Inside Bitcoin

1#!/usr/bin/env python3
2# Copyright (c) 2021-present The Bitcoin Core developers
3# Distributed under the MIT software license, see the accompanying
4# file COPYING or http://www.opensource.org/licenses/mit-license.php.
5
6import sys
7import ctypes
8from bcc import BPF, USDT
9
10"""Example logging Bitcoin Core utxo set cache flushes utilizing
11    the utxocache:flush tracepoint."""
12
13# USAGE:  ./contrib/tracing/log_utxocache_flush.py <pid of bitcoind>
14
15# BCC: The C program to be compiled to an eBPF program (by BCC) and loaded into
16# a sandboxed Linux kernel VM.
17program = """
18# include <uapi/linux/ptrace.h>
19
20struct data_t
21{
22  u64 duration;
23  u32 mode;
24  u64 coins_count;
25  u64 coins_mem_usage;
26  bool is_flush_for_prune;
27};
28
29// BPF perf buffer to push the data to user space.
30BPF_PERF_OUTPUT(flush);
31
32int trace_flush(struct pt_regs *ctx) {
33  struct data_t data = {};
34  bpf_usdt_readarg(1, ctx, &data.duration);
35  bpf_usdt_readarg(2, ctx, &data.mode);
36  bpf_usdt_readarg(3, ctx, &data.coins_count);
37  bpf_usdt_readarg(4, ctx, &data.coins_mem_usage);
38  bpf_usdt_readarg(5, ctx, &data.is_flush_for_prune);
39  flush.perf_submit(ctx, &data, sizeof(data));
40  return 0;
41}
42"""
43
44FLUSH_MODES = [
45    'NONE',
46    'IF_NEEDED',
47    'PERIODIC',
48    'FORCE_FLUSH',
49    'FORCE_SYNC',
50]
51
52
53class Data(ctypes.Structure):
54    # define output data structure corresponding to struct data_t
55    _fields_ = [
56        ("duration", ctypes.c_uint64),
57        ("mode", ctypes.c_uint32),
58        ("coins_count", ctypes.c_uint64),
59        ("coins_mem_usage", ctypes.c_uint64),
60        ("is_flush_for_prune", ctypes.c_bool)
61    ]
62
63
64def print_event(event):
65    print("%-15d %-12s %-15d %-15s %-8s" % (
66        event.duration,
67        FLUSH_MODES[event.mode],
68        event.coins_count,
69        "%.2f kB" % (event.coins_mem_usage/1000),
70        event.is_flush_for_prune
71    ))
72
73
74def main(pid):
75    print(f"Hooking into bitcoind with pid {pid}")
76    bitcoind_with_usdts = USDT(pid=int(pid))
77
78    # attaching the trace functions defined in the BPF program
79    # to the tracepoints
80    bitcoind_with_usdts.enable_probe(
81        probe="flush", fn_name="trace_flush")
82    b = BPF(text=program, usdt_contexts=[bitcoind_with_usdts])
83
84    def handle_flush(_, data, size):
85        """ Coins Flush handler.
86          Called each time coin caches and indexes are flushed."""
87        event = ctypes.cast(data, ctypes.POINTER(Data)).contents
88        print_event(event)
89
90    b["flush"].open_perf_buffer(handle_flush)
91    print("Logging utxocache flushes. Ctrl-C to end...")
92    print("%-15s %-12s %-15s %-15s %-8s" % ("Duration (µs)", "Mode",
93                                            "Coins Count", "Memory Usage",
94                                            "Flush for Prune"))
95
96    while True:
97        try:
98            b.perf_buffer_poll()
99        except KeyboardInterrupt:
100            exit(0)
101
102
103if __name__ == "__main__":
104    if len(sys.argv) != 2:
105        print("USAGE: ", sys.argv[0], "<pid of bitcoind>")
106        exit(1)
107
108    pid = sys.argv[1]
109    main(pid)
110