Alexey Ivanov | cc01a9c | 2019-01-16 09:50:46 -0800 | [diff] [blame] | 1 | #!/usr/bin/python |
Brendan Gregg | 2757f0e | 2016-02-10 01:38:32 -0800 | [diff] [blame] | 2 | # @lint-avoid-python-3-compatibility-imports |
| 3 | # |
| 4 | # dcsnoop Trace directory entry cache (dcache) lookups. |
| 5 | # For Linux, uses BCC, eBPF. Embedded C. |
| 6 | # |
| 7 | # USAGE: dcsnoop [-h] [-a] |
| 8 | # |
| 9 | # By default, this traces every failed dcache lookup, and shows the process |
| 10 | # performing the lookup and the filename requested. A -a option can be used |
| 11 | # to show all lookups, not just failed ones. |
| 12 | # |
| 13 | # This uses kernel dynamic tracing of the d_lookup() function, and will need |
| 14 | # to be modified to match kernel changes. |
| 15 | # |
| 16 | # Also see dcstat(8), for per-second summaries. |
| 17 | # |
| 18 | # Copyright 2016 Netflix, Inc. |
| 19 | # Licensed under the Apache License, Version 2.0 (the "License") |
| 20 | # |
| 21 | # 09-Feb-2016 Brendan Gregg Created this. |
| 22 | |
| 23 | from __future__ import print_function |
| 24 | from bcc import BPF |
| 25 | import argparse |
| 26 | import re |
Mark Drayton | 44b4b5f | 2016-07-13 18:15:05 +0100 | [diff] [blame] | 27 | import time |
Brendan Gregg | 2757f0e | 2016-02-10 01:38:32 -0800 | [diff] [blame] | 28 | |
| 29 | # arguments |
| 30 | examples = """examples: |
| 31 | ./dcsnoop # trace failed dcache lookups |
| 32 | ./dcsnoop -a # trace all dcache lookups |
| 33 | """ |
| 34 | parser = argparse.ArgumentParser( |
| 35 | description="Trace directory entry cache (dcache) lookups", |
| 36 | formatter_class=argparse.RawDescriptionHelpFormatter, |
| 37 | epilog=examples) |
| 38 | parser.add_argument("-a", "--all", action="store_true", |
| 39 | help="trace all lookups (default is fails only)") |
Nathan Scott | cf0792f | 2018-02-02 16:56:50 +1100 | [diff] [blame] | 40 | parser.add_argument("--ebpf", action="store_true", |
| 41 | help=argparse.SUPPRESS) |
Brendan Gregg | 2757f0e | 2016-02-10 01:38:32 -0800 | [diff] [blame] | 42 | args = parser.parse_args() |
| 43 | |
| 44 | # define BPF program |
| 45 | bpf_text = """ |
| 46 | #include <uapi/linux/ptrace.h> |
| 47 | #include <linux/fs.h> |
| 48 | #include <linux/sched.h> |
| 49 | |
| 50 | #define MAX_FILE_LEN 64 |
| 51 | |
Mark Drayton | 44b4b5f | 2016-07-13 18:15:05 +0100 | [diff] [blame] | 52 | enum lookup_type { |
| 53 | LOOKUP_MISS, |
| 54 | LOOKUP_REFERENCE, |
| 55 | }; |
| 56 | |
Brendan Gregg | 2757f0e | 2016-02-10 01:38:32 -0800 | [diff] [blame] | 57 | struct entry_t { |
| 58 | char name[MAX_FILE_LEN]; |
| 59 | }; |
| 60 | |
| 61 | BPF_HASH(entrybypid, u32, struct entry_t); |
| 62 | |
Mark Drayton | 44b4b5f | 2016-07-13 18:15:05 +0100 | [diff] [blame] | 63 | struct data_t { |
| 64 | u32 pid; |
| 65 | enum lookup_type type; |
| 66 | char comm[TASK_COMM_LEN]; |
| 67 | char filename[MAX_FILE_LEN]; |
| 68 | }; |
| 69 | |
| 70 | BPF_PERF_OUTPUT(events); |
| 71 | |
Brendan Gregg | 2757f0e | 2016-02-10 01:38:32 -0800 | [diff] [blame] | 72 | /* from fs/namei.c: */ |
| 73 | struct nameidata { |
| 74 | struct path path; |
| 75 | struct qstr last; |
| 76 | // [...] |
| 77 | }; |
| 78 | |
Mark Drayton | 44b4b5f | 2016-07-13 18:15:05 +0100 | [diff] [blame] | 79 | static inline |
| 80 | void submit_event(struct pt_regs *ctx, void *name, int type, u32 pid) |
| 81 | { |
| 82 | struct data_t data = { |
| 83 | .pid = pid, |
| 84 | .type = type, |
| 85 | }; |
| 86 | bpf_get_current_comm(&data.comm, sizeof(data.comm)); |
Sumanth Korikkar | 7f6066d | 2020-05-20 10:49:56 -0500 | [diff] [blame] | 87 | bpf_probe_read_kernel(&data.filename, sizeof(data.filename), name); |
Mark Drayton | 44b4b5f | 2016-07-13 18:15:05 +0100 | [diff] [blame] | 88 | events.perf_submit(ctx, &data, sizeof(data)); |
| 89 | } |
| 90 | |
Brendan Gregg | 2757f0e | 2016-02-10 01:38:32 -0800 | [diff] [blame] | 91 | int trace_fast(struct pt_regs *ctx, struct nameidata *nd, struct path *path) |
| 92 | { |
Hengqi Chen | f0a0dc7 | 2021-05-20 22:49:25 +0800 | [diff] [blame] | 93 | u32 pid = bpf_get_current_pid_tgid() >> 32; |
Mark Drayton | 44b4b5f | 2016-07-13 18:15:05 +0100 | [diff] [blame] | 94 | submit_event(ctx, (void *)nd->last.name, LOOKUP_REFERENCE, pid); |
Brendan Gregg | 2757f0e | 2016-02-10 01:38:32 -0800 | [diff] [blame] | 95 | return 1; |
| 96 | } |
| 97 | |
| 98 | int kprobe__d_lookup(struct pt_regs *ctx, const struct dentry *parent, |
| 99 | const struct qstr *name) |
| 100 | { |
Hengqi Chen | f0a0dc7 | 2021-05-20 22:49:25 +0800 | [diff] [blame] | 101 | u32 tid = bpf_get_current_pid_tgid(); |
Brendan Gregg | 2757f0e | 2016-02-10 01:38:32 -0800 | [diff] [blame] | 102 | struct entry_t entry = {}; |
Brendan Gregg | d18657e | 2016-02-10 16:38:18 -0800 | [diff] [blame] | 103 | const char *fname = name->name; |
| 104 | if (fname) { |
Sumanth Korikkar | 7f6066d | 2020-05-20 10:49:56 -0500 | [diff] [blame] | 105 | bpf_probe_read_kernel(&entry.name, sizeof(entry.name), (void *)fname); |
Brendan Gregg | 2757f0e | 2016-02-10 01:38:32 -0800 | [diff] [blame] | 106 | } |
Hengqi Chen | f0a0dc7 | 2021-05-20 22:49:25 +0800 | [diff] [blame] | 107 | entrybypid.update(&tid, &entry); |
Brendan Gregg | 2757f0e | 2016-02-10 01:38:32 -0800 | [diff] [blame] | 108 | return 0; |
| 109 | } |
| 110 | |
| 111 | int kretprobe__d_lookup(struct pt_regs *ctx) |
| 112 | { |
Hengqi Chen | f0a0dc7 | 2021-05-20 22:49:25 +0800 | [diff] [blame] | 113 | u64 pid_tgid = bpf_get_current_pid_tgid(); |
| 114 | u32 pid = pid_tgid >> 32; |
| 115 | u32 tid = (u32)pid_tgid; |
Brendan Gregg | 2757f0e | 2016-02-10 01:38:32 -0800 | [diff] [blame] | 116 | struct entry_t *ep; |
Hengqi Chen | f0a0dc7 | 2021-05-20 22:49:25 +0800 | [diff] [blame] | 117 | |
| 118 | ep = entrybypid.lookup(&tid); |
| 119 | if (ep == 0) { |
| 120 | return 0; // missed entry |
Brendan Gregg | 2757f0e | 2016-02-10 01:38:32 -0800 | [diff] [blame] | 121 | } |
Hengqi Chen | f0a0dc7 | 2021-05-20 22:49:25 +0800 | [diff] [blame] | 122 | if (PT_REGS_RC(ctx) != 0) { |
| 123 | entrybypid.delete(&tid); |
| 124 | return 0; // lookup didn't fail |
| 125 | } |
| 126 | |
Mark Drayton | 44b4b5f | 2016-07-13 18:15:05 +0100 | [diff] [blame] | 127 | submit_event(ctx, (void *)ep->name, LOOKUP_MISS, pid); |
Hengqi Chen | f0a0dc7 | 2021-05-20 22:49:25 +0800 | [diff] [blame] | 128 | entrybypid.delete(&tid); |
Brendan Gregg | 2757f0e | 2016-02-10 01:38:32 -0800 | [diff] [blame] | 129 | return 0; |
| 130 | } |
| 131 | """ |
| 132 | |
Nathan Scott | cf0792f | 2018-02-02 16:56:50 +1100 | [diff] [blame] | 133 | if args.ebpf: |
| 134 | print(bpf_text) |
| 135 | exit() |
| 136 | |
Brendan Gregg | 2757f0e | 2016-02-10 01:38:32 -0800 | [diff] [blame] | 137 | # initialize BPF |
| 138 | b = BPF(text=bpf_text) |
| 139 | if args.all: |
Jerome Marchand | cdfddc4 | 2021-03-20 14:33:59 +0100 | [diff] [blame] | 140 | b.attach_kprobe(event_re="^lookup_fast$|^lookup_fast.constprop.*.\d$", fn_name="trace_fast") |
Brendan Gregg | 2757f0e | 2016-02-10 01:38:32 -0800 | [diff] [blame] | 141 | |
Mark Drayton | 44b4b5f | 2016-07-13 18:15:05 +0100 | [diff] [blame] | 142 | mode_s = { |
| 143 | 0: 'M', |
| 144 | 1: 'R', |
| 145 | } |
| 146 | |
| 147 | start_ts = time.time() |
| 148 | |
| 149 | def print_event(cpu, data, size): |
Xiaozhou Liu | 6c79c68 | 2019-02-15 03:41:22 +0800 | [diff] [blame] | 150 | event = b["events"].event(data) |
xingfeng2510 | 03e4948 | 2022-03-17 13:07:16 +0800 | [diff] [blame] | 151 | print("%-11.6f %-7d %-16s %1s %s" % ( |
jeromemarchand | b96ebcd | 2018-10-10 01:58:15 +0200 | [diff] [blame] | 152 | time.time() - start_ts, event.pid, |
| 153 | event.comm.decode('utf-8', 'replace'), mode_s[event.type], |
| 154 | event.filename.decode('utf-8', 'replace'))) |
Mark Drayton | 44b4b5f | 2016-07-13 18:15:05 +0100 | [diff] [blame] | 155 | |
Brendan Gregg | 2757f0e | 2016-02-10 01:38:32 -0800 | [diff] [blame] | 156 | # header |
xingfeng2510 | 03e4948 | 2022-03-17 13:07:16 +0800 | [diff] [blame] | 157 | print("%-11s %-7s %-16s %1s %s" % ("TIME(s)", "PID", "COMM", "T", "FILE")) |
Brendan Gregg | 2757f0e | 2016-02-10 01:38:32 -0800 | [diff] [blame] | 158 | |
Mark Drayton | 5f5687e | 2017-02-20 18:13:03 +0000 | [diff] [blame] | 159 | b["events"].open_perf_buffer(print_event, page_cnt=64) |
Brendan Gregg | 2757f0e | 2016-02-10 01:38:32 -0800 | [diff] [blame] | 160 | while 1: |
Jerome Marchand | 5167127 | 2018-12-19 01:57:24 +0100 | [diff] [blame] | 161 | try: |
| 162 | b.perf_buffer_poll() |
| 163 | except KeyboardInterrupt: |
| 164 | exit() |