linux-kernel - Re: [PATCH -mm v4 6/9] atmel_serial: Split the interrupt handler

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Date:	Thu, 31 Jan 2008 20:36:25 +0100
From:	"Remy Bohmer" <linux@...mer.net>
To:	"Haavard Skinnemoen" <hskinnemoen@...el.com>
Cc:	michael <trimarchi@...dalf.sssup.it>, fabio@...dalf.sssup.it,
	"Andrew Victor" <linux@...im.org.za>,
	"Chip Coldwell" <coldwell@...hat.com>,
	"Marc Pignat" <marc.pignat@...s.ch>,
	"David Brownell" <david-b@...bell.net>,
	linux-kernel@...r.kernel.org, "Alan Cox" <alan@...rguk.ukuu.org.uk>
Subject: Re: [PATCH -mm v4 6/9] atmel_serial: Split the interrupt handler

Hello Haavard,

> It seems to be very sensitive to network traffic though...could it have
> something to do with softirq scheduling? Could you try the patch below
> and see if you can trigger the error message?

Funny that you mention this.
The largest latencies I currently have on RT (and rm9200) occur when
using a telnet session or NFS filesystems, thus while using network.
The impact on hardware Interrupt latencies are limited (<85us), so the
interrupt handler should still be able to keep up the receive buffer,
but context switches between threads can stall for a longer time under
some conditions.
A long shot, but can it be that the ringbuffer overflows, and that
therefor characters are lost?

Kind Regards,

Remy
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