Re: Average number of instructions per line of kernel code

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On 8/30/07, Tom St Denis <tstdenis@xxxxxxxxxxxxxxxx> wrote:
> 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
> > architecture, compiler used, optimizations used, type of code, coding
> > style, etc...
> > I would like to know a rough estimate for such a quantity for the
> > kernel 2.4/2.6 code running on MIPS32 architecture compiled using GCC.
> > My estimate is between 5-10 instructions. I googled for such a thing
> > but couldn't find any useful papers/resources.
> >
>
> I don't understand what use this metric is.
>
> For starters, not all lines are created equal.  Not all lines contain
> code, not all lines with code produce output (hint: dead code).  Not all
> lines contain a single statement, etc....
>

Hi,
I understand that it doesn't sound interesting at all for programmers.
Nevertheless, this metric is interesting for hardware architects since
it gives you a hint about the instruction cache behavior of your code.
If somehow you know how many instructions can result from one
statement *on average*, then it can help you somehow in calculating
optimal parameters for the cache (assuming that you can find the
length of the basic blocks within your C code).


-- 
Mohamed

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