Re: Average number of instructions per line of kernel code

On Thu, 30 Aug 2007, Mohamed Bamakhrama wrote:

quoted

quoted

Hi all,
I have a question regarding the average number of assembly
instructions per line of kernel code. I know that this is a difficult
question since it depends on many factors such as the instruction set

Here's a quick answer, not the best, but quick.

I took a user space flash memory driver I'm doing at work and compiled it on my R5000 at home using gcc 4.1 and the MIPS3 abi, stopping with a .o file.  I also ran the source through cpp and a couple of grep passes to strip out junk that wasn't really code.  This driver may be somewhat typical of what you would run into as it has quite a few inline functions and such.

The driver.o was about 23000 bytes.  Forgetting about the symboltables and just dividing by 4 to estimate instructions and dividing by about 1650 net lines of code, I got about 3.5 instructions per line of C code.

I'm guessing that ball park, you're looking at 3-5 average - 10 seems high except in sections with lots and lots of inlines.

Regards,

-S-