CPU usage accounting

Mulyadi Santosa mulyadi.santosa at gmail.com
Wed Sep 14 14:44:52 EDT 2011

Hi .. :)

On Wed, Sep 14, 2011 at 21:04, Vimal <j.vimal at gmail.com> wrote:
> Hi,
> In the following cases, how does the CPU work done by the kernel on
> behalf of the application get accounted for?
> 1. When an application writes to a TCP/UDP socket, the networking
> stack does transmit side processing.
> 2. When an application receives data on a TCP/UDP socket, the
> networking stack does receive side processing.
> >From what I understand: In case (1), the kernel code executes in the
> context of the application, so the CPU cycles are accounted directly
> to process that called write() (or send/sendto).

excellent thinking, however AFAIK sometimes (or most of the times
now?) data sending is done in asynchronous style..... so the counting
might be not so accurate since we don't really know how much the data
that are transmitted...

>But in case (2),
> unless some processing is done, it is impossible to know which
> application is going to receive this packet.  Whom do these cycles get
> charged to?

excellent thinking.....  I place my bet on ksoftirqd


Mulyadi Santosa
Freelance Linux trainer and consultant

blog: the-hydra.blogspot.com
training: mulyaditraining.blogspot.com

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