From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Samuel Subject: Re: Basic questions on the kernel Date: Fri, 30 May 2003 11:16:32 -0700 Sender: linux-newbie-owner@vger.kernel.org Message-ID: <3ED7A000.80103@bcgreen.com> References: <36993D449C7FA647BF43568E0793AB3E061CD9@nevis_pune_xchg.pune.nevisnetworks.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <36993D449C7FA647BF43568E0793AB3E061CD9@nevis_pune_xchg.pune.nevisnetworks.com> List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Girish Kale , linux-newbie@vger.kernel.org Girish Kale wrote: > Hi, > > I have a few basic questions on the kernel performance: > > 1) For embedded systems, even though standard linux may not have hard > real-time performance unless real-time patch, low latency patch are > applied, I would like to know if linux can give "deterministic" > performance. Meaning can we be guaranteed that a particular process will > be scheduled after a particular time. What are the these times or where > do I find this data. You can only get "deterministic" performance if you're using a real-time patch. I'm not sure what the timing is, but I believe that it's in the sub-milisecond range. You might be able to get near-realtime (but no absolute guarantees) by setting the process that needs fast response to nice -20 this gives it highest priority, so that it gets CPU pretty much whenever it wants it (after device drivers). > > 2) When we are using linux on an embedded system, will there a memory > management unit for this, since there will not be any swapping in/out of > pages? Can we avoid a process from keeping on allocating memory thereby > starving other applications? Linux generally wants an MMU. Embeded kernels MAY be able to survive without one (dunno). Check the setrlimit call, or the ulimit bash built=in for info on how to set resource usage limits. You can also set limits on a system-wide basis by using the /proc mechanisms. (your system probably has a formalized way of doing that automatically on boot.. for RedHat, that would be the file /etc/sysctl.conf ) -- Stephen Samuel +1(604)876-0426 samuel@bcgreen.com http://www.bcgreen.com/~samuel/ Powerful committed communication, reaching through fear, uncertainty and doubt to touch the jewel within each person and bring it to life. - To unsubscribe from this list: send the line "unsubscribe linux-newbie" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.linux-learn.org/faqs