From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Bristot de Oliveira Subject: Re: [PATCH] testpmd: add nanosleep in main loop Date: Fri, 10 Nov 2017 11:42:56 +0100 Message-ID: References: <20171110060210.GA23340@amt.cnet> <20171110091219.GE24849@6wind.com> <2601191342CEEE43887BDE71AB9772585FABBC64@irsmsx105.ger.corp.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: "dev@dpdk.org" , Luiz Capitulino To: "Ananyev, Konstantin" , Adrien Mazarguil , Marcelo Tosatti Return-path: Received: from mail-wm0-f68.google.com (mail-wm0-f68.google.com [74.125.82.68]) by dpdk.org (Postfix) with ESMTP id 9E3591B6C1 for ; Fri, 10 Nov 2017 11:42:58 +0100 (CET) Received: by mail-wm0-f68.google.com with SMTP id b14so1808474wme.2 for ; Fri, 10 Nov 2017 02:42:58 -0800 (PST) In-Reply-To: <2601191342CEEE43887BDE71AB9772585FABBC64@irsmsx105.ger.corp.intel.com> Content-Language: en-US List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On 11/10/2017 11:14 AM, Ananyev, Konstantin wrote: > Agree with Adrian here - the patch doesn't fix the problem in any case, I would agree with you if it were possible to assume one can fully isolate a CPU on Linux... but it is not... This: https://lwn.net/Articles/659490/ is still an open issue, and the reason why it is an open issue is the kernel threads that need to run on every CPU, mainly when using the PREEMPT_RT, which turns almost everything on threads. > while introducing an unnecessary slowdown in testpmd iofwd mode. > Please think up some other approach. The other approach is to increase the priority of all other threads that run on the isolate CPU. But that is not a good idea at all, as the other threads might preempt the busy-loop thread at the worst possible moment. Using the knowledge of the thread about when it is the best time to give a chance for other threads to run would be a smarter decision. -- Daniel