perf(evmonlyapp): hash a block's transactions before taking the sender lock

[bdchatham]

One of four independent PRs from the serial-budget survey (#4234, #4235, #4236, #4237); each targets giga-1 on its own.

takeSenders keccaked every raw transaction inside the checkedSenders lock, on the execute loop. The hashing is the whole cost of the pass, and CheckTx writes that same map about 64,500 times a second — so admission stalled for the length of a block's worth of hashes.

The hashes are now taken across the pool first, and the lock covers only the map lookups.

Measured

Measured locally with a throwaway BenchmarkHashRawTxs (not included in this PR). 1,848 transactions, 10-core machine:

	time
keccak on the loop (what it did)	791 µs — 428 ns/tx
across the pool (what it does)	231 µs

560 µs off a 28.83 ms loop, ~1.9%. A validator at GOMAXPROCS 32 has more of the pool to spread it over, so this is the floor. It costs one 59 KB slice of hashes per block.

Two things the survey did not have: the keccak is 428 ns/tx, slightly above its 300–420 ns estimate; and the lock was held across the whole pass, which it did not mention and which is the part that touches admission latency rather than throughput.

Correctness

• Lookups still run in index order, so a block carrying the same transaction twice resolves the first and leaves the second unknown — unchanged.
• TestHashRawTxsMatchesKeccak256Hash pins hashRawTxs to crypto.Keccak256Hash over 0, 1, 2, 17 and 1,848 inputs. This matters more than it looks: the map is keyed by tx.Hash(), so a hash that differs by one byte would silently lose every sender and make the executor recover all 1,848 signatures instead.
• One hasher is reset per worker rather than allocated per transaction.
• Ranges are contiguous, not strided, so workers do not share cache lines while writing.
• -race clean on the package.

Link to Devin session: https://app.devin.ai/sessions/0952787e9df84a7994fda23fea5db400
Open in Devin Desktop: https://app.devin.ai/desktop/session/0952787e9df84a7994fda23fea5db400?variant=devin
Requested by: @bdchatham

[cursor]

PR Summary

Low Risk
Behavior change is limited to when work runs and how hashes are computed; correctness hinges on Keccak parity with the prior per-tx hashing, which the new test exercises across small and large batch sizes.

Overview
Moves Keccak hashing out of the checkedSenders mutex so FinalizeBlock no longer holds that lock while hashing every raw transaction—a path that contended with high-frequency CheckTx writes to the same map.

takeSenders now calls hashRawTxs first, then locks only for map lookup/delete. hashRawTxs parallelizes hashing across GOMAXPROCS when there are more than 64 txs per worker, using a shared hashRawTxRange helper that resets one Keccak hasher per goroutine instead of allocating per tx.

Adds TestHashRawTxsMatchesKeccak256Hash so batch hashes stay identical to crypto.Keccak256Hash, which is required for sender-cache keys to match CheckTx.

^{Reviewed by Cursor Bugbot for commit 23e892a. Bugbot is set up for automated code reviews on this repo. Configure here.}

[github-actions]

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Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	Sep 17, 2026, 1:30 PM

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.70%. Comparing base (7e3ca24) to head (23e892a).
⚠️ Report is 26 commits behind head on giga-1.

Additional details and impacted files

@@             Coverage Diff             @@
##           giga-1    #4235       +/-   ##
===========================================
+ Coverage   65.55%   78.70%   +13.14%     
===========================================
  Files        2081        7     -2074     
  Lines      157460      756   -156704     
===========================================
- Hits       103222      595   -102627     
+ Misses      54097      161    -53936     
+ Partials      141        0      -141     

Flag	Coverage Δ
sei-chain	?
sei-chain-pr	83.62% <100.00%> (?)
sei-db	74.50% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
sei-tendermint/internal/evmonlyapp/app.go	82.63% <100.00%> (+0.86%)	⬆️

... and 2074 files with indirect coverage changes

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[seidroid]

Moving the keccak pass out of the checkedSenders lock and across the pool is correct and behaviour-preserving: hashes stay index-aligned, lookups still run in order so the duplicate-transaction case is unchanged, workers write disjoint contiguous ranges of hashes, and TestHashRawTxsMatchesKeccak256Hash pins the Reset/Write/Read hasher reuse to crypto.Keccak256Hash (the equality that would otherwise silently drop every sender). Two non-blocking notes: the chunking degenerates to one goroutine per transaction on blocks smaller than GOMAXPROCS, and the new godoc paragraphs carry rationale that AGENTS.md asks be kept inline.

Findings: 0 blocking | 2 non-blocking | 2 posted inline

Blockers

• None at the file/PR level.

Non-blocking

• None at the file/PR level.
• 2 suggestion(s)/nit(s) flagged inline on specific lines.