On 8/30/07, Mohamed Bamakhrama <bamakhrama@xxxxxxxxx> wrote: > 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). Then what you need is to count the actual number of statements in the code and not just lines of text. There's a very big difference there.
