LSL Script Memory
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Script Memory
All scripts in LSL pre-MONO start out with 16 kilobytes of memory. Mono scripts start with 64 kilobytes, this may be reduced with llSetMemoryLimit(). Additionally, Mono scripts only use the amount of real memory that they currently need, not the amount allocated to them (64kB, or whatever was set by llSetMemoryLimit(). Mono scripts also share the memory needed for their bytecode with all other instances in the same region of the same script copied after compilation. Below is a list of code and the memory usage.
Much of the following data was collected through llGetFreeMemory(). The revised figures for Mono lists were obtained via llGetUsedMemory(). As the LSL compiler is not a simple program, the data below may not be 100% accurate, in fact, much of it is wrong and could use corrections.
There are still many bits that could be improved upon, and many more that could use more detail. If anyone has any free time, play around with the memory usage for different functions. A list of needed updates is at the end of the page.
Variables
See the end of this page.
Declaring variables as global
Variable Memory Usage (Pre Mono)
integer 10 float 10 string 18 + 1 per character key 18 + 1 per character vector 18 rotation 22 list 21 + list memory usage
List Memory Usage (MONO) (Revised findings as of Jan 2013)
integer 16 float 16 string 18 + 2 per character interned string 4 (must be inserted as a reference to a pre-existing string) key 102 key as string 90 vector 24 rotation 28 list Lists Can Not Contain Lists
For other results relating to Mono see https://wiki.secondlife.com/wiki/User:Omei_Qunhua
List Memory Usage (Pre MONO)
integer 15 float 15 string 12 + 1 per character key 12 + 1 per character vector 23 rotation 27 list Lists Can Not Contain Lists
String entries have a constant 8 for pre-compile text.
myList = ["testing", "1", "asdhdgkjajlgsdfdsw"]
(8, 8, 8)
myList = [llGetSubString("testing", 0, -1), (string)1, llToUpper("asdhdgkjajlgsdfdsw")]
(22 + 14, 22 + 2, 22 + 36)
Declaring variables inside default state
Variable Memory Usage
integer 15 float 15 string 12 + 1 per character key 12 + 1 per character vector 31 rotation 39 list 15 + list memory usage
List Memory Usage
integer 7 float 7 string 4 + 1 per character key 4 + 1 per character vector 23 rotation 30 list Lists Can Not Contain Lists
Simply stating values
Putting a Value onto the Stack
Integers 1 + 4 bytes for the value Float 1 + 4 bytes for the value String 1 + bytes for characters + 1 byte for null Key 1 + bytes for characters + 1 byte for null Vector 1 + 3 * float cost Rotation 1 + 4 * float cost List 1 + 4 for list length + list memory usage
To remove a value from the stack costs 1 byte.
List Memory Usage
Integers 7 Float 7 String 4 + 1 per character Key 4 + 1 per character Vector 23 Rotation 30 list Lists Can Not Contain Lists
Constants
All integer constants use 6 bytes of memory.
Other Constants
ZERO_VECTOR 16 ZERO_ROTATION 21 NULL_KEY 39
Extras
6 bytes to reference variables
Examples
integer i; //10 bytes
default {
state_entry() {
list l = ["Testing", "This"] //15 (list) + 15 (string) + 8 (string)
}
}
Functions
Declaring functions
Functions require 16 bytes to be created, with 3 bytes per parameter, plus bytes commensurate with the return type.
Tests in January 2013 show that user functions in Mono no longer (if ever) automatically take up a block of memory (512 bytes) each. As with all Mono code, an extra 512-block of memory is used when needed, but not automatically per user function. In addition the perceived memory usage can vary depending, it is thought, on the action of periodic garbage collection. Inserting an llSleep() for instance, maybe allowing garbage collection to jump in, before reading memory usage, can show a reduction in space used.
Return Types
integer 4 float 4 string 4 key 4 vector 20 rotation 27 list 4
Declaring variables in functions
Variable Memory Usage
integer 11 float 11 string 8 + 1 per character key 8 + 1 per character vector 19 rotation 23 list 11 + list memory usage
List Memory Usage
integer 7 float 7 string 4 + 1 per character key 4 + 1 per character vector 23 rotation 30 list Lists Can Not Contain Lists
Calling functions
21 bytes to call a function with no return
21 bytes to call a function with any return + type of return
Subtract number of parameters entered
Return Types
integer 2 float 2 string 10 + 1 per character returned key 10 + 1 per character returned vector 2 rotation 2 list 18 + list memory usage
Examples
list f() { //16 (function) + 4 (return)
list ret = [0]; //11 (list) + 7 (integer)
return ret; 6 (list)
}
string f() {
return "";
}
default {
state_entry() {
f(); //21 (call to f) + 10 (returns string)
}
}
Operators
List of Operators
+ 1 - 1 * 1 / 1 % 1 & 0 | 0 ^ 0 ! 0 >> 0 << 0 ~ 1 == 1 <= 1 < 1 >= 1 > 1 != 1
Assignment
Assigning values to variables takes as many bytes as used minus one.
Examples
string s; //12 bytes
s; //6 bytes
""; //3 bytes (see below)
s = ""; //8 (6 (string) + 3 (null string) - 1) bytes
However...
string s = ""; //12 bytes
integer i; //15 bytes
i = i + 1 // 6 bytes (integer) + 6 bytes (integer) + 6 bytes (1) + 1 byte (addition) - 1 byte (assignment)
Statements
if 6 while 11 for 11 do 6 jump 5 @ 0 state 5
Examples
if (5 < 10) { // 6 (if) + 6 (integer) + 6 (integer) + 1 (compare)
//Do something here
}
while (1 < 2 & 3 < 4) { // 11 (while) + 4*6 (4 integers) + 2 (2 compares)
//Do something here
}
Typecasting
integer 10 float 10 string 10 key 10 vector 10 rotation 10 list 25
States
14 bytes for any event in a state + 1 for each parameter 17 bytes to create a new state
Needed Updates
Several updates are needed for this page, the most needed are listed below:
- Verification of all data
- Clarification of explanations
- Investigations into how the functions work
- Calling of functions
- How return types effect the return
- In the following code, the call to llGetFreeMemory() returns a different value. How is it affected? Why?
default {
state_entry() {
llOwnerSay((string)llGetFreeMemory());
list l = ["", "", "", ""];
llOwnerSay((string)llGetFreeMemory());
}
}