runtime cache size

[bowenwang1996]

We cache compiled wasm modules in near-vm-runner and cache size is 1024. However, there does not seem to be a size limit of the compiled wasm module, which means that this cache can potentially be very large, if exploited by an adversary. While there is a no_cache flag, it is not turned on by default and also I assume it will compromise performance.

[MaksymZavershynskyi]

Wasm contract size is limited here: https://github.com/nearprotocol/nearcore/blob/05a82d8dd74531b21567623ab0e7e75946afea19/runtime/near-vm-logic/src/config.rs#L68

The size of the compiled contract should be proportional to the Wasm contract, at least on x86 architecture. CC @olonho to correct me if I am wrong.

[bowenwang1996]

So potentially this cache can be 4GB large? That seems a bit too much.

[MaksymZavershynskyi]

What is our target hardware?

[bowenwang1996]

I think the minimum requirement is 4GB of memory https://docs.nearprotocol.com/docs/roles/validator/hardware

[olonho]

Indeed if we'll get rather large contract, it may exhaust our resources, and it's indeed unlikely that non-optimizing compilers may produce binaries disproportionally non-linear from input+dependencies size.

[MaksymZavershynskyi]

Okay, let's cut it down to 128 size and deal with it later, if it turns out too small. In the future, we can back the cache with the disk rather than memory only.