1 // SPDX-License-Identifier: GPL-2.0
2 // Copyright (c) 2020 Wenbo Zhang
3 #include <vmlinux.h>
4 #include <bpf/bpf_helpers.h>
5 #include <bpf/bpf_tracing.h>
6 #include "drsnoop.h"
7
8 const volatile pid_t targ_pid = 0;
9 const volatile pid_t targ_tgid = 0;
10 const volatile __u64 vm_zone_stat_kaddr = 0;
11
12 struct piddata {
13 u64 ts;
14 u64 nr_free_pages;
15 };
16
17 struct {
18 __uint(type, BPF_MAP_TYPE_HASH);
19 __uint(max_entries, 8192);
20 __type(key, u32);
21 __type(value, struct piddata);
22 } start SEC(".maps");
23
24 struct {
25 __uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
26 __uint(key_size, sizeof(u32));
27 __uint(value_size, sizeof(u32));
28 } events SEC(".maps");
29
30 SEC("tp_btf/mm_vmscan_direct_reclaim_begin")
BPF_PROG(direct_reclaim_begin)31 int BPF_PROG(direct_reclaim_begin)
32 {
33 u64 *vm_zone_stat_kaddrp = (u64*)vm_zone_stat_kaddr;
34 u64 id = bpf_get_current_pid_tgid();
35 struct piddata piddata = {};
36 u32 tgid = id >> 32;
37 u32 pid = id;
38
39 if (targ_tgid && targ_tgid != tgid)
40 return 0;
41 if (targ_pid && targ_pid != pid)
42 return 0;
43
44 piddata.ts = bpf_ktime_get_ns();
45 if (vm_zone_stat_kaddrp) {
46 bpf_probe_read_kernel(&piddata.nr_free_pages,
47 sizeof(*vm_zone_stat_kaddrp),
48 &vm_zone_stat_kaddrp[NR_FREE_PAGES]);
49 }
50
51 bpf_map_update_elem(&start, &pid, &piddata, 0);
52 return 0;
53 }
54
55 SEC("tp_btf/mm_vmscan_direct_reclaim_end")
BPF_PROG(direct_reclaim_end,unsigned long nr_reclaimed)56 int BPF_PROG(direct_reclaim_end, unsigned long nr_reclaimed)
57 {
58 u64 id = bpf_get_current_pid_tgid();
59 struct piddata *piddatap;
60 struct event event = {};
61 u32 tgid = id >> 32;
62 u32 pid = id;
63 s64 delta_ns;
64
65 if (targ_tgid && targ_tgid != tgid)
66 return 0;
67 if (targ_pid && targ_pid != pid)
68 return 0;
69
70 /* fetch timestamp and calculate delta */
71 piddatap = bpf_map_lookup_elem(&start, &pid);
72 if (!piddatap)
73 return 0; /* missed entry */
74
75 delta_ns = bpf_ktime_get_ns() - piddatap->ts;
76 if (delta_ns < 0)
77 goto cleanup;
78
79 event.pid = pid;
80 event.nr_reclaimed = nr_reclaimed;
81 event.delta_ns = delta_ns;
82 event.nr_free_pages = piddatap->nr_free_pages;
83 bpf_get_current_comm(&event.task, TASK_COMM_LEN);
84
85 /* output */
86 bpf_perf_event_output(ctx, &events, BPF_F_CURRENT_CPU,
87 &event, sizeof(event));
88
89 cleanup:
90 bpf_map_delete_elem(&start, &pid);
91 return 0;
92 }
93
94 char LICENSE[] SEC("license") = "GPL";
95