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
handle_direct_reclaim_begin()30 static int handle_direct_reclaim_begin()
31 {
32 u64 *vm_zone_stat_kaddrp = (u64*)vm_zone_stat_kaddr;
33 u64 id = bpf_get_current_pid_tgid();
34 struct piddata piddata = {};
35 u32 tgid = id >> 32;
36 u32 pid = id;
37
38 if (targ_tgid && targ_tgid != tgid)
39 return 0;
40 if (targ_pid && targ_pid != pid)
41 return 0;
42
43 piddata.ts = bpf_ktime_get_ns();
44 if (vm_zone_stat_kaddrp) {
45 bpf_probe_read_kernel(&piddata.nr_free_pages,
46 sizeof(*vm_zone_stat_kaddrp),
47 &vm_zone_stat_kaddrp[NR_FREE_PAGES]);
48 }
49
50 bpf_map_update_elem(&start, &pid, &piddata, 0);
51 return 0;
52 }
53
handle_direct_reclaim_end(void * ctx,unsigned long nr_reclaimed)54 static int handle_direct_reclaim_end(void *ctx, unsigned long nr_reclaimed)
55 {
56 u64 id = bpf_get_current_pid_tgid();
57 struct piddata *piddatap;
58 struct event event = {};
59 u32 tgid = id >> 32;
60 u32 pid = id;
61 s64 delta_ns;
62
63 if (targ_tgid && targ_tgid != tgid)
64 return 0;
65 if (targ_pid && targ_pid != pid)
66 return 0;
67
68 /* fetch timestamp and calculate delta */
69 piddatap = bpf_map_lookup_elem(&start, &pid);
70 if (!piddatap)
71 return 0; /* missed entry */
72
73 delta_ns = bpf_ktime_get_ns() - piddatap->ts;
74 if (delta_ns < 0)
75 goto cleanup;
76
77 event.pid = pid;
78 event.nr_reclaimed = nr_reclaimed;
79 event.delta_ns = delta_ns;
80 event.nr_free_pages = piddatap->nr_free_pages;
81 bpf_get_current_comm(&event.task, TASK_COMM_LEN);
82
83 /* output */
84 bpf_perf_event_output(ctx, &events, BPF_F_CURRENT_CPU,
85 &event, sizeof(event));
86
87 cleanup:
88 bpf_map_delete_elem(&start, &pid);
89 return 0;
90 }
91
92 SEC("tp_btf/mm_vmscan_direct_reclaim_begin")
BPF_PROG(direct_reclaim_begin_btf)93 int BPF_PROG(direct_reclaim_begin_btf)
94 {
95 return handle_direct_reclaim_begin();
96 }
97
98 SEC("tp_btf/mm_vmscan_direct_reclaim_end")
BPF_PROG(direct_reclaim_end_btf,unsigned long nr_reclaimed)99 int BPF_PROG(direct_reclaim_end_btf, unsigned long nr_reclaimed)
100 {
101 return handle_direct_reclaim_end(ctx, nr_reclaimed);
102 }
103
104 SEC("raw_tp/mm_vmscan_direct_reclaim_begin")
BPF_PROG(direct_reclaim_begin)105 int BPF_PROG(direct_reclaim_begin)
106 {
107 return handle_direct_reclaim_begin();
108 }
109
110 SEC("raw_tp/mm_vmscan_direct_reclaim_end")
BPF_PROG(direct_reclaim_end,unsigned long nr_reclaimed)111 int BPF_PROG(direct_reclaim_end, unsigned long nr_reclaimed)
112 {
113 return handle_direct_reclaim_end(ctx, nr_reclaimed);
114 }
115
116 char LICENSE[] SEC("license") = "GPL";
117