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From: Alan <>
To: Joe Barr <>
Cc: Linux Kernel mailing List <>
Subject: Re: Serial port blues
Date: Mon, 22 Jan 2007 11:37:58 +0000	[thread overview]
Message-ID: <20070122113758.4197911c@localhost.localdomain> (raw)
In-Reply-To: <1169242654.20402.154.camel@warthawg-desktop>

Serial port latency is heavily dependant on the HZ rate for data bits
and input side stuff and you can set the low latency flag to improve upon
that. Beyond that if you are using the modem control ioctls then it
depends a lot on the hardware. USB has some implicit queuing on the bus
but generic uarts have very little on the whole.

You should be able to get much better results by using
mlockall(MCL_FUTURE) on the actual test process and setting the priority
into the real time range, in combination with turning on low latency on
the motherboard ports. 

The current -mm kernels also support arbitary baud rate (well 45 or 50
rather than 45.5), although this hasn't yet been enabled for all
platforms or pushed into the base kernel for i386 yet. It will be soon
however and then glibc can be tweaked to use it by default.


      parent reply	other threads:[~2007-01-22 11:27 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-01-19 21:37 Joe Barr
2007-01-20 17:36 ` Willy Tarreau
2007-01-21  5:54   ` Theodore Tso
2007-01-21  7:05     ` Willy Tarreau
2007-01-21 14:04       ` Johannes Stezenbach
     [not found]         ` <>
2007-01-21 14:58           ` Willy Tarreau
     [not found]             ` <>
2007-01-21 18:52               ` Theodore Tso
     [not found]                 ` <>
2007-01-21 19:30                   ` Theodore Tso
2007-01-21 18:55       ` Theodore Tso
2007-01-21  5:09 ` Stuart MacDonald
2007-01-21  7:07 ` H. Peter Anvin
2007-01-21  7:08 ` H. Peter Anvin
2007-01-21 20:44   ` H. Peter Anvin
2007-01-22 11:37 ` Alan [this message]

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