From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 11D93C433E0 for ; Thu, 11 Mar 2021 12:59:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BF6DC64FC3 for ; Thu, 11 Mar 2021 12:59:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233294AbhCKM6u (ORCPT ); Thu, 11 Mar 2021 07:58:50 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39872 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233061AbhCKM60 (ORCPT ); Thu, 11 Mar 2021 07:58:26 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2C29BC061574 for ; Thu, 11 Mar 2021 04:58:26 -0800 (PST) Date: Thu, 11 Mar 2021 13:58:21 +0100 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1615467504; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=ZblhYSqwelKK27T7VIBot2Eooam0rHaxXRjr5Z9jJsw=; b=cNVpemUqk6FhWQvIBuC8ivFucrNzmDR9I2IIL3Lsp1LL2jVJt3rxobPyUQm/N34x8p27t5 KCSxiSD73kPrXRMg8YQQdcK9IvtWkKDjCqWLSlWNgf+8DPzzZNORIiBnwvj3hjIMKbdP86 7rAWeiBsXPeQ+URiPqg4u/VBRQ/D7g2PjMUjTVrxthdl31wIIg6OmZgZtLFAkJuAW9ryrg EcfwYhBOPCNYqqrYR0ijoTEKDdayRJ2QOattLs5aTslRulJNdFknrPWDICCJUrlsZlvPTe k1BD6RQrbnT/y4K8FahDTfMd5obYoWDfi8pPyQd1MxiD06SWe85fFHDF8MA2bw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1615467504; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=ZblhYSqwelKK27T7VIBot2Eooam0rHaxXRjr5Z9jJsw=; b=ep8MIDS4oAbaSCdFAiCFhpSgqctp75VE59+vyfdRNWghLxW8TuiifxFZMHEeTXp6Z/vTXy PwNRnY1M5RhCYNDg== From: "Ahmed S. Darwish" To: Michel Macena Oliveira Cc: linux-rt-users@vger.kernel.org Subject: Re: PREEMPT_RT benchmark Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-rt-users@vger.kernel.org On Wed, Mar 10, 2021 at 05:07:47PM -0300, Michel Macena Oliveira wrote: > > I'm currently developing a time benchmark application where I want > to measure a real time thread latency. My application is based on > Cyclictest from > the rt-tests suit. ... > > I programmed in such way that it would be equivalent to Cyclict test > ... > > At least that's what I expected, but my latencies are much bigger than > Cyclictest ones. > I don't know the nature of the "time benchmark" application you are writing. Just a small hint that if you're doing any heavy OpenGL graphics within that application, the latency can shoot up significantly. On some of our Intel boxes, this can lead to an increase of 100-200 microseconds. That's because since Intel Gen9+ GPUs, Intel shares the Last-Level Cache (and thus also memory bandwidth) between the GPU and the CPU. This benefits graphical applications, but hurts predicatbility significantly. Good luck, -- Ahmed S. Darwish Linutronix GmbH