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2023-12-08 01573e231f18eb2d99162747186f59511f56b64d 
 kernel/kernel/locking/qspinlock_stat.h
....@@ -1,255 +1,105 @@
1
+/* SPDX-License-Identifier: GPL-2.0-or-later */
12 /*
2
- * This program is free software; you can redistribute it and/or modify
3
- * it under the terms of the GNU General Public License as published by
4
- * the Free Software Foundation; either version 2 of the License, or
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- * (at your option) any later version.
63  *
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- * This program is distributed in the hope that it will be useful,
8
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
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- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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- * GNU General Public License for more details.
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- *
12
- * Authors: Waiman Long <waiman.long@hpe.com>
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+ * Authors: Waiman Long <longman@redhat.com>
135  */
146 
15
-/*
16
- * When queued spinlock statistical counters are enabled, the following
17
- * debugfs files will be created for reporting the counter values:
18
- *
19
- * <debugfs>/qlockstat/
20
- *   pv_hash_hops	- average # of hops per hashing operation
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- *   pv_kick_unlock	- # of vCPU kicks issued at unlock time
22
- *   pv_kick_wake	- # of vCPU kicks used for computing pv_latency_wake
23
- *   pv_latency_kick	- average latency (ns) of vCPU kick operation
24
- *   pv_latency_wake	- average latency (ns) from vCPU kick to wakeup
25
- *   pv_lock_stealing	- # of lock stealing operations
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- *   pv_spurious_wakeup	- # of spurious wakeups in non-head vCPUs
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- *   pv_wait_again	- # of wait's after a queue head vCPU kick
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- *   pv_wait_early	- # of early vCPU wait's
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- *   pv_wait_head	- # of vCPU wait's at the queue head
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- *   pv_wait_node	- # of vCPU wait's at a non-head queue node
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- *   lock_pending	- # of locking operations via pending code
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- *   lock_slowpath	- # of locking operations via MCS lock queue
33
- *
34
- * Writing to the "reset_counters" file will reset all the above counter
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- * values.
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- *
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- * These statistical counters are implemented as per-cpu variables which are
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- * summed and computed whenever the corresponding debugfs files are read. This
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- * minimizes added overhead making the counters usable even in a production
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- * environment.
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- *
42
- * There may be slight difference between pv_kick_wake and pv_kick_unlock.
43
- */
44
-enum qlock_stats {
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-	qstat_pv_hash_hops,
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-	qstat_pv_kick_unlock,
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-	qstat_pv_kick_wake,
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-	qstat_pv_latency_kick,
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-	qstat_pv_latency_wake,
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-	qstat_pv_lock_stealing,
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-	qstat_pv_spurious_wakeup,
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-	qstat_pv_wait_again,
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-	qstat_pv_wait_early,
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-	qstat_pv_wait_head,
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-	qstat_pv_wait_node,
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-	qstat_lock_pending,
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-	qstat_lock_slowpath,
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-	qstat_num,	/* Total number of statistical counters */
59
-	qstat_reset_cnts = qstat_num,
60
-};
7
+#include "lock_events.h"
618 
62
-#ifdef CONFIG_QUEUED_LOCK_STAT
9
+#ifdef CONFIG_LOCK_EVENT_COUNTS
10
+#ifdef CONFIG_PARAVIRT_SPINLOCKS
6311 /*
64
- * Collect pvqspinlock statistics
12
+ * Collect pvqspinlock locking event counts
6513  */
66
-#include <linux/debugfs.h>
6714 #include <linux/sched.h>
6815 #include <linux/sched/clock.h>
6916 #include <linux/fs.h>
7017 
71
-static const char * const qstat_names[qstat_num + 1] = {
72
-	[qstat_pv_hash_hops]	   = "pv_hash_hops",
73
-	[qstat_pv_kick_unlock]     = "pv_kick_unlock",
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-	[qstat_pv_kick_wake]       = "pv_kick_wake",
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-	[qstat_pv_spurious_wakeup] = "pv_spurious_wakeup",
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-	[qstat_pv_latency_kick]	   = "pv_latency_kick",
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-	[qstat_pv_latency_wake]    = "pv_latency_wake",
78
-	[qstat_pv_lock_stealing]   = "pv_lock_stealing",
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-	[qstat_pv_wait_again]      = "pv_wait_again",
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-	[qstat_pv_wait_early]      = "pv_wait_early",
81
-	[qstat_pv_wait_head]       = "pv_wait_head",
82
-	[qstat_pv_wait_node]       = "pv_wait_node",
83
-	[qstat_lock_pending]       = "lock_pending",
84
-	[qstat_lock_slowpath]      = "lock_slowpath",
85
-	[qstat_reset_cnts]         = "reset_counters",
86
-};
18
+#define EVENT_COUNT(ev)	lockevents[LOCKEVENT_ ## ev]
8719 
8820 /*
89
- * Per-cpu counters
21
+ * PV specific per-cpu counter
9022  */
91
-static DEFINE_PER_CPU(unsigned long, qstats[qstat_num]);
9223 static DEFINE_PER_CPU(u64, pv_kick_time);
9324 
9425 /*
95
- * Function to read and return the qlock statistical counter values
26
+ * Function to read and return the PV qspinlock counts.
9627  *
9728  * The following counters are handled specially:
98
- * 1. qstat_pv_latency_kick
29
+ * 1. pv_latency_kick
9930  *    Average kick latency (ns) = pv_latency_kick/pv_kick_unlock
100
- * 2. qstat_pv_latency_wake
31
+ * 2. pv_latency_wake
10132  *    Average wake latency (ns) = pv_latency_wake/pv_kick_wake
102
- * 3. qstat_pv_hash_hops
33
+ * 3. pv_hash_hops
10334  *    Average hops/hash = pv_hash_hops/pv_kick_unlock
10435  */
105
-static ssize_t qstat_read(struct file *file, char __user *user_buf,
106
-			  size_t count, loff_t *ppos)
36
+ssize_t lockevent_read(struct file *file, char __user *user_buf,
37
+		       size_t count, loff_t *ppos)
10738 {
10839 	char buf[64];
109
-	int cpu, counter, len;
110
-	u64 stat = 0, kicks = 0;
40
+	int cpu, id, len;
41
+	u64 sum = 0, kicks = 0;
11142 
11243 	/*
11344 	 * Get the counter ID stored in file->f_inode->i_private
11445 	 */
115
-	counter = (long)file_inode(file)->i_private;
46
+	id = (long)file_inode(file)->i_private;
11647 
117
-	if (counter >= qstat_num)
48
+	if (id >= lockevent_num)
11849 		return -EBADF;
11950 
12051 	for_each_possible_cpu(cpu) {
121
-		stat += per_cpu(qstats[counter], cpu);
52
+		sum += per_cpu(lockevents[id], cpu);
12253 		/*
123
-		 * Need to sum additional counter for some of them
54
+		 * Need to sum additional counters for some of them
12455 		 */
125
-		switch (counter) {
56
+		switch (id) {
12657 
127
-		case qstat_pv_latency_kick:
128
-		case qstat_pv_hash_hops:
129
-			kicks += per_cpu(qstats[qstat_pv_kick_unlock], cpu);
58
+		case LOCKEVENT_pv_latency_kick:
59
+		case LOCKEVENT_pv_hash_hops:
60
+			kicks += per_cpu(EVENT_COUNT(pv_kick_unlock), cpu);
13061 			break;
13162 
132
-		case qstat_pv_latency_wake:
133
-			kicks += per_cpu(qstats[qstat_pv_kick_wake], cpu);
63
+		case LOCKEVENT_pv_latency_wake:
64
+			kicks += per_cpu(EVENT_COUNT(pv_kick_wake), cpu);
13465 			break;
13566 		}
13667 	}
13768 
138
-	if (counter == qstat_pv_hash_hops) {
69
+	if (id == LOCKEVENT_pv_hash_hops) {
13970 		u64 frac = 0;
14071 
14172 		if (kicks) {
142
-			frac = 100ULL * do_div(stat, kicks);
73
+			frac = 100ULL * do_div(sum, kicks);
14374 			frac = DIV_ROUND_CLOSEST_ULL(frac, kicks);
14475 		}
14576 
14677 		/*
14778 		 * Return a X.XX decimal number
14879 		 */
149
-		len = snprintf(buf, sizeof(buf) - 1, "%llu.%02llu\n", stat, frac);
80
+		len = snprintf(buf, sizeof(buf) - 1, "%llu.%02llu\n",
81
+			       sum, frac);
15082 	} else {
15183 		/*
15284 		 * Round to the nearest ns
15385 		 */
154
-		if ((counter == qstat_pv_latency_kick) ||
155
-		    (counter == qstat_pv_latency_wake)) {
86
+		if ((id == LOCKEVENT_pv_latency_kick) ||
87
+		    (id == LOCKEVENT_pv_latency_wake)) {
15688 			if (kicks)
157
-				stat = DIV_ROUND_CLOSEST_ULL(stat, kicks);
89
+				sum = DIV_ROUND_CLOSEST_ULL(sum, kicks);
15890 		}
159
-		len = snprintf(buf, sizeof(buf) - 1, "%llu\n", stat);
91
+		len = snprintf(buf, sizeof(buf) - 1, "%llu\n", sum);
16092 	}
16193 
16294 	return simple_read_from_buffer(user_buf, count, ppos, buf, len);
16395 }
16496 
16597 /*
166
- * Function to handle write request
167
- *
168
- * When counter = reset_cnts, reset all the counter values.
169
- * Since the counter updates aren't atomic, the resetting is done twice
170
- * to make sure that the counters are very likely to be all cleared.
171
- */
172
-static ssize_t qstat_write(struct file *file, const char __user *user_buf,
173
-			   size_t count, loff_t *ppos)
174
-{
175
-	int cpu;
176
-
177
-	/*
178
-	 * Get the counter ID stored in file->f_inode->i_private
179
-	 */
180
-	if ((long)file_inode(file)->i_private != qstat_reset_cnts)
181
-		return count;
182
-
183
-	for_each_possible_cpu(cpu) {
184
-		int i;
185
-		unsigned long *ptr = per_cpu_ptr(qstats, cpu);
186
-
187
-		for (i = 0 ; i < qstat_num; i++)
188
-			WRITE_ONCE(ptr[i], 0);
189
-	}
190
-	return count;
191
-}
192
-
193
-/*
194
- * Debugfs data structures
195
- */
196
-static const struct file_operations fops_qstat = {
197
-	.read = qstat_read,
198
-	.write = qstat_write,
199
-	.llseek = default_llseek,
200
-};
201
-
202
-/*
203
- * Initialize debugfs for the qspinlock statistical counters
204
- */
205
-static int __init init_qspinlock_stat(void)
206
-{
207
-	struct dentry *d_qstat = debugfs_create_dir("qlockstat", NULL);
208
-	int i;
209
-
210
-	if (!d_qstat)
211
-		goto out;
212
-
213
-	/*
214
-	 * Create the debugfs files
215
-	 *
216
-	 * As reading from and writing to the stat files can be slow, only
217
-	 * root is allowed to do the read/write to limit impact to system
218
-	 * performance.
219
-	 */
220
-	for (i = 0; i < qstat_num; i++)
221
-		if (!debugfs_create_file(qstat_names[i], 0400, d_qstat,
222
-					 (void *)(long)i, &fops_qstat))
223
-			goto fail_undo;
224
-
225
-	if (!debugfs_create_file(qstat_names[qstat_reset_cnts], 0200, d_qstat,
226
-				 (void *)(long)qstat_reset_cnts, &fops_qstat))
227
-		goto fail_undo;
228
-
229
-	return 0;
230
-fail_undo:
231
-	debugfs_remove_recursive(d_qstat);
232
-out:
233
-	pr_warn("Could not create 'qlockstat' debugfs entries\n");
234
-	return -ENOMEM;
235
-}
236
-fs_initcall(init_qspinlock_stat);
237
-
238
-/*
239
- * Increment the PV qspinlock statistical counters
240
- */
241
-static inline void qstat_inc(enum qlock_stats stat, bool cond)
242
-{
243
-	if (cond)
244
-		this_cpu_inc(qstats[stat]);
245
-}
246
-
247
-/*
24898  * PV hash hop count
24999  */
250
-static inline void qstat_hop(int hopcnt)
100
+static inline void lockevent_pv_hop(int hopcnt)
251101 {
252
-	this_cpu_add(qstats[qstat_pv_hash_hops], hopcnt);
102
+	this_cpu_add(EVENT_COUNT(pv_hash_hops), hopcnt);
253103 }
254104 
255105 /*
....@@ -261,7 +111,7 @@
261111 
262112 	per_cpu(pv_kick_time, cpu) = start;
263113 	pv_kick(cpu);
264
-	this_cpu_add(qstats[qstat_pv_latency_kick], sched_clock() - start);
114
+	this_cpu_add(EVENT_COUNT(pv_latency_kick), sched_clock() - start);
265115 }
266116 
267117 /*
....@@ -274,18 +124,19 @@
274124 	*pkick_time = 0;
275125 	pv_wait(ptr, val);
276126 	if (*pkick_time) {
277
-		this_cpu_add(qstats[qstat_pv_latency_wake],
127
+		this_cpu_add(EVENT_COUNT(pv_latency_wake),
278128 			     sched_clock() - *pkick_time);
279
-		qstat_inc(qstat_pv_kick_wake, true);
129
+		lockevent_inc(pv_kick_wake);
280130 	}
281131 }
282132 
283133 #define pv_kick(c)	__pv_kick(c)
284134 #define pv_wait(p, v)	__pv_wait(p, v)
285135 
286
-#else /* CONFIG_QUEUED_LOCK_STAT */
136
+#endif /* CONFIG_PARAVIRT_SPINLOCKS */
287137 
288
-static inline void qstat_inc(enum qlock_stats stat, bool cond)	{ }
289
-static inline void qstat_hop(int hopcnt)			{ }
138
+#else /* CONFIG_LOCK_EVENT_COUNTS */
290139 
291
-#endif /* CONFIG_QUEUED_LOCK_STAT */
140
+static inline void lockevent_pv_hop(int hopcnt)	{ }
141
+
142
+#endif /* CONFIG_LOCK_EVENT_COUNTS */