valuelog: split sealed vs current mmap telemetry

[snissn]

Summary

• split value-log mmap residency stats into current-writable vs sealed mapped segments/bytes
• export sealed-map-denied counters so Celestia runs can show when the sealed lazy-map budget forces ReadAt fallback
• extend residency tests to assert the split accounting and denied-count aggregation

Why

• the new mmap policy cut file-backed RSS materially, but the next iteration needs cleaner runtime evidence
• separating current-vs-sealed residency tells us whether remaining mapped bytes are from the one hot writable segment or from sealed-segment reuse
• sealed-map-denied counts make the fallback behavior explicit instead of inferred from Pss_File

Validation

• go test ./TreeDB/internal/valuelog -run 'MmapResidencyStats|SealedLazyMmapBudget|PromoteCurrentWritable'
• go test ./TreeDB/db ./TreeDB/caching
• go vet ./TreeDB/internal/valuelog ./TreeDB/db ./TreeDB/caching

Stack

• base: valuelog: bound sealed mmap growth and export residency stats #827

[Copilot]

Pull request overview

This PR splits the value-log mmap residency telemetry into current-writable vs sealed-segment categories and exports a new sealed-map-denied counter. This builds on the mmap budgeting work in #827 to provide finer-grained runtime observability of which mapped bytes come from the hot writable segment versus sealed-segment reuse.

Changes:

• Split MmapResidencyStats return values from 4 to 6, separating current-writable and sealed segment/byte counts, while preserving backward-compatible aggregate active_* stats keys.
• Added sealedMapDeniedCount atomic counter on File and new SealedMapDeniedStats() aggregation on Manager, exported in both db and caching stats maps.
• Updated the residency test to validate the split accounting and denied-count aggregation.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
TreeDB/internal/valuelog/manager.go	Split MmapResidencyStats return values; added sealedMapDeniedCount field and SealedMapDeniedStats() method
TreeDB/internal/valuelog/reader_mmap.go	Increment sealedMapDeniedCount when sealed lazy mmap is denied
TreeDB/internal/valuelog/manager_test.go	Updated test to assert split current/sealed accounting and denied stats
TreeDB/db/api.go	Export new split and denied stats keys in DB.Stats()
TreeDB/caching/db.go	Export new split and denied stats keys in caching DB.Stats()

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[Copilot]

Pull request overview

This PR refines value-log mmap telemetry to better distinguish mapped residency sources and to make sealed-segment mmap budget behavior observable in production runs.

Changes:

• Split Manager.MmapResidencyStats() into current-writable vs sealed mapped segments/bytes, and propagate the new stats into both backend (TreeDB/db) and cached (TreeDB/caching) Stats() outputs.
• Track and export a sealed lazy-mmap “denied” counter (budget exhaustion) aggregated across files.
• Update valuelog manager tests to assert split residency accounting and denied-count aggregation.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
TreeDB/internal/valuelog/reader_mmap.go	Increment per-file denied counter when sealed lazy-mmap is disallowed.
TreeDB/internal/valuelog/manager.go	Add denied counter field, split residency stats into current vs sealed, and add an aggregate denied-stats method.
TreeDB/internal/valuelog/manager_test.go	Extend residency aggregation test for the split counters and denied aggregation.
TreeDB/db/api.go	Export new split residency stats and sealed-map-denied counter in backend DB Stats().
TreeDB/caching/db.go	Export new split residency stats and sealed-map-denied counter in cached DB Stats().

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[Copilot]

Pull request overview

This PR enhances value-log mmap telemetry by splitting residency accounting into current-writable vs sealed segments, and by exposing counters for when sealed lazy-mapping is denied (forcing ReadAt fallback).

Changes:

• Split MmapResidencyStats into current vs sealed segments/bytes and plumb new metrics into DB stats outputs.
• Track and aggregate sealedMapDeniedCount across files and export it via SealedMapDeniedStats.
• Extend unit tests to validate the split residency accounting and denied-count aggregation.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
TreeDB/internal/valuelog/reader_mmap.go	Increment per-file counter when sealed lazy-mmap is denied.
TreeDB/internal/valuelog/manager.go	Split mmap residency stats (current vs sealed) and add aggregated denied-count stats.
TreeDB/internal/valuelog/manager_test.go	Update tests to assert split residency accounting and denied-count aggregation.
TreeDB/db/api.go	Export the new split metrics and denied counter in DB stats map.
TreeDB/caching/db.go	Export the new split metrics and denied counter in caching DB stats map.

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[Copilot]

Pull request overview

Splits value-log mmap residency telemetry into current-writable vs sealed segments/bytes and exposes a counter for when sealed lazy-mmap is denied, enabling clearer runtime evidence of mmap policy behavior.

Changes:

• Split MmapResidencyStats into current vs sealed segment/byte aggregates and update Stats exporters accordingly.
• Track and export sealedMapDeniedCount so runs can observe when sealed lazy-mmap is denied.
• Extend residency tests to assert the new split accounting and denied-count aggregation.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
TreeDB/internal/valuelog/reader_mmap.go	Records per-file denied counts when sealed lazy-mmap is not allowed.
TreeDB/internal/valuelog/manager.go	Splits mmap residency stats and adds aggregation for sealed-map-denied counts.
TreeDB/internal/valuelog/manager_test.go	Updates/extends tests to validate new split stats and denied aggregation.
TreeDB/db/api.go	Exports new split residency stats and the denied counter in DB Stats.
TreeDB/caching/db.go	Mirrors DB Stats export changes for the caching DB wrapper.

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