RFC: Sort input section by list

[Christophe LYON]

>> What is the real purpose of this feature ?  Ie do you know why it has 
>> been requested ?  The implication of the example you have given is 
>> that the user wants to put certain name-mangled functions at the start 
>> of the .text section, but why ?
> 
> because it allows the developer to put the commonly used functions at 
> the start of the file,
> improving density in the page cache for example, and generally improving 
> startup time.
> (less pagefaults and less TLB pressure)
> 

Why not have a tool dedicated to this kind of optimization?
For one of our targets, we have developed a post linker tool which 
reorders functions based on call graph analysis.

The compiler driver asks the linker to keep all the relocations in the 
generated executable, and then calls the optimizer, which parses the ELF 
file and optionally a "layout file" to reorder code. By default it is 
used to improve locality (we have a direct mapped cache) based on static 
analysis, but can take advantage of profiling, or the user can even 
force the function order.

If the purpose is really to reorder functions, why should the developer 
need to deal with sections? (I mean, not all developers master the 
concept of section, do they?)


Christophe.