1 /*
2 * Copyright (c) 2018 Google, Inc.
3 *
4 * SPDX-License-Identifier: GPL-2.0-or-later
5 *
6 * Task starts out as a CPU hog and then becomes small.
7 * Task placement and downmigration latency are verified.
8 */
9
10 #define _GNU_SOURCE
11 #include <errno.h>
12 #include <pthread.h>
13 #include <sched.h>
14 #include <time.h>
15
16 #include "tst_test.h"
17 #include "tst_safe_file_ops.h"
18 #include "tst_safe_pthread.h"
19
20 #include "trace_parse.h"
21 #include "util.h"
22
23 #define TRACE_EVENTS "sched_switch"
24
25 static int task_tid;
26
27 #define MAX_DOWNMIGRATE_LATENCY_US 100000
28 #define MAX_INCORRECT_CLUSTER_PCT 10
29 #define BURN_SEC 3
task_fn(void * arg LTP_ATTRIBUTE_UNUSED)30 static void *task_fn(void *arg LTP_ATTRIBUTE_UNUSED)
31 {
32 task_tid = gettid();
33
34 printf("Big task executing for %ds...\n", BURN_SEC);
35 burn(BURN_SEC * USEC_PER_SEC, 0);
36
37 printf("Changing to small task...\n");
38 SAFE_FILE_PRINTF(TRACING_DIR "trace_marker", "SMALL TASK");
39 burn(BURN_SEC * USEC_PER_SEC, 1);
40
41 return NULL;
42 }
43
parse_results(void)44 static int parse_results(void)
45 {
46 int i, pct, rv = 0;
47 unsigned long long exec_start_us = 0;
48 unsigned long long too_big_cpu_us = 0;
49 unsigned long long too_small_cpu_us = 0;
50 unsigned long long big_task_us = 0;
51 unsigned long long small_task_us = 0;
52 unsigned long long smalltask_ts_usec = 0;
53 unsigned long long downmigrate_ts_usec = 0;
54 unsigned long long downmigrate_latency_usec = 0;
55 cpu_set_t cpuset;
56
57 if (find_cpus_with_capacity(0, &cpuset)) {
58 printf("Failed to find the CPUs in the little cluster.\n");
59 return -1;
60 }
61
62 for (i = 0; i < num_trace_records; i++) {
63 unsigned long long segment_us;
64 struct trace_sched_switch *t = trace[i].event_data;
65
66 if (trace[i].event_type == TRACE_RECORD_TRACING_MARK_WRITE &&
67 !strcmp(trace[i].event_data, "SMALL TASK")) {
68 smalltask_ts_usec = TS_TO_USEC(trace[i].ts);
69 continue;
70 }
71
72 if (trace[i].event_type != TRACE_RECORD_SCHED_SWITCH)
73 continue;
74
75 if (t->next_pid == task_tid) {
76 /* Start of task execution segment. */
77 if (exec_start_us) {
78 printf("Trace parse fail: double exec start\n");
79 return -1;
80 }
81 exec_start_us = TS_TO_USEC(trace[i].ts);
82 if (smalltask_ts_usec && !downmigrate_ts_usec &&
83 CPU_ISSET(trace[i].cpu, &cpuset))
84 downmigrate_ts_usec = exec_start_us;
85 continue;
86 }
87 if (t->prev_pid != task_tid)
88 continue;
89 /* End of task execution segment. */
90 segment_us = TS_TO_USEC(trace[i].ts);
91 segment_us -= exec_start_us;
92 exec_start_us = 0;
93 if (CPU_ISSET(trace[i].cpu, &cpuset)) {
94 /* Task is running on little CPUs. */
95 if (!smalltask_ts_usec)
96 too_small_cpu_us += segment_us;
97 } else {
98 /* Task is running on big CPUs. */
99 if (smalltask_ts_usec) {
100 /*
101 * Downmigration is accounted separately, so
102 * only record mis-scheduled time here if it
103 * happened after downmigration.
104 */
105 if (downmigrate_ts_usec)
106 too_big_cpu_us += segment_us;
107 }
108 }
109 if (smalltask_ts_usec)
110 small_task_us += segment_us;
111 else
112 big_task_us += segment_us;
113 }
114
115 pct = (too_small_cpu_us * 100) / big_task_us;
116 rv |= (pct > MAX_INCORRECT_CLUSTER_PCT);
117 printf("Time incorrectly scheduled on small when task was big: "
118 "%lld usec (%d%% of big task CPU time)\n", too_small_cpu_us,
119 pct);
120 pct = (too_big_cpu_us * 100) / small_task_us;
121 rv |= (pct > MAX_INCORRECT_CLUSTER_PCT);
122 printf("Time incorrectly scheduled on big when task was small, after "
123 "downmigration: %lld usec (%d%% of small task CPU time)\n",
124 too_big_cpu_us, pct);
125
126 if (downmigrate_ts_usec) {
127 downmigrate_latency_usec = downmigrate_ts_usec -
128 smalltask_ts_usec;
129 printf("Downmigration latency: %lld usec\n",
130 downmigrate_latency_usec);
131 } else {
132 printf("Task never downmigrated!\n");
133 downmigrate_latency_usec = UINT_MAX;
134 }
135
136 return (rv || downmigrate_latency_usec > MAX_DOWNMIGRATE_LATENCY_US);
137 }
138
run(void)139 static void run(void)
140 {
141 pthread_t task_thread;
142
143 tst_res(TINFO, "Maximum incorrect cluster time percentage: %d%%",
144 MAX_INCORRECT_CLUSTER_PCT);
145 tst_res(TINFO, "Maximum downmigration latency: %d usec",
146 MAX_DOWNMIGRATE_LATENCY_US);
147
148 /* configure and enable tracing */
149 SAFE_FILE_PRINTF(TRACING_DIR "tracing_on", "0");
150 SAFE_FILE_PRINTF(TRACING_DIR "buffer_size_kb", "16384");
151 SAFE_FILE_PRINTF(TRACING_DIR "set_event", TRACE_EVENTS);
152 SAFE_FILE_PRINTF(TRACING_DIR "trace", "\n");
153 SAFE_FILE_PRINTF(TRACING_DIR "tracing_on", "1");
154
155 SAFE_PTHREAD_CREATE(&task_thread, NULL, task_fn, NULL);
156 SAFE_PTHREAD_JOIN(task_thread, NULL);
157
158 /* disable tracing */
159 SAFE_FILE_PRINTF(TRACING_DIR "tracing_on", "0");
160 LOAD_TRACE();
161
162 if (parse_results())
163 tst_res(TFAIL, "Task placement/migration latency goals "
164 "not met.\n");
165 else
166 tst_res(TPASS, "Task placement/migration latency goals "
167 "met.\n");
168 }
169
170 static struct tst_test test = {
171 .test_all = run,
172 .cleanup = trace_cleanup,
173 };
174