linux-kernel - Re: Linux Serial Performance

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Message-ID: <20100109194655.GA28639@gallifrey>
Date:	Sat, 9 Jan 2010 19:46:55 +0000
From:	"Dr. David Alan Gilbert" <linux@...blig.org>
To:	"Paul G. Allen" <pgallen@...il.com>
Cc:	Samuel Thibault <samuel.thibault@...-lyon.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: Linux Serial Performance

* Paul G. Allen (pgallen@...il.com) wrote:
> Well, as far as I know. Same code on both systems. The embedded device
> operates at 115200, 8N1, no flow control. It uses RPC/SLIP protocol
> for commands and data. They talk to each other, but the Linux system
> just takes forever to send the data.

What does the RPC/SLIP - the app or the Kernel?

If you have no flow control is it possible that someone is dropping a byte
somewhere any recovering?

If your device is set at the right speed (check with stty -a < /dev/ttyS??? )
then what speed does :

dd if=/dev/zero of=/dev/ttyS??? bs=1 count=10000

show, for my line set at 9k6 (on ttyS0) it's showing 1.0kB/s which
seems about right.

What's the serial card - is it an onboard card or a PCI plug in,
I've seen problems on Linux a few times where the device driver
has the speed of some plugin cards out by a factor of 8.

Dave
-- 
 -----Open up your eyes, open up your mind, open up your code -------   
/ Dr. David Alan Gilbert    | Running GNU/Linux on Alpha,68K| Happy  \ 
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