Date: Sun, 20 Feb 2005 06:41:10 -0800
From: "Martin J. Bligh" <mbligh@aracnet.com>
To: Joerg Sommrey <jo@sommrey.de>
Cc: Linux kernel mailing list <linux-kernel@vger.kernel.org>
Subject: Re: Question on CONFIG_IRQBALANCE / 2.6.x
Message-ID: <318120000.1108910469@[10.10.2.4]>
In-Reply-To: <20050218225722.GA11292@sommrey.de>
References: <20050218213332.GA13485@sommrey.de> <4440000.1108766389@flay> <20050218225722.GA11292@sommrey.de>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Content-Disposition: inline
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1248
Lines: 27

>> > there's something I don't understand:  With IRQBALANCE *enabled* almost
>> > all interrupts are processed on CPU0.  This changed in an unexpected way
>> > after disabling IRQBALANCE: now all interrupts are distributed uniformly
>> > to both CPUs.  Maybe it's intentional, but it's not what I expect when a
>> > config option named IRQBALANCE is *disabled*.
>> > 
>> > Can anybody comment on this?
>> 
>> If you have a Pentium 3 based system, by default they'll round robin.
>> If you turn on IRQbalance, they won't move until the traffic gets high
>> enough load to matter. That's presumably what you're seeing.
> 
> It's an Athlon box that propably has the same behaviour.  Just another
> question on this topic:  with IRQBALANCE enabled, almost all interupts
> are routet to CPU0.  Lately irq 0 runs on CPU1 and never returns to CPU0
> - is there any obvious reason for that?

If it's not getting interrupts at 1010 per second or so, it won't rotate
them, on the grounds it's not worthwhile.

M.

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/