readprofile ; Meaning of "Length of procedure"

readprofile ; Meaning of "Length of procedure"

[Shesha]

 Hello Linux ppl,
 
 I have copuple of questions, I request you to share the information if you
know ....
--
1
--
 In the readprofile man page load=(# of clk ticks) / (length of the procedure)
 
 What does "length of procedure" means. 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.
 
--
2
--
 What value of the procedure load is considered to be a potential CPU
intensive procedure/ high load procedure.

Say for example, if the load value is 20, then is that procedure considered to
be a high load procedure. 

Thanking You
Shesha
 

Re: readprofile ; Meaning of "Length of procedure"

[Andy Pfiffer]

On Mon, 2003-04-14 at 15:17, Shesha@asu.edu 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

Re: readprofile ; Meaning of "Length of procedure"

[Shesha]

Thanks a lot Andy, one this that is bothering me is,
Say if the load of procedures by executing the command mentioned by you is as
follows in descending order....

2604	__geneic_copy_to_user 		40.6875
1705	csum_patrial_copy_generic	6.8750
370	__generic_copy_from_user	3.75
764	do_annonymous_page		3.1754
176	handle_IRQ_event		1.5714
31	remove_wait_queue		0.96

the list goes on

are these procedures condidered as load on the CPU? how much of a load ?
very high, high, moderate .....

If you can throw some light on this, it will be great.
Thanking You
Shesha 


On Mon, 14 Apr 2003, Andy Pfiffer wrote:

> On Mon, 2003-04-14 at 15:17, Shesha@asu.edu 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
> 
> 

Re: readprofile ; Meaning of "Length of procedure"

[Andy Pfiffer]

On Mon, 2003-04-14 at 16:23, Shesha@asu.edu wrote:
> Thanks a lot Andy, one this that is bothering me is,
> Say if the load of procedures by executing the command mentioned by you is as
> follows in descending order....
> 
> 2604	__geneic_copy_to_user 		40.6875
> 1705	csum_patrial_copy_generic	6.8750
> 370	__generic_copy_from_user	3.75
> 764	do_annonymous_page		3.1754
> 176	handle_IRQ_event		1.5714
> 31	remove_wait_queue		0.96
> 
> the list goes on
> 
> are these procedures condidered as load on the CPU? how much of a load ?
> very high, high, moderate .....

Based only on the data from the fragment above, your relative percentage
of time spent breaks down like this (I'm using the 1st column):

	46%	__generic_copy_to_user (2604 / 5650)
	30%	csum_partial_copy_generic (1705 / 5650)
	13%	do_anonymous_page (764 / 5650)
	 6%	__generic_copy_from_user (370 / 5650)

Whatever you were doing when you collected this profile, your system was
spending roughly 76% of the time copying data from kernel space to user
space.

I can't tell you why it was doing that; for some applications this may
be expected and normal.  I don't find the "load" column all that useful
myself -- others will certainly differ.

Regards,
Andy

readprofile: Meaning of "Length of procedure"

[Shesha]

 Hello Linux ppl,
 
 I have copuple of questions, I request you to share the information if you
know ....
--
1
--
 In the readprofile man page load=(# of clk ticks) / (length of the procedure)
 
 What does "length of procedure" means. 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.
 
--
2
--
 What value of the procedure load is considered to be a potential CPU
intensive procedure/ high load procedure.

Say for example, if the load value is 20, then is that procedure considered to
be a high load procedure. 

Thanking You
Shesha