From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Friesen Subject: Re: Why is real time pinging not possible with RT kernels? Date: Tue, 13 Jun 2017 10:06:45 -0600 Message-ID: <59400D95.8000304@windriver.com> References: <20170613115818.yjjoec3kojryuxam@linutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Cc: , To: Sebastian Andrzej Siewior , Corey Minyard Return-path: Received: from mail.windriver.com ([147.11.1.11]:37379 "EHLO mail.windriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750899AbdFMQHH (ORCPT ); Tue, 13 Jun 2017 12:07:07 -0400 In-Reply-To: <20170613115818.yjjoec3kojryuxam@linutronix.de> Sender: linux-rt-users-owner@vger.kernel.org List-ID: On 06/13/2017 05:58 AM, Sebastian Andrzej Siewior wrote: > On 2017-06-12 07:57:18 [-0500], Corey Minyard wrote: >> A few notes on what you have done: >> >> * ionice doesn't affect network I/O. >> * renice does not set real-time priorities. >> * You don't do anything with memory locking. What happens >> if memory in your program gets paged out then is required? >> * Something on the other end of the ping is running, too. It >> also needs to be real-time, too, and it's not by default. > > You forgot to mention that the real-time kernel is not automatically > overclocking the software in terms of performance (but providing > determinism). Pinging localhost *should* be reasonably quick. It's basically a test of the scheduler and context switching (once all the memory is locked in place). Chris