fix: BTreeMap memory issue when deallocating nodes with overflows

[ielashi]

Problem

When storing unbounded types in a BTreeMap, a node is represented as a linked list of "memory chunks". It was discovered recently that when we deallocate a node, in some cases only the first memory chunk is deallocated, and the rest of the memory chunks remain (incorrectly) allocated, causing a memory issue.

Solution

Change the logic for deallocating nodes to ensure that all of a node's memory chunks are deallocated. Tests have been added to prevent regressions of this nature moving forward.

[github-actions]

canbench 🏋 (dir: .)

No significant performance changes detected ✅

./canbench_results.yml is up to date ✅

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Benchmark: btreemap_insert_blob_4_1024
  total:
    instructions: 601.82 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 123 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_blob_4_1024_v2
  total:
    instructions: 685.72 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 92 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_blob_8_1024
  total:
    instructions: 720.47 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 183 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_blob_8_1024_v2
  total:
    instructions: 811.30 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 138 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_blob_16_1024
  total:
    instructions: 802.98 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 215 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_blob_16_1024_v2
  total:
    instructions: 900.36 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 161 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_blob_32_1024
  total:
    instructions: 852.44 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 230 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_blob_32_1024_v2
  total:
    instructions: 944.16 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 173 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_blob_64_1024
  total:
    instructions: 1.12 B (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 245 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_blob_64_1024_v2
  total:
    instructions: 1.22 B (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 183 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_blob_128_1024
  total:
    instructions: 1.38 B (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 260 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_blob_128_1024_v2
  total:
    instructions: 1.51 B (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 195 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_blob_256_1024
  total:
    instructions: 1.91 B (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 292 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_blob_256_1024_v2
  total:
    instructions: 2.10 B (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 219 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_blob_512_1024
  total:
    instructions: 2.99 B (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 351 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_blob_512_1024_v2
  total:
    instructions: 3.24 B (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 263 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_blob_1024_4
  total:
    instructions: 4.79 B (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 235 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_blob_1024_4_v2
  total:
    instructions: 5.19 B (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 176 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_blob_1024_8
  total:
    instructions: 4.88 B (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 237 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_blob_1024_8_v2
  total:
    instructions: 5.27 B (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 178 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_blob_1024_16
  total:
    instructions: 4.89 B (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 241 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_blob_1024_16_v2
  total:
    instructions: 5.28 B (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 181 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_blob_1024_32
  total:
    instructions: 4.91 B (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 239 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_blob_1024_32_v2
  total:
    instructions: 5.30 B (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 180 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_blob_1024_64
  total:
    instructions: 4.93 B (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 250 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_blob_1024_64_v2
  total:
    instructions: 5.32 B (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 188 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_blob_1024_128
  total:
    instructions: 4.93 B (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 262 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_blob_1024_128_v2
  total:
    instructions: 5.32 B (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 196 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_blob_1024_256
  total:
    instructions: 4.94 B (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 292 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_blob_1024_256_v2
  total:
    instructions: 5.33 B (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 219 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_blob_1024_512
  total:
    instructions: 5.03 B (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 348 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_blob_1024_512_v2
  total:
    instructions: 5.43 B (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 261 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_u64_u64
  total:
    instructions: 438.06 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 7 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_u64_u64_v2
  total:
    instructions: 508.14 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 6 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_u64_blob_8
  total:
    instructions: 426.45 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 7 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_u64_blob_8_v2
  total:
    instructions: 492.82 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 5 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_blob_8_u64
  total:
    instructions: 416.17 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 6 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_blob_8_u64_v2
  total:
    instructions: 514.62 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 4 pages (no change)

---------------------------------------------------

Benchmark: btreemap_insert_10mib_values
  total:
    instructions: 99.51 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 32 pages (no change)

---------------------------------------------------

Benchmark: btreemap_iter_count_small_values
  total:
    instructions: 10.12 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_iter_count_10mib_values
  total:
    instructions: 497.38 K (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_remove_blob_4_1024
  total:
    instructions: 617.06 M (0.08%) (change within noise threshold)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_remove_blob_4_1024_v2
  total:
    instructions: 717.02 M (0.07%) (change within noise threshold)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_remove_blob_8_1024
  total:
    instructions: 806.03 M (0.08%) (change within noise threshold)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_remove_blob_8_1024_v2
  total:
    instructions: 921.72 M (0.06%) (change within noise threshold)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_remove_blob_16_1024
  total:
    instructions: 994.82 M (0.08%) (change within noise threshold)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_remove_blob_16_1024_v2
  total:
    instructions: 1.13 B (0.06%) (change within noise threshold)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_remove_blob_32_1024
  total:
    instructions: 1.07 B (0.10%) (change within noise threshold)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_remove_blob_32_1024_v2
  total:
    instructions: 1.20 B (0.09%) (change within noise threshold)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_remove_blob_64_1024
  total:
    instructions: 1.38 B (0.07%) (change within noise threshold)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_remove_blob_64_1024_v2
  total:
    instructions: 1.52 B (0.07%) (change within noise threshold)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_remove_blob_128_1024
  total:
    instructions: 1.69 B (0.06%) (change within noise threshold)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_remove_blob_128_1024_v2
  total:
    instructions: 1.84 B (0.06%) (change within noise threshold)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_remove_blob_256_1024
  total:
    instructions: 2.31 B (0.04%) (change within noise threshold)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_remove_blob_256_1024_v2
  total:
    instructions: 2.46 B (0.04%) (change within noise threshold)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_remove_blob_512_1024
  total:
    instructions: 3.60 B (0.02%) (change within noise threshold)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_remove_blob_512_1024_v2
  total:
    instructions: 3.75 B (0.02%) (change within noise threshold)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_remove_u64_u64
  total:
    instructions: 620.16 M (-0.07%) (change within noise threshold)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_remove_u64_u64_v2
  total:
    instructions: 725.33 M (-0.04%) (change within noise threshold)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_remove_u64_blob_8
  total:
    instructions: 596.70 M (-0.05%) (change within noise threshold)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_remove_u64_blob_8_v2
  total:
    instructions: 692.85 M (-0.05%) (change within noise threshold)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_remove_blob_8_u64
  total:
    instructions: 538.41 M (-0.06%) (change within noise threshold)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_remove_blob_8_u64_v2
  total:
    instructions: 672.37 M (-0.05%) (change within noise threshold)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_get_blob_4_1024
  total:
    instructions: 242.79 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_get_blob_4_1024_v2
  total:
    instructions: 324.66 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_get_blob_8_1024
  total:
    instructions: 282.19 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_get_blob_8_1024_v2
  total:
    instructions: 363.31 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_get_blob_16_1024
  total:
    instructions: 361.11 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_get_blob_16_1024_v2
  total:
    instructions: 445.04 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_get_blob_32_1024
  total:
    instructions: 405.06 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_get_blob_32_1024_v2
  total:
    instructions: 488.78 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_get_blob_64_1024
  total:
    instructions: 649.03 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_get_blob_64_1024_v2
  total:
    instructions: 732.96 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_get_blob_128_1024
  total:
    instructions: 878.06 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_get_blob_128_1024_v2
  total:
    instructions: 976.05 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_get_blob_256_1024
  total:
    instructions: 1.38 B (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_get_blob_256_1024_v2
  total:
    instructions: 1.48 B (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_get_blob_512_1024
  total:
    instructions: 2.37 B (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_get_blob_512_1024_v2
  total:
    instructions: 2.47 B (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_get_u64_u64
  total:
    instructions: 234.87 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_get_u64_u64_v2
  total:
    instructions: 298.87 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_get_u64_blob_8
  total:
    instructions: 232.00 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_get_u64_blob_8_v2
  total:
    instructions: 290.96 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_get_blob_8_u64
  total:
    instructions: 252.25 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap_get_blob_8_u64_v2
  total:
    instructions: 334.30 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: vec_insert_blob_4
  total:
    instructions: 3.78 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: vec_insert_blob_8
  total:
    instructions: 3.78 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 1 pages (no change)

---------------------------------------------------

Benchmark: vec_insert_blob_16
  total:
    instructions: 3.78 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 2 pages (no change)

---------------------------------------------------

Benchmark: vec_insert_blob_32
  total:
    instructions: 3.78 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 5 pages (no change)

---------------------------------------------------

Benchmark: vec_insert_blob_64
  total:
    instructions: 3.78 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 9 pages (no change)

---------------------------------------------------

Benchmark: vec_insert_blob_128
  total:
    instructions: 3.78 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 19 pages (no change)

---------------------------------------------------

Benchmark: vec_insert_u64
  total:
    instructions: 5.85 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 1 pages (no change)

---------------------------------------------------

Benchmark: vec_get_blob_4
  total:
    instructions: 5.79 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: vec_get_blob_8
  total:
    instructions: 7.03 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: vec_get_blob_16
  total:
    instructions: 9.79 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: vec_get_blob_32
  total:
    instructions: 10.62 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: vec_get_blob_64
  total:
    instructions: 15.31 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: vec_get_blob_128
  total:
    instructions: 20.90 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: vec_get_u64
  total:
    instructions: 6.27 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: memory_manager_baseline
  total:
    instructions: 1052 (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 8000 pages (no change)

---------------------------------------------------

Benchmark: memory_manager_overhead
  total:
    instructions: 4.55 M (0.03%) (change within noise threshold)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 8320 pages (no change)

---------------------------------------------------

Benchmark: memory_manager_grow
  total:
    instructions: 286.25 M (0.34%) (change within noise threshold)
    heap_increase: 2 pages (no change)
    stable_memory_increase: 32.00 K pages (no change)

---------------------------------------------------

[dsarlis]

Did you also consider extending some of the benchmarks we have to ensure that we don't see any increase in stable memory usage during a remove operation?

[ielashi]

Did you also consider extending some of the benchmarks we have to ensure that we don't see any increase in stable memory usage during a remove operation?

In the current implementation we do increase stable memory in some cases on remove. This PR does not address that, and strictly speaking it's not a bug. I'll be looking into how/whether we can avoid that, but for now I'm prioritizing resolving the memory leak.