From mboxrd@z Thu Jan 1 00:00:00 1970 From: John Kacur Subject: Re: [RFC] [rt-tests] change to cyclictest behavior Date: Wed, 6 Jan 2010 20:39:25 +0100 Message-ID: <520f0cf11001061139j2af13403qfcbf567647bdfaa8@mail.gmail.com> References: <20100106130400.7f30ae55@torg> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: RT , LKML To: Clark Williams Return-path: Received: from mail-ew0-f219.google.com ([209.85.219.219]:40332 "EHLO mail-ew0-f219.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932455Ab0AFTj1 convert rfc822-to-8bit (ORCPT ); Wed, 6 Jan 2010 14:39:27 -0500 In-Reply-To: <20100106130400.7f30ae55@torg> Sender: linux-rt-users-owner@vger.kernel.org List-ID: On Wed, Jan 6, 2010 at 8:04 PM, Clark Williams wr= ote: > RT-ers, > > I have a problem with the way cyclictest sets up measurement threads, > but before I went and changed things I thought I would ask if people > cherished this particular behavior. > > Currently, when cyclictest is run with multiple threads (i.e. -t > option) it distributes both the sample interval and the realtime > priority by adding the 'distance' parameter to the interval and > decrementing the priority by one. This means if you have a distance o= f > 500us (default), a specified RT priority of 95 and start four threads= , > they will be started with the following parameters: > > $ cyclictest -t4 -p95 > > Will give you: > > thread =A0 =A0 =A0 =A0 =A0priority =A0 =A0 =A0 =A0sample interval > 0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 95 =A0 =A0 =A0 =A0 =A0 =A0 =A0500 > 1 =A0 =A0 =A0 =A0 =A0 =A0 =A0 94 =A0 =A0 =A0 =A0 =A0 =A0 =A01000 > 2 =A0 =A0 =A0 =A0 =A0 =A0 =A0 93 =A0 =A0 =A0 =A0 =A0 =A0 =A01500 > 3 =A0 =A0 =A0 =A0 =A0 =A0 =A0 92 =A0 =A0 =A0 =A0 =A0 =A0 =A02000 > > What I'd like to do is modify this logic so that when '-a' (affinity)= is > specified, the priority and sample interval will not be altered. I > don't think there's any point in distributing the priority's and > sample intervals when the measurement threads are pinned to their own > CPU. > > So: > > $ cyclictest -t4 -p95 -a > > Would have each thread at SCHED_FIFO 95 and a sample interval of 500u= s. > > Note that this behavior also occurs when the histogram (-h) option is > specified). > > Thoughts? > Seems reasonable to me. Maybe it would also be nice to have a flag to get the old behaviour back even with -a? John -- To unsubscribe from this list: send the line "unsubscribe linux-rt-user= s" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html