From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4FEED882.9070307@xenomai.org> Date: Sat, 30 Jun 2012 12:44:18 +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] question: XENO_OPT_TIMING_SCHEDLAT List-Id: Discussions about the Xenomai project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: ali hagigat Cc: xenomai@xenomai.org On 06/30/2012 12:39 PM, ali hagigat wrote: > Does this kernel config variable, CONFIG_XENO_OPT_TIMING_SCHEDLAT, > indicate the scheduling latency? If i specify 1 nano second, so all > the real time tasks will be scheduled below 1 nano second? > > It seems impossible! > > If it is the time when a timer interrupt comes and preempts a real > time task till that real time task is scheduled again ( is this the > definition of the scheduling latency?). Again this definitions seems > not OK because it can not be 1 nano second!! It is too fast to do any > thing. > > This configuration variable does not seem to have any range.... CONFIG_XENO_OPT_TIMING_SCHEDLAT is the value of /proc/xenomai/latency at boot time. /proc/xenomai/latency is an estimation of the minimum scheduling latency on your system. In order to know what to put there you should do: echo 0 > /proc/xenomai/latency Run latency under load for several hour echo minimum_latency > /proc/xenomai/latency The value put there is then subtracted to timers deadline, so that timers wake up a little bit early to compensate for the time it takes to return to user-space. -- Gilles.