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Re: [announce] [patch] limiting IRQ load, irq-rewrite-2.4.11-B5

To: Ingo Molnar <mingo@xxxxxxx>
Subject: Re: [announce] [patch] limiting IRQ load, irq-rewrite-2.4.11-B5
From: jamal <hadi@xxxxxxxxxx>
Date: Wed, 3 Oct 2001 11:14:41 -0400 (EDT)
Cc: <linux-kernel@xxxxxxxxxxxxxxx>, Alexey Kuznetsov <kuznet@xxxxxxxxxxxxx>, Robert Olsson <Robert.Olsson@xxxxxxxxxxx>, Benjamin LaHaise <bcrl@xxxxxxxxxx>, <netdev@xxxxxxxxxxx>, Linus Torvalds <torvalds@xxxxxxxxxxxxx>, Alan Cox <alan@xxxxxxxxxxxxxxxxxxx>, Simon Kirby <sim@xxxxxxxxxxxxx>
In-reply-to: <Pine.LNX.4.33.0110031528370.6272-100000@xxxxxxxxxxxxxxxxxxxxx>
Sender: owner-netdev@xxxxxxxxxxx

On Wed, 3 Oct 2001, Ingo Molnar wrote:

Robert has a driver extension (part of Alexey's iputils) that cna
generate in the 140Kpps (for 100Mbps) and about 900Kpps for the e1000, but
i'll take a look at Simons stuff if it is available. Marc Boucher has
something that is an in-kernel client/server  as well.

> 10.0.3.4 is running vanilla 2.4.11-pre2 UP, a 466 MHz PII box with enough
> RAM, using eepro100. The system effectively locks up - even in the full
> knowledge of what is happening, i can hardly switch consoles, let alone do
> anything like ifconfig eth0 down to fix the lockup. Until this kind of
> load is present the only option is to power-cycle the box. SysRq does not
> work.

use the netif_rx() return code and hardware flowcontrol to fix it.

> and frankly, this has been well-known for a long time - it's just since
> Simon sent me this testcode that i realized how trivial it is. Alexey told
> me about Linux routers effectively locking up if put under 100 mbit IRQ
> load more than a year ago, when i first tried to fix softirq latencies. I
> think if you are doing networking patches then you should be aware of it
> as well.
>

I am fully aware of it. We have progessed extensively since then. Look at
NAPI.

> your refusal to accept this problem as an existing and real problem is
> really puzzling me.
>

I must have miscommunicated. I am not saying there is no problem otherwise
i wouldnt be working on this to begin with. I am just against your shotgun
approach.

cheers,
jamal


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