freebsd stable - May 2011 - How to understand, what userland program does in kernel?

Hello, Freebsd-stable.

  I have userland program (transmission BT client), which spent 100%
of one core of E4500 CPU when it has many peers. It is surprises me,
as channel is only 35Mbit, and my "Linux" friends can upload much more
on comparable hardware.

  But what surprises me even more, that 50% of this time it spends as
System time.

  Is here any way to understand, what transmission does in kernel for
so much time? It seems, that userland profiling doesn't help me, am I
right?

-- 
// Black Lion AKA Lev Serebryakov <lev@FreeBSD.org>

on 04/05/2011 15:49 Lev Serebryakov said the following:
> Hello, Freebsd-stable.
> 
>   I have userland program (transmission BT client), which spent 100%
> of one core of E4500 CPU when it has many peers. It is surprises me,
> as channel is only 35Mbit, and my "Linux" friends can upload much
more
> on comparable hardware.
> 
>   But what surprises me even more, that 50% of this time it spends as
> System time.
> 
>   Is here any way to understand, what transmission does in kernel for
> so much time? It seems, that userland profiling doesn't help me, am I
> right?
ktrace can easily show you what system calls are made by your program and how
much
time they take.  Maybe that would be sufficient for you.

-- 
Andriy Gapon

Quoting Lev Serebryakov <lev@FreeBSD.org> (from Wed, 4 May 2011  
16:49:01 +0400):
> Hello, Freebsd-stable.
>
>   I have userland program (transmission BT client), which spent 100%
> of one core of E4500 CPU when it has many peers. It is surprises me,
> as channel is only 35Mbit, and my "Linux" friends can upload much
more
> on comparable hardware.
>
>   But what surprises me even more, that 50% of this time it spends as
> System time.
>
>   Is here any way to understand, what transmission does in kernel for
> so much time? It seems, that userland profiling doesn't help me, am I
> right?
ktrace and dtrace are your friends. ktrace for a simple "it makes  
those syscalls/ioctls/..." type of information gathering, and dtrace  
for in-deep investigation.

Bye,
Alexander.

-- 
The difference between a good haircut and a bad one is seven days.

http://www.Leidinger.net    Alexander @ Leidinger.net: PGP ID = B0063FE7
http://www.FreeBSD.org       netchild @ FreeBSD.org  : PGP ID = 72077137

Hello, Lev.
You wrote 4 ??? 2011 ?., 16:49:01:
>   I have userland program (transmission BT client), which spent 100%
> of one core of E4500 CPU when it has many peers. It is surprises me,
> as channel is only 35Mbit, and my "Linux" friends can upload much
more
> on comparable hardware.
>   But what surprises me even more, that 50% of this time it spends as
> System time.
  When it spents, says, 75% of one core, SYSTEM is only 1-2%, not
 75%/2 =~ 37%, what is interesting...

-- 
// Black Lion AKA Lev Serebryakov <lev@FreeBSD.org>