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Resource limits

Beginner
Concept

Overview

The Internet Computer uses WebAssembly as the platform for executing messages of smart contracts. Since WebAssembly is Turing-complete, it can express different kinds of computations including non-terminating computations. The Internet Computer protects against non-terminating computations by limiting the number of WebAssembly instructions and other resources per message execution. The limits depend on the message type as shown in the following table.

Resource constraints and limits

Message resource limitsConstraint
Message queue limit, messages per canister500
Maximum ingress message payload2MB
Maximum cross-net inter-canister message payload2MB
Maximum same-subnet inter-canister request payload (may be deprecated at some point)10MB
Maximum response size (replicated execution)2MB
Maximum response size (non-replicated execution, i.e. in query calls)3MB
Instruction resource limitsConstraint
Instruction limit, instructions per update call/heartbeat/timer40 Billion
Instruction limit, instructions per query call5 Billion
Instruction limit, instructions per canister install/upgrade200 Billion
Instruction limit, instructions per inspect_message200 Million
Instruction limit, instructions per round7 Billion
Subnet
limits
Constraint
Subnet capacity (total memory available per subnet)700GiB
Memory resource limitsConstraint
Wasm heap memory, per canister4GiB
Wasm stable memory, per canister400GiB
Wasm stable memory, data access per replicated message2GiB
Wasm stable memory, data written per replicated message2GiB
Wasm stable memory, data access per upgrade message8GiB
Wasm stable memory, data written per upgrade message8GiB
Wasm stable memory, data access per (replicated) query1GiB
Wasm stable memory, data written per (replicated) query1GiB
Wasm module limitsConstraint
Wasm total size, per canister100MiB
Wasm code section, per canister10MiB
Wasm custom sections, per subnet2GiB
Wasm custom sections, per canister1MiB
Wasm custom sections, sections per canister16
Query call resource limitsConstraint
Query calls execution threads, per replica node4
Query calls execution threads, per canister2
Update call resource limitsConstraint
Update calls execution threads, per subnet4
Update calls execution threads, per canister1

Performance limits

The block rate varies from 0.75 blocks per second to 1.5 blocks per second depending on the subnet and the number of nodes in the subnet.

Up to 1000 messages can be included in a block. Since ICP decouples message reception from message execution, the messages included in a block are not guaranteed to be executed in the same block. Messages for different canisters maybe executed in parallel on multiple threads. ICP currently has 4 execution threads and each thread can execute up to 1000 messages. Another limiting factor in execution throughput is the number of executed Wasm instructions. ICP currently targets 2B instructions per block.

Additional notes

The expiration time of an ingress message is specified by the agent making the request, and can be up to 5 minutes.

The Internet Computer Protocol may reject WebAssembly modules for reasons such that:

  • They declare more than 50_000 functions.
  • They declare more than 1_000 globals.
  • They declare a function with more than 1_000_000 Wasm instructions.
  • They declare more than 16 exported custom sections (the custom section names with prefix icp:).
  • The number of all exported functions called canister_update <name> or canister_query <name> exceeds 1_000.
  • The sum of <name> lengths in all exported functions called canister_update <name> or canister_query <name> exceeds 20_000.
  • The total size of the exported custom sections exceeds 1MiB.

More information regarding these restrictions can be found in the Internet Computer interface specification.