Inlining optimisations¶

Inlining - it is optimization during the compilation process when small functions are combined into their respective callers.

It allows: - to remove the overhead of the function call - to permit the compiler to apply other optimization strategies

Using //go:noinline we can turn of inlining for the function.

//go:noinline 
func max(a, b int) int { 
    if a > b { 
        return a 
    } 
    return b 
}

Inline budget¶

It is a cost of inlining the function, that is defined by the compiler.

 -gcflags=-m=2

Allows to see the cost the compiler assigns to each function. 2

The inlining budget can be controlled to some degree with the -gcflag=-l flag. Currently the values that apply are:

-gcflags=-l=0 is the default level of inlining.
-gcflags=-l (or -gcflags=-l=1) disables inlining.
-gcflags=-l=2 and -gcflags=-l=3 are currently unused and have no effect over -gcflags=-l=0
-gcflags=-l=4 reduces the cost for inlining non-leaf functions and calls through interfaces.

Some functions may be ineligible because of their complexity. For example: recovery, break, select, go
Functions with //go:noinline

Mid stack inlining allows functions in the middle of a call stack to be inlined without requiring everything below them to be eligible.

Splitting functions into an easily inlineable function allows to reduce the cost.