building computeKey cache on first fcu call

[advaita-saha]

nimbus-eth1/nimbus/config.nim

Lines 531 to 535 in 0b93236

	noValidation* {.
	hidden
	desc: "Disble per-chunk validation"
	defaultValue: true
	name: "debug-no-validation".}: bool

The default mode should be with validation, will also smooth out the UX from import to syncer. As with validation the triggering of the computeKey cache won't take place with the first fcu call which takes hours and results in the fcu call being timed out

Suggestion: defaultValue: false

[arnetheduck]

Changing the default here increases the total time it takes to import + compute cache - the way forward here is probably to check that a cache is available on normal (non-import) startup or something similar to that effect, so that it is computed before turning on networking.

[advaita-saha]

Yes there is slow down, but personally as far as I ran imports for holesky and sepolia. The slowdown is not very significant. But yes the approach for checking on start does makes sense.

[arnetheduck]

The slowdown is not very significant.

you can measure it to quantify this point, but that only makes sense to do so at mainnet scale, ie around block 20m where the database no longer fits in memory.

[arnetheduck]

#2788 addresses this somewhat

The slowdown is not very significant.

a significant part of the slowdown is due to the separation of vertex and key data in the database - when the database is big, this leads to a lot of read/write amplification as each mpt node has to be read from two tables - it's worth remembering for future reference however - if we were to join the two tables, it might very well be the case that computing during import is decently fast.