search_graph: strengthen provisional cache by tracking more info in the happy path

[lcnr]

See the added inline comment

r? BoxyUwU

[rustbot]

BoxyUwU is currently at their maximum review capacity.
They may take a while to respond.

[lcnr]

this fast path meant exponential blowup in ml-kem ended up causing a hang. let's instead just track all nested goals

View changes since the review

[lcnr]

@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: 4fcc7a6 (4fcc7a6db761f82fbe08fb9c1fb17ea68c0758ca, parent: 4ddb0b7f8ecda9dbdbcbc0519c9988badbd65d1c)

[rust-timer]

Finished benchmarking commit (4fcc7a6): comparison URL.

Overall result: ❌ regressions - please read:

Benchmarking means the PR may be perf-sensitive. It's automatically marked not fit for rolling up. Overriding is possible but disadvised: it risks changing compiler perf.

Next, please: If you can, justify the regressions found in this try perf run in writing along with @rustbot label: +perf-regression-triaged. If not, fix the regressions and do another perf run. Neutral or positive results will clear the label automatically.

@bors rollup=never
@rustbot label: -S-waiting-on-perf +perf-regression

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.7%	[0.2%, 1.5%]	10
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (primary 0.7%, secondary 7.9%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	4.1%	[4.1%, 4.1%]	1
Regressions ❌ (secondary)	7.9%	[1.6%, 18.1%]	9
Improvements ✅ (primary)	-2.7%	[-2.7%, -2.7%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.7%	[-2.7%, 4.1%]	2

Cycles

Results (primary 2.0%, secondary 0.6%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	2.0%	[2.0%, 2.0%]	1
Regressions ❌ (secondary)	2.1%	[2.0%, 2.2%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.4%	[-2.4%, -2.4%]	1
All ❌✅ (primary)	2.0%	[2.0%, 2.0%]	1

Binary size

This perf run didn't have relevant results for this metric.

Bootstrap: 489.39s -> 485.808s (-0.73%)
Artifact size: 393.41 MiB -> 393.44 MiB (0.01%)