[shreyas-blacksmith]

Summary

censusRecorder.OnEvict derived neverRead from lastAccess == addedAt. The boot scan seeds every existing file with addedAt == lastAccess (file mtime; atime is frozen at creation on noatime mounts) and accessState = itemStateBootScanned, so after a restart every eviction of an untouched pre-existing object counted as never-read: on prod, 13 of 13 evicting tenants showed 100% evicted-unread since the .16 roll. The per-class array already used the access state; the eviction accounting now switches on it:

switch value.accessState {
case itemStateNew:          // written this process, never hit
    acc.evictedNeverReadByes += size
case itemStateTouched:      // lastAccess is a real hit
    evictedLiveBytes / evictedByLastReadAge[...]
// itemStateBootScanned: no read history either way
}

Boot-scanned evictions still count in evicted_bytes, evicted_entries and the created-age histogram; they no longer appear as never-read (scalar + bazel_remote_disk_cache_evicted_never_read_{bytes,entries} counters) nor as recently read (evicted_live_bytes, last-read buckets), since the only timestamp they carry is file metadata. TestCensusBootScannedIsUnknownNotNeverRead asserts all of it alongside the class array.

Link to Devin session: https://app.devin.ai/sessions/df6c6655558146b9bafe936b062e49e7
Open in Devin Desktop: https://app.devin.ai/desktop/session/df6c6655558146b9bafe936b062e49e7?variant=devin
Requested by: @shreyas-blacksmith

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^{Need help on this PR? Tag @codesmith-bot with what you need. (Staging)}

[devin-ai-integration]

I'll fix CI failures and address comments from users with write access. I'll skip comments containing "(aside)".

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[blacksmith-staging]

Restart: boot-scanned evictions not never-read

After a restart, evicting the 10 untouched boot-scanned blobs no longer counts as never-read in the census row or the Prometheus counters. evicted_bytes still counts them.

_Merge-base

_{This PR 181fdc42}

Also checked · 3 match

Runtime unread evictions still never-read
No read history claimed for boot-scanned
Read entries still count as last-read

_{Proof on 181fdc42 (from 7d9ab6ea) · Did Proof get it right? Yes · No}

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