Gas Billing

Tags: “Gas” “Smart Contract” “Virtual Machine” “

EVM virtual machines have a set of Gas mechanisms to measure the CPU, memory and storage resources consumed by the chain on each transaction。FISCO BCOS introduces Precompiled contract, supports built-in C++In order to improve the security of precompiled contracts, FISCO BCOS v2.4.0 introduces the Gas mechanism in precompiled contracts。

Precompiled contracts support Gas calculations

Module Architecture

In FISCO BCOS v2.4.0, the ‘PrecompiledGas’ module is added to calculate gas. The gas overhead includes CPU, memory, and storage. The module diagram is as follows:

‘PrecompiledGas’ mainly records the basic operations called during the execution of the Precompiled contract for each transaction, and the Gas that consumes memory

  • When the virtual machine executes a transaction and calls the ‘call’ interface of the ‘Precompiled’ contract, each time a basic operation is called, the corresponding ‘OPCode’ is added to the ‘PrecompiledGas’Runtime Instruction Collection中

  • When the virtual machine executes a transaction and calls the ‘call’ interface of the ‘Precompiled’ contract, the memory consumed by the runtime of the ‘PrecompiledGas’ will be updated when the memory occupied by the basic operation changes

  • After the ‘Precompiled’ contract is executed, you can call the interface to calculate the Gas consumption of the ‘Precompiled’ contract based on the set of instructions executed and the memory consumed during the running of the ‘Precompiled’ contract。

Precompiled contract Gas measure

The FISCO BCOS Precompiled contract Gas measurement standard refers to EVM, which mainly includes CPU, memory and storage dimensions。The following details the specific Gas calculation method for precompiled contracts。

Precompiled Contract Memory Gas Calculation

Precompiled contract memory consumption mainly comes from input, output and additional memory consumption at runtime。When the total memory consumed by a transaction is’ txMemUsed ‘, the corresponding memory gas is calculated as follows。That is, add ‘memoryGasUnit’ gas every 32 bytes, and the value of ‘memoryGasUnit’ is 3

    MemoryGas(txMemUsed) = memoryGasUnit * txMemUsed / 32 + (txMemUsed * txMemUsed)/512

Precompiled Contract CPU, Storage Gas Compute

In order to calculate the Gas consumed by the underlying operation of the Precompiled contract, FISCO BCOS v2.4.0 maps the Precompiled contract to a specific opcode and defines the Gas corresponding to each underlying operation。

The opcode corresponding to the underlying operation of the precompiled contract

The ‘PrecompiledGas’ module maps Precompiled contract base operations to opcodes as follows:

Operation

Description

Opcode

EQ

EQ call to ConditionPrecompiled to determine whether two operands are equal

0x00

GE

GE call of ConditionPrecompiled to judge whether the left value is greater than or equal to the right value

0x01

GT

GT call of ConditionPrecompiled to determine whether the left value is greater than the right value

0x02

LE

The LE call of ConditionPrecompiled to determine whether the left value is less than or equal to the right value

0x03

LT

LT call of ConditionPrecompiled to determine whether the left value is less than the right value

0x04

NE

The NE call of ConditionPrecompiled to determine whether the left value is not equal to the right value

0x05

Limit

The Limit call of ConditionPrecompiled, which limits the number of pieces of data queried from the CRUD interface

0x06

GetInt

The getInt call to EntryPrecompiled converts the string to int256 / uint256 and returns

0x07

GetAddr

GetAddress call of EntryPrecompiled, converting string to Address

0x08

Set

Set call to EntryPrecompiled, setting the value of the specified Key to the specified Value

0x09

GetByte32

EntryPrecompiled getByte32, convert string to byte 32

0x0a

GetByte64

EntryPrecompiled getByte64, converting a string to byte 64

0x0b

GetString

GetString of the EntryPrecompiled parameter to obtain the value corresponding to the input Key

0x0c

CreateTable

CreateTable call for TableFactoryPrecompiled, creating a table

0x0d

OpenTable

OpenTable call for TableFactoryPrecompiled, open table

0x0e

Select

Select call of TablePrecompiled, query table

0x0f

Insert

Insert call of TablePrecompiled to insert the specified record into the table

0x10

Update

Update call of TablePrecompiled to update the specified record in the specified table

0x11

Remove

Remove call of TablePrecompiled to delete the specified record in the specified table

0x12

PaillierAdd

homomorphic plus interface

0x13

GroupSigVerify

Group Signature Verification Interface

0x14

RingSigVerify

Ring Signature Verification Interface

0x15
Precompiled contract basis operation measure

‘PrecompiledGas’ defines the Gas consumption corresponding to each underlying operation of the Precompiled contract, as follows:

Operation Gas consumption
EQ 3
GE 3
GT 3
LE 3
LT 3
NE 3
Limit 3
GetInt 3
GetAddr 3
Set 3
GetByte32 3
GetByte64 3
GetString 3
CreateTable 16000
OpenTable 200
Select 200
Insert 10000
Update 10000
Remove 2500
PaillierAdd 20000
GroupSigVerify 20000
RingSigVerify 20000

Gas measurement

The following describes the EVM virtual machine and the Precompiled contract Gas metrics, respectively:

EVM Virtual Machine Gas Measurement

Gas Description Gas consumption
CreateGas Gas consumption for contract creation 32000
sloadGas Gas consumed to read 32 bytes of data from storage 200
sstoreSetGas Gas consumption for adding 32 bytes of data to storage 20000
sstoreResetGas Gas consumption for updating 32 bytes of stored data 5000

Precompiled contract Gas measure

Gas Description Gas consumption
CreateTableGas Gas consumption for creating a table 16000
StoreGas Gas consumption for inserting data into a table or updating data in a table 10000
RemoveGas Gas consumption for deleting data in a table 2500

Configuration Item

Note

EVM Gas metrics support plug-in configuration items in the “genesis” file