GSOC 2013 project " Kernel Size Reduction for Embedded System "

[Joshua Isom]

On 4/9/2013 1:47 PM, Edward Tomasz Napierała wrote:
> In order to optimize - in this case for size - we need a way to measure
> what should we focus on, and it looks like we don't have it yet.
>
> Would it be possible to write a tool - e.g. by instrumenting LLVM - that
> would make it possible to calculate, for every function in the call graph,
> the amount of code in that function and everything it "pulls in", i.e. all
> the code paths that it might call.  When we have that, clustering the graph
> should give us some idea what to focus on.
>
> Or perhaps such a tool already exists?
>

Would clang's LTO help for size?  I know work's starting on the bsd 
elftools ld, but I doubt it has any LTO support yet.  Running -Os on the 
kernel as a whole instead of object files could probably help a lot 
also.  I might try to set it up and see a size comparision.

Also, what about the userland?  Linux got popular for embedded partly 
for busybox and uclibc.  If Linux didn't exist, someone would have 
ported minix instead.