tools/gdb-sd_dump_hashmaps.py

   1 #!/usr/bin/env python3
   2 # SPDX-License-Identifier: LGPL-2.1+
   3
   4 import gdb
   5
   6 class 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
  77 sd_dump_hashmaps()