From mboxrd@z Thu Jan 1 00:00:00 1970 From: Frank Rowand Subject: Re: [PATCH] rt-tests: incorrect first latency value for --verbose option Date: Mon, 7 May 2012 14:45:47 -0700 Message-ID: <4FA8428B.4050809@am.sony.com> References: <4FA1CB20.5000209@am.sony.com> Reply-To: Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Cc: "Rowand, Frank" , "linux-rt-users@vger.kernel.org" , "williams@redhat.com" To: John Kacur Return-path: Received: from tx2ehsobe003.messaging.microsoft.com ([65.55.88.13]:45788 "EHLO tx2outboundpool.messaging.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751062Ab2EGVqQ (ORCPT ); Mon, 7 May 2012 17:46:16 -0400 In-Reply-To: Sender: linux-rt-users-owner@vger.kernel.org List-ID: On 05/07/12 14:41, John Kacur wrote: > > > On Wed, 2 May 2012, Frank Rowand wrote: > >> >> When the --verbose option is selected, the first value for each thread is >> incorrectly reported as zero. >> >> This is because when collecting the first value, the index into stat->values is >> incremented from zero to one before storing the value. But when printing the >> values, the first value printed is stat->values[0], which has been initialized >> to zero. > > Hi Frank > > Ok, no more posting from me after winning a bottle of whiskey at the Irish > Pub on quiz night. :) Or if you do, you should share a bit of the whiskey with me. > > I've been looking at this one, and I'm not sure about it. > According to the help output, > > "-v --verbose output values on stdout for statistics > format: n:c:v n=tasknum c=count v=value in us" > > ./cyclictest --verbose -p99 -t | awk '$2~/^0/{ print }' > > 0: 0: 0 > 1: 0: 0 > 2: 0: 0 > 3: 0: 0 > 4: 0: 0 > 5: 0: 0 > 6: 0: 0 > 7: 0: 0 > > So, it looks like the values are 0 at count 0, doesn't that make sense? Nope. The event for count == 0 is the first event. And the first event has an actual latency that is not zero on the system I tested it on. -Frank