Re: question on incoming packets and scheduler

[Chris Friesen]

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.

Chris




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