feat: add manual bucket release to prevent memory waste #386

maksymar · 2025-08-15T11:20:28Z

This PR adds release_virtual_memory_buckets() to enable manual bucket reclamation when stable structures (BTreeMap, Vec) are cleared.

Problem: Stable structures and MemoryManager operate independently - the memory manager allocates buckets but doesn't know when structures are cleared. When migrating data (A→B), clearing structure A doesn't automatically release its memory buckets, preventing structure B from reusing them and causing memory waste.

Solution: After clearing a stable structure, manually call release_virtual_memory_buckets(memory_id) to release its buckets for reuse by other structures.

Safety: Users must ensure the structure is fully cleared before releasing buckets. The memory manager provides no safety checks - releasing active buckets causes memory corruption.

Includes comprehensive tests demonstrating migration scenarios and verifying correct implementation.

github-actions · 2025-08-15T11:33:01Z

`canbench` 🏋 (dir: ./benchmarks/nns) `63579e8` 2025-08-16 09:14:25 UTC

✅ ./benchmarks/nns/canbench_results.yml is up to date
📦 canbench_results_nns.csv available in artifacts

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

Summary:
  instructions:
    status:   No significant changes 👍
    counts:   [total 16 | regressed 0 | improved 0 | new 0 | unchanged 16]
    change:   [max 0 | p75 0 | median -98 | p25 -439.05K | min -6.98M]
    change %: [max 0.00% | p75 0.00% | median -0.04% | p25 -0.16% | min -0.29%]

  heap_increase:
    status:   No significant changes 👍
    counts:   [total 16 | regressed 0 | improved 0 | new 0 | unchanged 16]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

  stable_memory_increase:
    status:   No significant changes 👍
    counts:   [total 16 | regressed 0 | improved 0 | new 0 | unchanged 16]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

---------------------------------------------------
CSV results saved to canbench_results.csv

github-actions · 2025-08-15T11:33:02Z

`canbench` 🏋 (dir: ./benchmarks/btreemap) `63579e8` 2025-08-16 09:15:56 UTC

✅ ./benchmarks/btreemap/canbench_results.yml is up to date
📦 canbench_results_btreemap.csv available in artifacts

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

Summary:
  instructions:
    status:   No significant changes 👍
    counts:   [total 303 | regressed 0 | improved 0 | new 0 | unchanged 303]
    change:   [max +188.14K | p75 0 | median -3.78K | p25 -4.03K | min -1.55M]
    change %: [max +0.02% | p75 0.00% | median -0.00% | p25 -0.00% | min -0.03%]

  heap_increase:
    status:   No significant changes 👍
    counts:   [total 303 | regressed 0 | improved 0 | new 0 | unchanged 303]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

  stable_memory_increase:
    status:   No significant changes 👍
    counts:   [total 303 | regressed 0 | improved 0 | new 0 | unchanged 303]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

---------------------------------------------------
CSV results saved to canbench_results.csv

github-actions · 2025-08-15T11:33:02Z

`canbench` 🏋 (dir: ./benchmarks/btreeset) `63579e8` 2025-08-16 09:14:27 UTC

✅ ./benchmarks/btreeset/canbench_results.yml is up to date
📦 canbench_results_btreeset.csv available in artifacts

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

Summary:
  instructions:
    status:   No significant changes 👍
    counts:   [total 100 | regressed 0 | improved 0 | new 0 | unchanged 100]
    change:   [max +1.32K | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

  heap_increase:
    status:   No significant changes 👍
    counts:   [total 100 | regressed 0 | improved 0 | new 0 | unchanged 100]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

  stable_memory_increase:
    status:   No significant changes 👍
    counts:   [total 100 | regressed 0 | improved 0 | new 0 | unchanged 100]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

---------------------------------------------------
CSV results saved to canbench_results.csv

github-actions · 2025-08-15T11:33:02Z

`canbench` 🏋 (dir: ./benchmarks/memory_manager) `63579e8` 2025-08-16 09:14:23 UTC

✅ ./benchmarks/memory_manager/canbench_results.yml is up to date
📦 canbench_results_memory-manager.csv available in artifacts

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

Summary:
  instructions:
    status:   No significant changes 👍
    counts:   [total 3 | regressed 0 | improved 0 | new 0 | unchanged 3]
    change:   [max +768.00K | p75 +388.04K | median +8.09K | p25 +4.04K | min 0]
    change %: [max +0.22% | p75 +0.11% | median 0.00% | p25 0.00% | min 0.00%]

  heap_increase:
    status:   No significant changes 👍
    counts:   [total 3 | regressed 0 | improved 0 | new 0 | unchanged 3]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

  stable_memory_increase:
    status:   No significant changes 👍
    counts:   [total 3 | regressed 0 | improved 0 | new 0 | unchanged 3]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

---------------------------------------------------
CSV results saved to canbench_results.csv

github-actions · 2025-08-15T11:33:03Z

`canbench` 🏋 (dir: ./benchmarks/vec) `63579e8` 2025-08-16 09:14:15 UTC

✅ ./benchmarks/vec/canbench_results.yml is up to date
📦 canbench_results_vec.csv available in artifacts

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

Summary:
  instructions:
    status:   No significant changes 👍
    counts:   [total 16 | regressed 0 | improved 0 | new 0 | unchanged 16]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

  heap_increase:
    status:   No significant changes 👍
    counts:   [total 16 | regressed 0 | improved 0 | new 0 | unchanged 16]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

  stable_memory_increase:
    status:   No significant changes 👍
    counts:   [total 16 | regressed 0 | improved 0 | new 0 | unchanged 16]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

---------------------------------------------------
CSV results saved to canbench_results.csv

github-actions · 2025-08-15T11:33:03Z

`canbench` 🏋 (dir: ./benchmarks/io_chunks) `63579e8` 2025-08-16 09:15:08 UTC

✅ ./benchmarks/io_chunks/canbench_results.yml is up to date
📦 canbench_results_io_chunks.csv available in artifacts

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

Summary:
  instructions:
    status:   Improvements detected 🟢
    counts:   [total 18 | regressed 0 | improved 1 | new 0 | unchanged 17]
    change:   [max +47.81K | p75 +168 | median 0 | p25 0 | min -40.98M]
    change %: [max 0.01% | p75 0.00% | median 0.00% | p25 0.00% | min -2.16%]

  heap_increase:
    status:   No significant changes 👍
    counts:   [total 18 | regressed 0 | improved 0 | new 0 | unchanged 18]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

  stable_memory_increase:
    status:   No significant changes 👍
    counts:   [total 18 | regressed 0 | improved 0 | new 0 | unchanged 18]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

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

Only significant changes:
| status | name                | calls |   ins |  ins Δ% | HI |  HI Δ% |   SMI |  SMI Δ% |
|--------|---------------------|-------|-------|---------|----|--------|-------|---------|
|   -    | write_chunks_vec_1m |       | 1.86B |  -2.16% |  0 |  0.00% | 1.54K |   0.00% |

ins = instructions, HI = heap_increase, SMI = stable_memory_increase, Δ% = percent change

---------------------------------------------------
CSV results saved to canbench_results.csv

Co-authored-by: Copilot <[email protected]>

…ble-structures into maksym/free-buckets-on-clear

Co-authored-by: Copilot <[email protected]>

Copilot

Pull Request Overview

This PR introduces manual bucket release functionality to the MemoryManager to prevent memory waste during data migration scenarios. When stable structures like BTreeMap or Vec are cleared, their allocated memory buckets remain tied to the memory ID and cannot be reused by other memories, leading to memory growth.

Adds release_virtual_memory_buckets() method to manually reclaim buckets after clearing structures
Implements bucket reuse pool to allow freed buckets to be allocated to other memories
Provides comprehensive test coverage demonstrating migration scenarios and bucket reuse efficiency

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
src/memory_manager/bucket_release_tests.rs	Comprehensive test suite validating bucket release functionality and migration scenarios
src/memory_manager.rs	Core implementation of bucket release mechanism and free bucket pool management
benchmarks/io_chunks/canbench_results.yml	Performance benchmark results showing minimal instruction count changes
benchmarks/btreemap/canbench_results.yml	BTreeMap benchmark results demonstrating performance impact

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}

src/memory_manager/bucket_release_tests.rs

src/memory_manager.rs

empty

652d11b

maksymar changed the title ~~chore: empty~~ feat: release_virtual_memory_buckets Aug 15, 2025

maksymar force-pushed the maksym/free-buckets-on-clear branch 5 times, most recently from 74613ac to 641624a Compare August 15, 2025 13:32

feat: try_release_virtual_memory_buckets

acb1eb6

maksymar force-pushed the maksym/free-buckets-on-clear branch from 641624a to acb1eb6 Compare August 15, 2025 13:41

canbench --persist

279d2c2

maksymar changed the title ~~feat: release_virtual_memory_buckets~~ feat: bucket release and reuse in MemoryManager Aug 15, 2025

maksymar requested a review from Copilot August 15, 2025 14:21

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maksymar and others added 4 commits August 15, 2025 16:23

Update src/memory_manager.rs

332875d

Co-authored-by: Copilot <[email protected]>

const

a4e3f4f

const

c63236b

Merge branch 'maksym/free-buckets-on-clear' of github.com:dfinity/sta…

c75790a

…ble-structures into maksym/free-buckets-on-clear

maksymar requested a review from Copilot August 15, 2025 14:29

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maksymar and others added 5 commits August 15, 2025 16:31

.

c7c8ece

Update src/memory_manager.rs

1de8b85

Co-authored-by: Copilot <[email protected]>

Update src/memory_manager.rs

dfcc206

Co-authored-by: Copilot <[email protected]>

remove struct type empty check

de4e9ef

docs

00af4cb

maksymar requested a review from Copilot August 15, 2025 15:52

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maksymar and others added 4 commits August 15, 2025 17:55

Update src/memory_manager.rs

0998199

Co-authored-by: Copilot <[email protected]>

fmt

8aeca47

Update src/memory_manager.rs

0ac6e0a

Co-authored-by: Copilot <[email protected]>

.

eb42f65

maksymar requested a review from Copilot August 15, 2025 16:00

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maksymar added 7 commits August 15, 2025 18:13

canbench --persist

0b3993d

improve bucket release tests with 2 migration scenarios

58b5790

.

2716105

.

a59a78a

.

b659f2a

.

638d553

.

9dda812

maksymar requested a review from Copilot August 16, 2025 08:58

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maksymar changed the title ~~feat: bucket release and reuse in MemoryManager~~ feat: add manual bucket release functionality to prevent memory waste Aug 16, 2025

maksymar added 2 commits August 16, 2025 11:06

.

a0b9423

release_virtual_memory_buckets

33a0727

maksymar requested a review from Copilot August 16, 2025 10:52

Copilot AI reviewed Aug 16, 2025

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maksymar changed the title ~~feat: add manual bucket release functionality to prevent memory waste~~ feat: add manual bucket release to prevent memory waste Aug 16, 2025

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Pull Request Overview

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