Re: readprofile ; Meaning of "Length of procedure"

[Andy Pfiffer]

On Mon, 2003-04-14 at 15:17, [e-mail] wrote:
>  Hello Linux ppl,
>  
>  I have copuple of questions, I request you to share the information if you
> know ....

I have a partial answer.

> --
> 1
> --
>  In the readprofile man page load=(# of clk ticks) / (length of the procedure)
>  
>  What does "length of procedure" means.

My understanding after a quick read of the source is that "length of the
procedure" means the length, in bytes, of the function.  For most
architectures, there is not a correlation between lines of code in
assembler and number of executable bytes.

On ARM all instructions are 4 bytes long (not counting "Thumb" style
instruction encoding), but that does not mean 1 line of assembler source
code is equal to 4 bytes worth of instructions.

As far as I can tell, the "length of the procedure" is determined by the
difference between sucessive symbols found in System.map:

        .
        .
        .
        c0109414 T sys_fork
        c010943c T sys_clone
        c0109474 T sys_vfork
        c01094a0 T sys_execve
        .
        .
        .

sys_clone(), on my system, is 56 bytes long, including any alignment
padding (0xc0109474-0xc010943c = 56).

> Does that mean the # of ASM lines of
>  the procedure code? What is the units of the load. It cannot be %. because 
> -----------------------------------------------------------
>  152495 default_idle                             3176.9792 
> -----------------------------------------------------------
>  the above line indicates,  more than 100% of times CPU is idle. This cannot
> happen.

It is not a percentage.  The value is computed by:

	"load" = ticks_attributed_to_the_proc / length_of_proc

>From your example above:

	3176.9792 = 152495 / length_of_proc

therefore length_of_proc = 48 bytes.  48 looks reasonable when cross
checked with my x86 system (default_idle() is 52 bytes long on my
system).

>  What value of the procedure load is considered to be a potential CPU
> intensive procedure/ high load procedure.

There is no magic number.  However, from the readprofile man page, some
likely "high load" candidates could be found by:

	readprofile | sort -nr +2 | head -20

Regards,
Andy