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Date: Fri, 23 Jun 2006 01:31:28 -0600
From: "Brian F. G. Bidulock" <bidulock@openss7.org>
To: Robert Hancock <hancockr@shaw.ca>
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       =?iso-8859-1?Q?=22P=E1draig=22Brady?= <P@draigBrady.com>,
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Subject: Re: Dropping Packets in 2.6.17
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Robert,

On Thu, 22 Jun 2006, Robert Hancock wrote:
> 
> If you want to give more priority to processing network packets at the 
> expense of user processes then you likely need to increase the priority 
> of the ksoftirqd thread(s). These compete for CPU time like any other 
> processes.
> 

I don't think that's a fair statement:

 - "any other process" does not execute when returning from an interrupt
    as do softirq threads

 - "any other process" does not execute upon local_bh_enable().

 - "any other process" is blockable (which at softirq is a big BUG()).

Under moderate to heavy load, throttling (or disabling) hard interrupts
effectively reduces the priority of ksoftirqd threads (they have less
opportunity to run because interrupts are returning less often).