From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4EA13402.8010605@domain.hid> Date: Fri, 21 Oct 2011 10:57:38 +0200 From: Gilles Chanteperdrix MIME-Version: 1.0 References: In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Subject: Re: [Xenomai-help] Interruption of sata hard driver's during real-time task running List-Id: Help regarding installation and common use of Xenomai List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Donggu Kang Cc: xenomai@xenomai.org On 10/21/2011 09:23 AM, Donggu Kang wrote: > Dear all > > > I tried to test of latnecy with a etherlab on the xenomai framework. > The etherlab is ethercat master implimentation in the Linux Evironment > and It's using normal ethernet interface card. > > In my test, I have found huge latency under hard disk stress situation. > For making hard disk stress, I ran nomal linux process that is "while: > do ls -lR / > /tmp/list; done & > /dev/ null". > After than I also run xenomai task with etherlab master api. > > The latest latency is above a 500us. It is unacepptable on my system. > When I run latency test tool of xenomai, the latency is under a 5us I am a bit at a loss here. Is the latency 5us or 500us? If the 500us latency is measured using a tool running through normal ethernet interface card, it can not be considered a real-time task, even if the task doing the measurement was created using one xenomai's skins, so the latencies you measure are linux latlencies. > > I think the real-time task and communication of NIC is intercepted by > hard disk IRQ. > > Is there any idea to prevent interruption of sata hard driver's during > real-time task run. When a real-time task runs in primary mode, it can not be interrupted by any Linux interrupt. However, a real-time task using linux services (such as linux network services), it will switch to secondary mode, and a linux irq will be able to interrupt it. -- Gilles.