1#!/usr/bin/env python3
2# SPDX-License-Identifier: LGPL-2.1-or-later
3
4import gdb
5
6class sd_dump_hashmaps(gdb.Command):
7    "dump systemd's hashmaps"
8
9    def __init__(self):
10        super().__init__("sd_dump_hashmaps", gdb.COMMAND_DATA, gdb.COMPLETE_NONE)
11
12    def invoke(self, arg, from_tty):
13        d = gdb.parse_and_eval("hashmap_debug_list")
14        hashmap_type_info = gdb.parse_and_eval("hashmap_type_info")
15        uchar_t = gdb.lookup_type("unsigned char")
16        ulong_t = gdb.lookup_type("unsigned long")
17        debug_offset = gdb.parse_and_eval("(unsigned long)&((HashmapBase*)0)->debug")
18
19        print("type, hash, indirect, entries, max_entries, buckets, creator")
20        while d:
21            h = gdb.parse_and_eval(f"(HashmapBase*)((char*){int(d.cast(ulong_t))} - {debug_offset})")
22
23            if h["has_indirect"]:
24                storage_ptr = h["indirect"]["storage"].cast(uchar_t.pointer())
25                n_entries = h["indirect"]["n_entries"]
26                n_buckets = h["indirect"]["n_buckets"]
27            else:
28                storage_ptr = h["direct"]["storage"].cast(uchar_t.pointer())
29                n_entries = h["n_direct_entries"]
30                n_buckets = hashmap_type_info[h["type"]]["n_direct_buckets"]
31
32            t = ["plain", "ordered", "set"][int(h["type"])]
33
34            print(f'{t}, {h["hash_ops"]}, {bool(h["has_indirect"])}, {n_entries}, {d["max_entries"]}, {n_buckets}, {d["func"].string()}, {d["file"].string()}:{d["line"]}')
35
36            if arg != "" and n_entries > 0:
37                dib_raw_addr = storage_ptr + hashmap_type_info[h["type"]]["entry_size"] * n_buckets
38
39                histogram = {}
40                for i in range(0, n_buckets):
41                    dib = int(dib_raw_addr[i])
42                    histogram[dib] = histogram.get(dib, 0) + 1
43
44                for dib in sorted(histogram):
45                    if dib != 255:
46                        print(f"{dib:>3} {histogram[dib]:>8} {float(histogram[dib]/n_entries):.0%} of entries")
47                    else:
48                        print(f"{dib:>3} {histogram[dib]:>8} {float(histogram[dib]/n_buckets):.0%} of slots")
49                        s = sum(dib*count for (dib, count) in histogram.items() if dib != 255) / n_entries
50                        print(f"mean DIB of entries: {s}")
51
52                blocks = []
53                current_len = 1
54                prev = int(dib_raw_addr[0])
55                for i in range(1, n_buckets):
56                    dib = int(dib_raw_addr[i])
57                    if (dib == 255) != (prev == 255):
58                        if prev != 255:
59                            blocks += [[i, current_len]]
60                            current_len = 1
61                    else:
62                        current_len += 1
63
64                    prev = dib
65                if prev != 255:
66                    blocks += [[i, current_len]]
67                    # a block may be wrapped around
68                if len(blocks) > 1 and blocks[0][0] == blocks[0][1] and blocks[-1][0] == n_buckets - 1:
69                    blocks[0][1] += blocks[-1][1]
70                    blocks = blocks[0:-1]
71                    print("max block: {}".format(max(blocks, key=lambda a: a[1])))
72                    print("sum block lens: {}".format(sum(b[1] for b in blocks)))
73                    print("mean block len: {}".format(sum(b[1] for b in blocks) / len(blocks)))
74
75            d = d["debug_list_next"]
76
77sd_dump_hashmaps()
78