[olug] 2.4 kernel/ SMP and APIC

[VincentR]

This problem is unique to the 2.4 kernel.  

For those who didn't know, a CPU can only service one interrupt (IRQ) at a time.  
APIC (Advanced Programmable Interrupt Controller) is what enables multiple 
CPUs (SMP) to handle interrupts simultaneously.  On an SMP system with APIC 
turned off, the CPU's must take turns servicing interrupts.

You would probably only encounter this problem in circumstances where you 
are receiving a huge UDP multicast stream and the sequence of the data is important.  
Even then you must be looking for it by having sequence numbers in each message 
of the packet and then monitoring them upon receipt.

Like I said, "This is mostly an FYI thing for thought..."

----- Original Message ----- 
From: "Phil Brutsche" <phil at brutsche.us>
To: <olug at olug.org>
Sent: Wednesday, December 11, 2002 10:55 AM
Subject: Re: [olug] 2.4 kernel/ SMP and APIC


> Jonathan Warren wrote:
>  > I ran a dual processor for some time and never had any problems of
>  > this sort.  does it only show with specific network hardware?  I am
>  > just curious.
> 
> Some of these problems only show up when you push 'em really hard.
> 
> Your average desktop usually doesn't count as being pushed really hard.
> 
> I too have had (and currently have :) a number of SMP systems that have 
> never needed this.
> 
> -- 
> 
> Phil Brutsche
> phil at brutsche.us
> 
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