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
|
// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
// Copyright (c) 2022 Google
#include "vmlinux.h"
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>
#include <bpf/bpf_core_read.h>
/* task->flags for off-cpu analysis */
#define PF_KTHREAD 0x00200000 /* I am a kernel thread */
/* task->state for off-cpu analysis */
#define TASK_INTERRUPTIBLE 0x0001
#define TASK_UNINTERRUPTIBLE 0x0002
#define MAX_STACKS 32
#define MAX_ENTRIES 102400
struct tstamp_data {
__u32 stack_id;
__u32 state;
__u64 timestamp;
};
struct offcpu_key {
__u32 pid;
__u32 tgid;
__u32 stack_id;
__u32 state;
};
struct {
__uint(type, BPF_MAP_TYPE_STACK_TRACE);
__uint(key_size, sizeof(__u32));
__uint(value_size, MAX_STACKS * sizeof(__u64));
__uint(max_entries, MAX_ENTRIES);
} stacks SEC(".maps");
struct {
__uint(type, BPF_MAP_TYPE_TASK_STORAGE);
__uint(map_flags, BPF_F_NO_PREALLOC);
__type(key, int);
__type(value, struct tstamp_data);
} tstamp SEC(".maps");
struct {
__uint(type, BPF_MAP_TYPE_HASH);
__uint(key_size, sizeof(struct offcpu_key));
__uint(value_size, sizeof(__u64));
__uint(max_entries, MAX_ENTRIES);
} off_cpu SEC(".maps");
struct {
__uint(type, BPF_MAP_TYPE_HASH);
__uint(key_size, sizeof(__u32));
__uint(value_size, sizeof(__u8));
__uint(max_entries, 1);
} cpu_filter SEC(".maps");
struct {
__uint(type, BPF_MAP_TYPE_HASH);
__uint(key_size, sizeof(__u32));
__uint(value_size, sizeof(__u8));
__uint(max_entries, 1);
} task_filter SEC(".maps");
/* old kernel task_struct definition */
struct task_struct___old {
long state;
} __attribute__((preserve_access_index));
int enabled = 0;
int has_cpu = 0;
int has_task = 0;
const volatile bool has_prev_state = false;
/*
* Old kernel used to call it task_struct->state and now it's '__state'.
* Use BPF CO-RE "ignored suffix rule" to deal with it like below:
*
* https://nakryiko.com/posts/bpf-core-reference-guide/#handling-incompatible-field-and-type-changes
*/
static inline int get_task_state(struct task_struct *t)
{
if (bpf_core_field_exists(t->__state))
return BPF_CORE_READ(t, __state);
/* recast pointer to capture task_struct___old type for compiler */
struct task_struct___old *t_old = (void *)t;
/* now use old "state" name of the field */
return BPF_CORE_READ(t_old, state);
}
static inline int can_record(struct task_struct *t, int state)
{
/* kernel threads don't have user stack */
if (t->flags & PF_KTHREAD)
return 0;
if (state != TASK_INTERRUPTIBLE &&
state != TASK_UNINTERRUPTIBLE)
return 0;
if (has_cpu) {
__u32 cpu = bpf_get_smp_processor_id();
__u8 *ok;
ok = bpf_map_lookup_elem(&cpu_filter, &cpu);
if (!ok)
return 0;
}
if (has_task) {
__u8 *ok;
__u32 pid = t->pid;
ok = bpf_map_lookup_elem(&task_filter, &pid);
if (!ok)
return 0;
}
return 1;
}
static int off_cpu_stat(u64 *ctx, struct task_struct *prev,
struct task_struct *next, int state)
{
__u64 ts;
__u32 stack_id;
struct tstamp_data *pelem;
ts = bpf_ktime_get_ns();
if (!can_record(prev, state))
goto next;
stack_id = bpf_get_stackid(ctx, &stacks,
BPF_F_FAST_STACK_CMP | BPF_F_USER_STACK);
pelem = bpf_task_storage_get(&tstamp, prev, NULL,
BPF_LOCAL_STORAGE_GET_F_CREATE);
if (!pelem)
goto next;
pelem->timestamp = ts;
pelem->state = state;
pelem->stack_id = stack_id;
next:
pelem = bpf_task_storage_get(&tstamp, next, NULL, 0);
if (pelem && pelem->timestamp) {
struct offcpu_key key = {
.pid = next->pid,
.tgid = next->tgid,
.stack_id = pelem->stack_id,
.state = pelem->state,
};
__u64 delta = ts - pelem->timestamp;
__u64 *total;
total = bpf_map_lookup_elem(&off_cpu, &key);
if (total)
*total += delta;
else
bpf_map_update_elem(&off_cpu, &key, &delta, BPF_ANY);
/* prevent to reuse the timestamp later */
pelem->timestamp = 0;
}
return 0;
}
SEC("tp_btf/sched_switch")
int on_switch(u64 *ctx)
{
struct task_struct *prev, *next;
int prev_state;
if (!enabled)
return 0;
prev = (struct task_struct *)ctx[1];
next = (struct task_struct *)ctx[2];
if (has_prev_state)
prev_state = (int)ctx[3];
else
prev_state = get_task_state(prev);
return off_cpu_stat(ctx, prev, next, prev_state);
}
char LICENSE[] SEC("license") = "Dual BSD/GPL";
|
