fig_01_linux-deps

Linux Dependency Graph

This experiment demonstrates the complexity of the Linux kernel. To quote the paper, "to better quantify this API complexity, we analyzed dependencies between the main components of the Linux kernel. As a rough approximation, we used the subdirectories in the kernel source tree to identify (broad) components. We used cscope to extract all function calls from the sources of all kernel components, and then for each call checked to see if the function is defined in the same component or a different one; in the latter case, we recorded a dependency. We plot the dependency graph in [this figure]: the annotations on the edges show the number of dependencies between nodes. This dense graph makes it obvious that removing or replacing any single component in the Linux kernel requires understanding and fixing all the dependencies of other components, a daunting task."

In order to run this experiment you have to run run.sh. This will download Linux from github and checkout to commit c85fb28. This program will return a .dot and a .pdf output in the output folder. For cleaning we use the script clean.sh

N.B.: We can use:the following to generete a pdf from the.dor:

dot fis.dot -Tpdf -o fis.pdf

N.B.B.: We use the following two aesthetic options in the .dot file from the paper:

edge [ fontname=Helvetica, fontcolor=blue, fontsize=35 ];
node [ fontname=Helvetica, fontcolor=black, fontsize=80,shape=box];	

Dependencies:

• cscope
• git
• graphviz

Scripts description:

• create_cscope_db.sh -> creates the cscope database of used files. We exclude drivers, arch etc.
• component_symbols.sh -> for each symbol in a defined module(e.g. net) we find all the symbols using cscope. For each symbol we find the source module.