1 files changed, 78 insertions, 0 deletions
diff --git a/tools/gdb-sd_dump_hashmaps.py b/tools/gdb-sd_dump_hashmaps.py
new file mode 100644
index 0000000..57f825a
--- /dev/null
+++ b/tools/gdb-sd_dump_hashmaps.py
@@ -0,0 +1,78 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: LGPL-2.1-or-later
+# pylint: disable=consider-using-f-string
+
+import gdb
+
+class sd_dump_hashmaps(gdb.Command):
+    "dump systemd's hashmaps"
+
+    def __init__(self):
+        super().__init__("sd_dump_hashmaps", gdb.COMMAND_DATA, gdb.COMPLETE_NONE)
+
+    def invoke(self, arg, _from_tty):
+        d = gdb.parse_and_eval("hashmap_debug_list")
+        hashmap_type_info = gdb.parse_and_eval("hashmap_type_info")
+        uchar_t = gdb.lookup_type("unsigned char")
+        ulong_t = gdb.lookup_type("unsigned long")
+        debug_offset = gdb.parse_and_eval("(unsigned long)&((HashmapBase*)0)->debug")
+
+        print("type, hash, indirect, entries, max_entries, buckets, creator")
+        while d:
+            h = gdb.parse_and_eval(f"(HashmapBase*)((char*){int(d.cast(ulong_t))} - {debug_offset})")
+
+            if h["has_indirect"]:
+                storage_ptr = h["indirect"]["storage"].cast(uchar_t.pointer())
+                n_entries = h["indirect"]["n_entries"]
+                n_buckets = h["indirect"]["n_buckets"]
+            else:
+                storage_ptr = h["direct"]["storage"].cast(uchar_t.pointer())
+                n_entries = h["n_direct_entries"]
+                n_buckets = hashmap_type_info[h["type"]]["n_direct_buckets"]
+
+            t = ["plain", "ordered", "set"][int(h["type"])]
+
+            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"]}')
+
+            if arg != "" and n_entries > 0:
+                dib_raw_addr = storage_ptr + hashmap_type_info[h["type"]]["entry_size"] * n_buckets
+
+                histogram = {}
+                for i in range(0, n_buckets):
+                    dib = int(dib_raw_addr[i])
+                    histogram[dib] = histogram.get(dib, 0) + 1
+
+                for dib in sorted(histogram):
+                    if dib != 255:
+                        print(f"{dib:>3} {histogram[dib]:>8} {float(histogram[dib]/n_entries):.0%} of entries")
+                    else:
+                        print(f"{dib:>3} {histogram[dib]:>8} {float(histogram[dib]/n_buckets):.0%} of slots")
+                        s = sum(dib*count for (dib, count) in histogram.items() if dib != 255) / n_entries
+                        print(f"mean DIB of entries: {s}")
+
+                blocks = []
+                current_len = 1
+                prev = int(dib_raw_addr[0])
+                for i in range(1, n_buckets):
+                    dib = int(dib_raw_addr[i])
+                    if (dib == 255) != (prev == 255):
+                        if prev != 255:
+                            blocks += [[i, current_len]]
+                            current_len = 1
+                    else:
+                        current_len += 1
+
+                    prev = dib
+                if prev != 255:
+                    blocks += [[i, current_len]]
+                    # a block may be wrapped around
+                if len(blocks) > 1 and blocks[0][0] == blocks[0][1] and blocks[-1][0] == n_buckets - 1:
+                    blocks[0][1] += blocks[-1][1]
+                    blocks = blocks[0:-1]
+                    print("max block: {}".format(max(blocks, key=lambda a: a[1])))
+                    print("sum block lens: {}".format(sum(b[1] for b in blocks)))
+                    print("mean block len: {}".format(sum(b[1] for b in blocks) / len(blocks)))
+
+            d = d["debug_list_next"]
+
+sd_dump_hashmaps()