Re: Average number of instructions per line of kernel code

[J. Scott Kasten]

On Thu, 30 Aug 2007, Mohamed Bamakhrama wrote:
> > > 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-
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