale_type, s); } while (0)

/*
 * The intended use cases for the nreaders and nwriters module parameters
 * are as follows:
 *
 * 1.	Specify only the nr_cpus kernel boot parameter.  This will
 *	set both nreaders and nwriters to the value specified by
 *	nr_cpus for a mixed reader/writer test.
 *
 * 2.	Specify the nr_cpus kernel boot parameter, but set
 *	rcuscale.nreaders to zero.  This will set nwriters to the
 *	value specified by nr_cpus for an update-only test.
 *
 * 3.	Specify the nr_cpus kernel boot parameter, but set
 *	rcuscale.nwriters to zero.  This will set nreaders to the
 *	value specified by nr_cpus for a read-only test.
 *
 * Various other use cases may of course be specified.
 *
 * Note that this test's readers are intended only as a test load for
 * the writers.  The reader scalability statistics will be overly
 * pessimistic due to the per-critical-section interrupt disabling,
 * test-end checks, and the pair of calls through pointers.
 */

#ifdef MODULE
# define RCUSCALE_SHUTDOWN 0
#else
# define RCUSCALE_SHUTDOWN 1
#endif

torture_param(bool, gp_async, false, "Use asynchronous GP wait primitives");
torture_param(int, gp_async_max, 1000, "Max # outstanding waits per reader");
torture_param(bool, gp_exp, false, "Use expedited GP wait primitives");
torture_param(int, holdoff, 10, "Holdoff time before test start (s)");
torture_param(int, nreaders, -1, "Number of RCU reader threads");
torture_param(int, nwriters, -1, "Number of RCU updater threads");
torture_param(bool, shutdown, RCUSCALE_SHUTDOWN,
	      "Shutdown at end of scalability tests.");
torture_param(int, verbose, 1, "Enable verbose debugging printk()s");
torture_param(int, writer_holdoff, 0, "Holdoff (us) between GPs, zero to disable");
torture_param(int, kfree_rcu_test, 0, "Do we run a kfree_rcu() scale test?");
torture_param(int, kfree_mult, 1, "Multiple of kfree_obj size to allocate.");

static char *scale_type = "rcu";
module_param(scale_type, charp, 0444);
MODULE_PARM_DESC(scale_type, "Type of RCU to scalability-test (rcu, srcu, ...)");

static int nrealreaders;
static int nrealwriters;
static struct task_struct **writer_tasks;
static struct task_struct **reader_tasks;
static struct task_struct *shutdown_task;

static u64 **writer_durations;
static int *writer_n_durations;
static atomic_t n_rcu_scale_reader_started;
static atomic_t n_rcu_scale_writer_started;
static atomic_t n_rcu_scale_writer_finished;
static wait_queue_head_t shutdown_wq;
static u64 t_rcu_scale_writer_started;
static u64 t_rcu_scale_writer_finished;
static unsigned long b_rcu_gp_test_started;
static unsigned long b_rcu_gp_test_finished;
static DEFINE_PER_CPU(atomic_t, n_async_inflight);

#define MAX_MEAS 10000
#define MIN_MEAS 100

/*
 * Operations vector for selecting different types of tests.
 */

struct rcu_scale_ops {
	int ptype;
	void (*init)(void);
	void (*cleanup)(void);
	int (*readlock)(void);
	void (*readunlock)(int idx);
	unsigned long (*get_gp_seq)(void);
	unsigned long (*gp_diff)(unsigned long new, unsigned long old);
	unsigned long (*exp_completed)(void);
	void (*async)(struct rcu_head *head, rcu_callback_t func);
	void (*gp_barrier)(void);
	void (*sync)(void);
	void (*exp_sync)(void);
	const char *name;
};

static struct rcu_scale_ops *cur_ops;

/*
 * Definitions for rcu scalability testing.
 */

static int rcu_scale_read_lock(void) __acquires(RCU)
{
	rcu_read_lock();
	return 0;
}

static void rcu_scale_read_unlock(int idx) __releases(RCU)
{
	rcu_read_unlock();
}

static unsigned long __maybe_unused rcu_no_completed(void)
{
	return 0;
}

static void rcu_sync_scale_init(void)
{
}

static struct rcu_scale_ops rcu_ops = {
	.ptype		= RCU_FLAVOR,
	.init		= rcu_sync_scale_init,
	.readlock	= rcu_scale_read_lock,
	.readunlock	= rcu_scale_read_unlock,
	.get_gp_seq	= rcu_get_gp_seq,
	.gp_diff	= rcu_seq_diff,
	.exp_completed	= rcu_exp_batches_completed,
	.async		= call_rcu,
	.gp_barrier	= rcu_barrier,
	.sync		= synchronize_rcu,
	.exp_sync	= synchronize_rcu_expedited,
	.name		= "rcu"
};

/*
 * Definitions for srcu scalability testing.
 */

DEFINE_STATIC_SRCU(srcu_ctl_scale);
static struct srcu_struct *srcu_ctlp = &srcu_ctl_scale;

static int srcu_scale_read_lock(void) __acquires(srcu_ctlp)
{
	return srcu_read_lock(srcu_ctlp);
}

static void srcu_scale_read_unlock(int idx) __releases(srcu_ctlp)
{
	srcu_read_unlock(srcu_ctlp, idx);
}

static unsigned long srcu_scale_completed(void)
{
	return srcu_batches_completed(srcu_ctlp);
}

static void srcu_call_rcu(struct rcu_head *head, rcu_callback_t func)
{
	call_srcu(srcu_ctlp, head, func);
}

static void srcu_rcu_barrier(void)
{
	srcu_barrier(srcu_ctlp);
}

static void srcu_scale_synchronize(void)
{
	synchronize_srcu(srcu_ctlp);
}

static void srcu_scale_synchronize_expedited(void)
{
	synchronize_srcu_expedited(srcu_ctlp);
}

static struct rcu_scale_ops srcu_ops = {
	.ptype		= SRCU_FLAVOR,
	.init		= rcu_sync_scale_init,
	.readlock	= srcu_scale_read_lock,
	.readunlock	= srcu_scale_read_unlock,
	.get_gp_seq	= srcu_scale_completed,
	.gp_diff	= rcu_seq_diff,
	.exp_completed	= srcu_scale_completed,
	.async		= srcu_call_rcu,
	.gp_barrier	= srcu_rcu_barrier,
	.sync		= srcu_scale_synchronize,
	.exp_sync	= srcu_scale_synchronize_expedited,
	.name		= "srcu"
};

static struct srcu_struct srcud;

static void srcu_sync_scale_init(void)
{
	srcu_ctlp = &srcud;
	init_srcu_struct(srcu_ctlp);
}

static void srcu_sync_scale_cleanup(void)
{
	cleanup_srcu_struct(srcu_ctlp);
}

static struct rcu_scale_ops srcud_ops = {
	.ptype		= SRCU_FLAVOR,
	.init		= srcu_sync_scale_init,
	.cleanup	= srcu_sync_scale_cleanup,
	.readlock	= srcu_scale_read_lock,
	.readunlock	= srcu_scale_read_unlock,
	.get_gp_seq	= srcu_scale_completed,
	.gp_diff	= rcu_seq_diff,
	.exp_completed	= srcu_scale_completed,
	.async		= srcu_call_rcu,
	.gp_barrier	= srcu_rcu_barrier,
	.sync		= srcu_scale_synchronize,
	.exp_sync	= srcu_scale_synchronize_expedited,
	.name		= "srcud"
};

/*
 * Definitions for RCU-tasks scalability testing.
 */

static int tasks_scale_read_lock(void)
{
	return 0;
}

static void tasks_scale_read_unlock(int idx)
{
}

static struct rcu_scale_ops tasks_ops = {
	.ptype		= RCU_TASKS_FLAVOR,
	.init		= rcu_sync_scale_init,
	.readlock	= tasks_scale_read_lock,
	.readunlock	= tasks_scale_read_unlock,
	.get_gp_seq	= rcu_no_completed,
	.gp_diff	= rcu_seq_diff,
	.async		= call_rcu_tasks,
	.gp_barrier	= rcu_barrier_tasks,
	.sync		= synchronize_rcu_tasks,
	.exp_sync	= synchronize_rcu_tasks,
	.name		= "tasks"
};

/*
 * Definitions for RCU-tasks-trace scalability testing.
 */

static int tasks_trace_scale_read_lock(void)
{
	rcu_read_lock_trace();
	return 0;
}

static void tasks_trace_scale_read_unlock(int idx)
{
	rcu_read_unlock_trace();
}

static struct rcu_scale_ops tasks_tracing_ops = {
	.ptype		= RCU_TASKS_FLAVOR,
	.init		= rcu_sync_scale_init,
	.readlock	= tasks_trace_scale_read_lock,
	.readunlock	= tasks_trace_scale_read_unlock,
	.get_gp_seq	= rcu_no_completed,
	.gp_diff	= rcu_seq_diff,
	.async		= call_rcu_tasks_trace,
	.gp_barrier	= rcu_barrier_tasks_trace,
	.sync		= synchronize_rcu_tasks_trace,
	.exp_sync	= synchronize_rcu_tasks_trace,
	.name		= "tasks-tracing"
};

static unsigned long rcuscale_seq_diff(unsigned long new, unsigned long old)
{
	if (!cur_ops->gp_diff)
		return new - old;
	return cur_ops->gp_diff(new, old);
}

/*
 * If scalability tests complete, wait for shutdown to commence.
 */
static void rcu_scale_wait_shutdown(void)
{
	cond_resched_tasks_rcu_qs();
	if (atomic_read(&n_rcu_scale_writer_finished) < nrealwriters)
		return;
	while (!torture_must_stop())
		schedule_timeout_uninterruptible(1);
}

/*
 * RCU scalability reader kthread.  Repeatedly does empty RCU read-side
 * critical section, minimizing update-side interference.  However, the
 * point of this test is not to evaluate reader scalability, but instead
 * to serve as a test load for update-side scalability testing.
 */
static int
rcu_scale_reader(void *arg)
{
	unsigned long flags;
	int idx;
	long me = (long)arg;

	VERBOSE_SCALEOUT_STRING("rcu_scale_reader task started");
	set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids));
	set_user_nice(current, MAX_NICE);
	atomic_inc(&n_rcu_scale_reader_started);

	do {
		local_irq_save(flags);
		idx = cur_ops->readlock();
		cur_ops->readunlock(idx);
		local_irq_restore(flags);
		rcu_scale_wait_shutdown();
	} while (!torture_must_stop());
	torture_kthread_stopping("rcu_scale_reader");
	return 0;
}

/*
 * Callback function for asynchronous grace periods from rcu_scale_writer().
 */
static void rcu_scale_async_cb(struct rcu_head *rhp)
{
	atomic_dec(this_cpu_ptr(&n_async_inflight));
	kfree(rhp);
}

/*
 * RCU scale writer kthread.  Repeatedly does a grace period.
 */
static int
rcu_scale_writer(void *arg)
{
	int i = 0;
	int i_max;
	long me = (long)arg;
	struct rcu_head *rhp = NULL;
	bool started = false, done = false, alldone = false;
	u64 t;
	u64 *wdp;
	u64 *wdpp = writer_durations[me];

	VERBOSE_SCALEOUT_STRING("rcu_scale_writer task started");
	WARN_ON(!wdpp);
	set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids));
	sched_set_fifo_low(current);

	if (holdoff)
		schedule_timeout_uninterruptible(holdoff * HZ);

	/*
	 * Wait until rcu_end_inkernel_boot() is called for normal GP tests
	 * so that RCU is not always expedited for normal GP tests.
	 * The system_state test is approximate, but works well in practice.
	 */
	while (!gp_exp && system_state != SYSTEM_RUNNING)
		schedule_timeout_uninterruptible(1);

	t = ktime_get_mono_fast_ns();
	if (atomic_inc_return(&n_rcu_scale_writer_started) >= nrealwriters) {
		t_rcu_scale_writer_started = t;
		if (gp_exp) {
			b_rcu_gp_test_started =
				cur_ops->exp_completed() / 2;
		} else {
			b_rcu_gp_test_started = cur_ops->get_gp_seq();
		}
	}

	do {
		if (writer_holdoff)
			udelay(writer_holdoff);
		wdp = &wdpp[i];
		*wdp = ktime_get_mono_fast_ns();
		if (gp_async) {
retry:
			if (!rhp)
				rhp = kmalloc(sizeof(*rhp), GFP_KERNEL);
			if (rhp && atomic_read(this_cpu_ptr(&n_async_inflight)) < gp_async_max) {
				atomic_inc(this_cpu_ptr(&n_async_inflight));
				cur_ops->async(rhp, rcu_scale_async_cb);
				rhp = NULL;
			} else if (!kthread_should_stop()) {
				cur_ops->gp_barrier();
				goto retry;
			} else {
				kfree(rhp); /* Because we are stopping. */
			}
		} else if (gp_exp) {
			cur_ops->exp_sync();
		} else {
			cur_ops->sync();
		}
		t = ktime_get_mono_fast_ns();
		*wdp = t - *wdp;
		i_max = i;
		if (!started &&
		    atomic_read(&n_rcu_scale_writer_started) >= nrealwriters)
			started = true;
		if (!done && i >= MIN_MEAS) {
			done = true;
			sched_set_normal(current, 0);
			pr_alert("%s%s rcu_scale_writer %ld has %d measurements\n",
				 scale_type, SCALE_FLAG, me, MIN_MEAS);
			if (atomic_inc_return(&n_rcu_scale_writer_finished) >=
			    nrealwriters) {
				schedule_timeout_interruptible(10);
				rcu_ftrace_dump(DUMP_ALL);
				SCALEOUT_STRING("Test complete");
				t_rcu_scale_writer_finished = t;
				if (gp_exp) {
					b_rcu_gp_test_finished =
						cur_ops->exp_completed() / 2;
				} else {
					b_rcu_gp_test_finished =
						cur_ops->get_gp_seq();
				}
				if (shutdown) {
					smp_mb(); /* Assign before wake. */
					wake_up(&shutdown_wq);
				}
			}
		}
		if (done && !alldone &&
		    atomic_read(&n_rcu_scale_writer_finished) >= nrealwriters)
			alldone = true;
		if (started && !alldone && i < MAX_MEAS - 1)
			i++;
		rcu_scale_wait_shutdown();
	} while (!torture_must_stop());
	if (gp_async) {
		cur_ops->gp_barrier();
	}
	writer_n_durations[me] = i_max + 1;
	torture_kthread_stopping("rcu_scale_writer");
	return 0;
}

static void
rcu_scale_print_module_parms(struct rcu_scale_ops *cur_ops, const char *tag)
{
	pr_alert("%s" SCALE_FLAG
		 "--- %s: nreaders=%d nwriters=%d verbose=%d shutdown=%d\n",
		 scale_type, tag, nrealreaders, nrealwriters, verbose, shutdown);
}

static void
rcu_scale_cleanup(void)
{
	int i;
	int j;
	int ngps = 0;
	u64 *wdp;
	u64 *wdpp;

	/*
	 * Would like warning at start, but everything is expedited
	 * during the mid-boot phase, so have to wait till the end.
	 */
	if (rcu_gp_is_expedited() && !rcu_gp_is_normal() && !gp_exp)
		VERBOSE_SCALEOUT_ERRSTRING("All grace periods expedited, no normal ones to measure!");
	if (rcu_gp_is_normal() && gp_exp)
		VERBOSE_SCALEOUT_ERRSTRING("All grace periods normal, no expedited ones to measure!");
	if (gp_exp && gp_async)
		VERBOSE_SCALEOUT_ERRSTRING("No expedited async GPs, so went with async!");

	if (torture_cleanup_begin())
		return;
	if (!cur_ops) {
		torture_cleanup_end();
		return;
	}

	if (reader_tasks) {
		for (i = 0; i < nrealreaders; i++)
			torture_stop_kthread(rcu_scale_reader,
					     reader_tasks[i]);
		kfree(reader_tasks);
	}

	if (writer_tasks) {
		for (i = 0; i < nrealwriters; i++) {
			torture_stop_kthread(rcu_scale_writer,
					     writer_tasks[i]);
			if (!writer_n_durations)
				continue;
			j = writer_n_durations[i];
			pr_alert("%s%s writer %d gps: %d\n",
				 scale_type, SCALE_FLAG, i, j);
			ngps += j;
		}
		pr_alert("%s%s start: %llu end: %llu duration: %llu gps: %d batches: %ld\n",
			 scale_type, SCALE_FLAG,
			 t_rcu_scale_writer_started, t_rcu_scale_writer_finished,
			 t_rcu_scale_writer_finished -
			 t_rcu_scale_writer_started,
			 ngps,
			 rcuscale_seq_diff(b_rcu_gp_test_finished,
					   b_rcu_gp_test_started));
		for (i = 0; i < nrealwriters; i++) {
			if (!writer_durations)
				break;
			if (!writer_n_durations)
				continue;
			wdpp = writer_durations[i];
			if (!wdpp)
				continue;
			for (j = 0; j < writer_n_durations[i]; j++) {
				wdp = &wdpp[j];
				pr_alert("%s%s %4d writer-duration: %5d %llu\n",
					scale_type, SCALE_FLAG,
					i, j, *wdp);
				if (j % 100 == 0)
					schedule_timeout_uninterruptible(1);
			}
			kfree(writer_durations[i]);
		}
		kfree(writer_tasks);
		kfree(writer_durations);
		kfree(writer_n_durations);
	}

	/* Do torture-type-specific cleanup operations.  */
	if (cur_ops->cleanup != NULL)
		cur_ops->cleanup();

	torture_cleanup_end();
}

/*
 * Return the number if non-negative.  If -1, the number of CPUs.
 * If less than -1, that much less than the number of CPUs, but
 * at least one.
 */
static int compute_real(int n)
{
	int nr;

	if (n >= 0) {
		nr = n;
	} else {
		nr = num_online_cpus() + 1 + n;
		if (nr <= 0)
			nr = 1;
	}
	return nr;
}

/*
 * RCU scalability shutdown kthread.  Just waits to be awakened, then shuts
 * down system.
 */
static int
rcu_scale_shutdown(void *arg)
{
	wait_event(shutdown_wq,
		   atomic_read(&n_rcu_scale_writer_finished) >= nrealwriters);
	smp_mb(); /* Wake before output. */
	rcu_scale_cleanup();
	kernel_power_off();
	return -EINVAL;
}

/*
 * kfree_rcu() scalability tests: Start a kfree_rcu() loop on all CPUs for number
 * of iterations and measure total time and number of GP for all iterations to complete.
 */

torture_param(int, kfree_nthreads, -1, "Number of threads running loops of kfree_rcu().");
torture_param(int, kfree_alloc_num, 8000, "Number of allocations and frees done in an iteration.");
torture_param(int, kfree_loops, 10, "Number of loops doing kfree_alloc_num allocations and frees.");
torture_param(bool, kfree_rcu_test_double, false, "Do we run a kfree_rcu() double-argument scale test?");
torture_param(bool, kfree_rcu_test_single, false, "Do we run a kfree_rcu() single-argument scale test?");

static struct task_struct **kfree_reader_tasks;
static int kfree_nrealthreads;
static atomic_t n_kfree_scale_thread_started;
static atomic_t n_kfree_scale_thread_ended;

struct kfree_obj {
	char kfree_obj[8];
	struct rcu_head rh;
};

static int
kfree_scale_thread(void *arg)
{
	int i, loop = 0;
	long me = (long)arg;
	struct kfree_obj *alloc_ptr;
	u64 start_time, end_time;
	long long mem_begin, mem_during = 0;
	bool kfree_rcu_test_both;
	DEFINE_TORTURE_RANDOM(tr);

	VERBOSE_SCALEOUT_STRING("kfree_scale_thread task started");
	set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids));
	set_user_nice(current, MAX_NICE);
	kfree_rcu_test_both = (kfree_rcu_test_single == kfree_rcu_test_double);

	start_time = ktime_get_mono_fast_ns();

	if (atomic_inc_return(&n_kfree_scale_thread_started) >= kfree_nrealthreads) {
		if (gp_exp)
			b_rcu_gp_test_started = cur_ops->exp_completed() / 2;
		else
			b_rcu_gp_test_started = cur_ops->get_gp_seq();
	}

	do {
		if (!mem_during) {
			mem_during = mem_begin = si_mem_available();
		} else if (loop % (kfree_loops / 4) == 0) {
			mem_during = (mem_during + si_mem_available()) / 2;
		}

		for (i = 0; i < kfree_alloc_num; i++) {
			alloc_ptr = kmalloc(kfree_mult * sizeof(struct kfree_obj), GFP_KERNEL);
			if (!alloc_ptr)
				return -ENOMEM;

			// By default kfree_rcu_test_single and kfree_rcu_test_double are
			// initialized to false. If both have the same value (false or true)
			// both are randomly tested, otherwise only the one with value true
			// is tested.
			if ((kfree_rcu_test_single && !kfree_rcu_test_double) ||
					(kfree_rcu_test_both && torture_random(&tr) & 0x800))
				kfree_rcu(alloc_ptr);
			else
				kfree_rcu(alloc_ptr, rh);
		}

		cond_resched();
	} while (!torture_must_stop() && ++loop < kfree_loops);

	if (atomic_inc_return(&n_kfree_scale_thread_ended) >= kfree_nrealthreads) {
		end_time = ktime_get_mono_fast_ns();

		if (gp_exp)
			b_rcu_gp_test_finished = cur_ops->exp_completed() / 2;
		else
			b_rcu_gp_test_finished = cur_ops->get_gp_seq();

		pr_alert("Total time taken by all kfree'ers: %llu ns, loops: %d, batches: %ld, memory footprint: %lldMB\n",
		       (unsigned long long)(end_time - start_time), kfree_loops,
		       rcuscale_seq_diff(b_rcu_gp_test_finished, b_rcu_gp_test_started),
		       (mem_begin - mem_during) >> (20 - PAGE_SHIFT));

		if (shutdown) {
			smp_mb(); /* Assign before wake. */
			wake_up(&shutdown_wq);
		}
	}

	torture_kthread_stopping("kfree_scale_thread");
	return 0;
}

static void
kfree_scale_cleanup(void)
{
	int i;

	if (torture_cleanup_begin())
		return;

	if (kfree_reader_tasks) {
		for (i = 0; i < kfree_nrealthreads; i++)
			torture_stop_kthread(kfree_scale_thread,
					     kfree_reader_tasks[i]);
		kfree(kfree_reader_tasks);
	}

	torture_cleanup_end();
}

/*
 * shutdown kthread.  Just waits to be awakened, then shuts down system.
 */
static int
kfree_scale_shutdown(void *arg)
{
	wait_event(shutdown_wq,
		   atomic_read(&n_kfree_scale_thread_ended) >= kfree_nrealthreads);

	smp_mb(); /* Wake before output. */

	kfree_scale_cleanup();
	kernel_power_off();
	return -EINVAL;
}

static int __init
kfree_scale_init(void)
{
	long i;
	int firsterr = 0;

	kfree_nrealthreads = compute_real(kfree_nthreads);
	/* Start up the kthreads. */
	if (shutdown) {
		init_waitqueue_head(&shutdown_wq);
		firsterr = torture_create_kthread(kfree_scale_shutdown, NULL,
						  shutdown_task);
		if (torture_init_error(firsterr))
			goto unwind;
		schedule_timeout_uninterruptible(1);
	}

	pr_alert("kfree object size=%zu\n", kfree_mult * sizeof(struct kfree_obj));

	kfree_reader_tasks = kcalloc(kfree_nrealthreads, sizeof(kfree_reader_tasks[0]),
			       GFP_KERNEL);
	if (kfree_reader_tasks == NULL) {
		firsterr = -ENOMEM;
		goto unwind;
	}

	for (i = 0; i < kfree_nrealthreads; i++) {
		firsterr = torture_create_kthread(kfree_scale_thread, (void *)i,
						  kfree_reader_tasks[i]);
		if (torture_init_error(firsterr))
			goto unwind;
	}

	while (atomic_read(&n_kfree_scale_thread_started) < kfree_nrealthreads)
		schedule_timeout_uninterruptible(1);

	torture_init_end();
	return 0;

unwind:
	torture_init_end();
	kfree_scale_cleanup();
	return firsterr;
}

static int __init
rcu_scale_init(void)
{
	long i;
	int firsterr = 0;
	static struct rcu_scale_ops *scale_ops[] = {
		&rcu_ops, &srcu_ops, &srcud_ops, &tasks_ops, &tasks_tracing_ops
	};

	if (!torture_init_begin(scale_type, verbose))
		return -EBUSY;

	/* Process args and announce that the scalability'er is on the job. */
	for (i = 0; i < ARRAY_SIZE(scale_ops); i++) {
		cur_ops = scale_ops[i];
		if (strcmp(scale_type, cur_ops->name) == 0)
			break;
	}
	if (i == ARRAY_SIZE(scale_ops)) {
		pr_alert("rcu-scale: invalid scale type: \"%s\"\n", scale_type);
		pr_alert("rcu-scale types:");
		for (i = 0; i < ARRAY_SIZE(scale_ops); i++)
			pr_cont(" %s", scale_ops[i]->name);
		pr_cont("\n");
		firsterr = -EINVAL;
		cur_ops = NULL;
		goto unwind;
	}
	if (cur_ops->init)
		cur_ops->init();

	if (kfree_rcu_test)
		return kfree_scale_init();

	nrealwriters = compute_real(nwriters);
	nrealreaders = compute_real(nreaders);
	atomic_set(&n_rcu_scale_reader_started, 0);
	atomic_set(&n_rcu_scale_writer_started, 0);
	atomic_set(&n_rcu_scale_writer_finished, 0);
	rcu_scale_print_module_parms(cur_ops, "Start of test");

	/* Start up the kthreads. */

	if (shutdown) {
		init_waitqueue_head(&shutdown_wq);
		firsterr = torture_create_kthread(rcu_scale_shutdown, NULL,
						  shutdown_task);
		if (torture_init_error(firsterr))
			goto unwind;
		schedule_timeout_uninterruptible(1);
	}
	reader_tasks = kcalloc(nrealreaders, sizeof(reader_tasks[0]),
			       GFP_KERNEL);
	if (reader_tasks == NULL) {
		VERBOSE_SCALEOUT_ERRSTRING("out of memory");
		firsterr = -ENOMEM;
		goto unwind;
	}
	for (i = 0; i < nrealreaders; i++) {
		firsterr = torture_create_kthread(rcu_scale_reader, (void *)i,
						  reader_tasks[i]);
		if (torture_init_error(firsterr))
			goto unwind;
	}
	while (atomic_read(&n_rcu_scale_reader_started) < nrealreaders)
		schedule_timeout_uninterruptible(1);
	writer_tasks = kcalloc(nrealwriters, sizeof(reader_tasks[0]),
			       GFP_KERNEL);
	writer_durations = kcalloc(nrealwriters, sizeof(*writer_durations),
				   GFP_KERNEL);
	writer_n_durations =
		kcalloc(nrealwriters, sizeof(*writer_n_durations),
			GFP_KERNEL);
	if (!writer_tasks || !writer_durations || !writer_n_durations) {
		VERBOSE_SCALEOUT_ERRSTRING("out of memory");
		firsterr = -ENOMEM;
		goto unwind;
	}
	for (i = 0; i < nrealwriters; i++) {
		writer_durations[i] =
			kcalloc(MAX_MEAS, sizeof(*writer_durations[i]),
				GFP_KERNEL);
		if (!writer_durations[i]) {
			firsterr = -ENOMEM;
			goto unwind;
		}
		firsterr = torture_create_kthread(rcu_scale_writer, (void *)i,
						  writer_tasks[i]);
		if (torture_init_error(firsterr))
			goto unwind;
	}
	torture_init_end();
	return 0;

unwind:
	torture_init_end();
	rcu_scale_cleanup();
	if (shutdown) {
		WARN_ON(!IS_MODULE(CONFIG_RCU_SCALE_TEST));
		kernel_power_off();
	}
	return firsterr;
}

module_init(rcu_scale_init);
module_exit(rcu_scale_cleanup);