From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stanislav Meduna Subject: Re: Need help to measure and tune the latency in Linux RT Date: Tue, 30 Apr 2013 14:13:07 +0200 Message-ID: <517FB553.3000001@meduna.org> References: <20130430111021.GC31290@titan.lakedaemon.net> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20130430111021.GC31290@titan.lakedaemon.net> Sender: linux-rt-users-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Cc: Ashoka K , linux-embedded@vger.kernel.org, linux-newbie@vger.kernel.org, Linux ARM Kernel , linux-rt-users@vger.kernel.org >> This critical thread is at RR priority 50. Try to put it higher than the irq thread handling your HD hardware. I've even encountered hardware where I had to put the ATA thread in the SHED_OTHER domain - see [1] for the thread. >> I used a HR timer thread with RR pri 55 to wakeup the critical thread >> every 1 milli sec to do the job. Which prio is the ksoftirqd running at? The HRTIMER interrupts are routed through it so it also has to be high enough. I got burned with this myself [2] Regards Stano [1] http://www.spinics.net/lists/linux-rt-users/msg08711.html [2] http://www.spinics.net/lists/linux-rt-users/msg08745.html