PSA: Upcoming Wasm memory limit may break your canisters

[icme]

@ulan

in few weeks we will propose a replica change that will initialize the new wasm_memory_limit field of canister settings to 3GiB by default. That will effectively reduce the Wasm memory available to a canister from 4GiB to 3GiB.

I understand the motivation behind this, but reducing from 4GiB to 3GiB is somewhat drastic. What about a smaller increment, like from 4GiB or 3.8-3.9GiB? That still leaves 100-200MB of heap available if the developer hits the new wasm memory limit which should be enough for recovery or migration, right?

Also, I remember proposing the canister_on_low_heap_memory hook for canisters in Canister Lifecycle Hooks

Would a higher “safe” limit plus adding a heap memory lifecycle hook suffice?

Also, as a follow-up, what are the implications of this feature on the work that’s being done to bring 64-bit heap memory to canisters?