Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
1// SPDX-License-Identifier: GPL-2.0
2#include <linux/bpf.h>
3#include <bpf/bpf_tracing.h>
4#include <stdbool.h>
5#include "timerlat_bpf.h"
6
7#define nosubprog __always_inline
8#define MAX_ENTRIES_DEFAULT 4096
9
10char LICENSE[] SEC("license") = "GPL";
11
12struct trace_event_raw_timerlat_sample {
13 unsigned long long timer_latency;
14 int context;
15} __attribute__((preserve_access_index));
16
17struct {
18 __uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
19 __uint(max_entries, MAX_ENTRIES_DEFAULT);
20 __type(key, unsigned int);
21 __type(value, unsigned long long);
22} hist_irq SEC(".maps"), hist_thread SEC(".maps"), hist_user SEC(".maps");
23
24struct {
25 __uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
26 __uint(max_entries, SUMMARY_FIELD_N);
27 __type(key, unsigned int);
28 __type(value, unsigned long long);
29} summary_irq SEC(".maps"), summary_thread SEC(".maps"), summary_user SEC(".maps");
30
31struct {
32 __uint(type, BPF_MAP_TYPE_ARRAY);
33 __uint(max_entries, 1);
34 __type(key, unsigned int);
35 __type(value, unsigned long long);
36} stop_tracing SEC(".maps");
37
38struct {
39 __uint(type, BPF_MAP_TYPE_RINGBUF);
40 __uint(max_entries, 1);
41} signal_stop_tracing SEC(".maps");
42
43/* Params to be set by rtla */
44const volatile int bucket_size = 1;
45const volatile int output_divisor = 1000;
46const volatile int entries = 256;
47const volatile int irq_threshold;
48const volatile int thread_threshold;
49const volatile bool aa_only;
50
51nosubprog unsigned long long map_get(void *map,
52 unsigned int key)
53{
54 unsigned long long *value_ptr;
55
56 value_ptr = bpf_map_lookup_elem(map, &key);
57
58 return !value_ptr ? 0 : *value_ptr;
59}
60
61nosubprog void map_set(void *map,
62 unsigned int key,
63 unsigned long long value)
64{
65 bpf_map_update_elem(map, &key, &value, BPF_ANY);
66}
67
68nosubprog void map_increment(void *map,
69 unsigned int key)
70{
71 map_set(map, key, map_get(map, key) + 1);
72}
73
74nosubprog void update_main_hist(void *map,
75 int bucket)
76{
77 if (entries == 0)
78 /* No histogram */
79 return;
80
81 if (bucket >= entries)
82 /* Overflow */
83 return;
84
85 map_increment(map, bucket);
86}
87
88nosubprog void update_summary(void *map,
89 unsigned long long latency,
90 int bucket)
91{
92 if (aa_only)
93 /* Auto-analysis only, nothing to be done here */
94 return;
95
96 map_set(map, SUMMARY_CURRENT, latency);
97
98 if (bucket >= entries)
99 /* Overflow */
100 map_increment(map, SUMMARY_OVERFLOW);
101
102 if (latency > map_get(map, SUMMARY_MAX))
103 map_set(map, SUMMARY_MAX, latency);
104
105 if (latency < map_get(map, SUMMARY_MIN) || map_get(map, SUMMARY_COUNT) == 0)
106 map_set(map, SUMMARY_MIN, latency);
107
108 map_increment(map, SUMMARY_COUNT);
109 map_set(map, SUMMARY_SUM, map_get(map, SUMMARY_SUM) + latency);
110}
111
112nosubprog void set_stop_tracing(void)
113{
114 int value = 0;
115
116 /* Suppress further sample processing */
117 map_set(&stop_tracing, 0, 1);
118
119 /* Signal to userspace */
120 bpf_ringbuf_output(&signal_stop_tracing, &value, sizeof(value), 0);
121}
122
123SEC("tp/osnoise/timerlat_sample")
124int handle_timerlat_sample(struct trace_event_raw_timerlat_sample *tp_args)
125{
126 unsigned long long latency, latency_us;
127 int bucket;
128
129 if (map_get(&stop_tracing, 0))
130 return 0;
131
132 latency = tp_args->timer_latency / output_divisor;
133 latency_us = tp_args->timer_latency / 1000;
134 bucket = latency / bucket_size;
135
136 if (tp_args->context == 0) {
137 update_main_hist(&hist_irq, bucket);
138 update_summary(&summary_irq, latency, bucket);
139
140 if (irq_threshold != 0 && latency_us >= irq_threshold)
141 set_stop_tracing();
142 } else if (tp_args->context == 1) {
143 update_main_hist(&hist_thread, bucket);
144 update_summary(&summary_thread, latency, bucket);
145
146 if (thread_threshold != 0 && latency_us >= thread_threshold)
147 set_stop_tracing();
148 } else {
149 update_main_hist(&hist_user, bucket);
150 update_summary(&summary_user, latency, bucket);
151 }
152
153 return 0;
154}