Re: question on incoming packets and scheduler

[Davide Libenzi <davidel@xmailserver.org>]

On Wed, 15 Oct 2003, Chris Friesen wrote:

> Davide Libenzi wrote:
> > On Tue, 14 Oct 2003, Chris Friesen wrote:
>
> >>I have a long-running cpu hog background task, and a high-priority
> >>critical task that waits on a socket for network traffic.  When a packet
> >>comes in, I'd like the cpu hog to be swapped out ASAP, rather than
> >>waiting for the end of the timeslice.  Is there any way to make this happen?
>
>
> > What do you mean for high priority? Is it an RT task? The wakeup (AKA
> > inserion in the run queue) happen soon :
> > IRQ->do_IRQ->softirq->net_rx_action->ip_rcv->...
> > but if your task is not RT there no guarantee that it'll preempt the
> > current running.
>
> Yes, it was an RT task.
>
> It appears that 2.4.20 fixes this issue, but there is another one
> remaining that the latency appears to be dependent on the number of
> incoming packets.  See thread "incoming packet latency in 2.4.[18-20]"
> for details.  This behaviour doesn't show up in 2.6, and I'm about to
> test 2.4.22.

Are you sure it's not a livelock issue during the burst?


- Davide