How to understand, what userland program does in kernel?

[Alexander Leidinger]

Quoting Lev Serebryakov <lev at 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.

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