[PLUG] What is softirq?

[Vincent Yau]

Thanks for your tip.  The noapic option indeed fixes my problem.


>From: "Jason R. Martin" <nsxfreddy at gmail.com>
>Reply-To: "Jason R. Martin" <nsxfreddy at gmail.com>, "General 
>Linux/UNIXdiscussion and help; civil and on-topic" 
><plug at lists.pdxlinux.org>
>To: "General Linux/UNIX discussion and help,civil and on-topic" 
><plug at lists.pdxlinux.org>
>Subject: Re: [PLUG] What is softirq?
>Date: Wed, 21 Sep 2005 12:07:50 -0700
>
>On 9/21/05, Vincent Yau <v_yau3 at hotmail.com> wrote:
> > Hi:
> >
> > Recently, I brought up to athlon64 box.  They both run great (most of 
>the
> > time).
> > The slower of the two, however, seems to be exhibiting some weird
> > behavior at times.  They are all sorts of them here and there
> > and I am slowly tackling one at a time.
> >
> > This one, however, is a little odd for me.
> > When I run top,   I can always see that under "CPU states", the 
>"softirq"
> > category always
> > hovers around 50% usage.  Even when I am not running anything (other 
>than
> > what is minimum to have the box running), it would be 50% idle and 50%
> > softirq.
> > I don't see this on any other boxes so I am wondering what is special 
>about
> > this.
> > Can someone tell me what is softirq?
> >
> > I am running kernel 2.4.21-32.EL  64-bit version
> >
> > Thanks for any tip/pointer.
>
>softirqs are software interrupts, used often by device drivers to do
>further processing of something outside of the hardware interrupt
>handler, which needs to run as fast as possible so interrupts can be
>re-enabled.  Perhaps you have some rogue hardware?  Does
>/proc/interrupts show something going crazy?  Is the box receiving a
>lot of network traffic?  Anything in your logs?
>
>I found this guy's posting, perhaps you should try the "noapic" option
>to see if that fixes it, then file a bug with RedHat.
>
>http://kerneltrap.org/node/5534
>
>Jason
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