From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthieu Bec Subject: good load / stress suite? Date: Tue, 15 May 2012 16:08:13 -0700 Message-ID: <4FB2E1DD.7020203@gmto.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit To: linux-rt-users@vger.kernel.org Return-path: Received: from rainbow.obs.carnegiescience.edu ([192.91.178.46]:52079 "EHLO rainbow.gmto.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758164Ab2EOXYf (ORCPT ); Tue, 15 May 2012 19:24:35 -0400 Received: from localhost.localdomain ([216.2.92.138]) (authenticated bits=0) by rainbow.gmto.org (8.14.4/8.14.4) with ESMTP id q4FN8DMI009334 (version=TLSv1/SSLv3 cipher=DHE-RSA-CAMELLIA256-SHA bits=256 verify=NO) for ; Tue, 15 May 2012 16:08:13 -0700 Sender: linux-rt-users-owner@vger.kernel.org List-ID: Hello all, I was wondering what people used to check RT_PREEMPT behavior under load/stress? I'm trying to test the accuracy of my timers and have a test where I setup a kernel module with an hr-timer flipping RTS bit on serial COM0 periodically, which I can look on an oscilloscope. the scope triggers on rising edge, I call jitter what shows on the falling side: under no specific load I get ~ 10 us (worst case waiting a long time) My initial idea for stressing the system was to compile a kernel, make -j 8 (#cores) that I thought would exercise CPU and IO if anything. As it happens, it's "mostly good" but I do get occasional (but repeatable) wild excursions (>100us) Looking around, I found a tool called 'stress' - http://weather.ou.edu/~apw/projects/stress/ Under these new conditions, the system behaves really well again ~20 us stable all the way. So both tests give different result, I'm not sure which to trust. I was thinking maybe there is some weird interaction with the kernel and building the kernel that make the 'bad' test invalid? I have RT_PREEMPT 3.0.18-rt34 SMP x86_64 Thanks, -- Matthieu