From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mails.dpdk.org (mails.dpdk.org [217.70.189.124]) by inbox.dpdk.org (Postfix) with ESMTP id 732D3A0A02; Sat, 27 Mar 2021 17:05:03 +0100 (CET) Received: from [217.70.189.124] (localhost [127.0.0.1]) by mails.dpdk.org (Postfix) with ESMTP id E941C40692; Sat, 27 Mar 2021 17:05:02 +0100 (CET) Received: from mail-pg1-f174.google.com (mail-pg1-f174.google.com [209.85.215.174]) by mails.dpdk.org (Postfix) with ESMTP id CF81C40686 for ; Sat, 27 Mar 2021 17:05:01 +0100 (CET) Received: by mail-pg1-f174.google.com with SMTP id h25so6634433pgm.3 for ; Sat, 27 Mar 2021 09:05:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=networkplumber-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=WeYGrFfob3V1EZWXlciYvwaDi7MbYSJT53Sua/fFzag=; b=vXts/pgWu2s1N3ELIEQb5c3WlqDN8qwM8wtIXjTLn/BAuYrxswpembpJfeS58bLMxh Azrfpr1dFAx327MQVOrkZVN6MiQsnDBtE830Z+3KXZsNpiLB78luYgaz/7L28H8mIuBQ CgPyN3SV07uGzDLjf790ehTV9cRsZN6ZyYGkBuxMqId0+nI2d5D+V+MlF1JhoZGelqHH ePEWZFPeQxos7quZBvqk33Yotj1tcp1+61IZ9jlT8OzlhTqixdRDuv05fPzdk7hlhFVg vBNsUUFxwGWbgqpgnFM/QFXApzti0OXxOLl6x7pnQiuWJ2pv4eEDeDab/sv+kkJIn745 NGhA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=WeYGrFfob3V1EZWXlciYvwaDi7MbYSJT53Sua/fFzag=; b=g23Ib9wvnx0MdfseoVbpKkaV1Ndsvrnt0N/1BzjsdVJVMA7bLOnedVeEjLFF2rIWE2 LQ94N+WKLLCAsFc5pSi3lLP+VPaUc6q4TNt13a761etCy8D+EC6sgwEvvduEdsIt9WBV bRHmeDHPCnlLhX61pimbXEA1wfPUHIwfkjSzV5ihvkDwVj7bXXTrlOvHLtEIezYDH5t1 jSiThZAdBsqCBOBAq7SBfYGY77y1VdBz1qCwhqw7Zf7OfTJMdWxUpiWE3KD/rmxKn88o ZuQ5SGCVPLB9t17jcwl08K9TVrdHv6obuZVngiSR2xx0vheLmNGQ/xne09mhP5YTqI5/ z/bQ== X-Gm-Message-State: AOAM532xfo3j4lY5tFERpa5EVIj4yQTG9iGqIQVb5q3yt5cIDuAe59ca WUGKN2bjPRv3kMX8NFgXRHxqWg== X-Google-Smtp-Source: ABdhPJxzYIdty8qbRN/Q4EGaEyXA+SE8h4gDVgUDM2Kt4AblgmoqmJ5x68NGLGX+ZHr8A8SYFnnQbw== X-Received: by 2002:aa7:8a56:0:b029:1f3:9c35:3cbb with SMTP id n22-20020aa78a560000b02901f39c353cbbmr17339117pfa.24.1616861100708; Sat, 27 Mar 2021 09:05:00 -0700 (PDT) Received: from hermes.local (76-14-218-44.or.wavecable.com. [76.14.218.44]) by smtp.gmail.com with ESMTPSA id q22sm11969820pfk.2.2021.03.27.09.04.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 27 Mar 2021 09:05:00 -0700 (PDT) Date: Sat, 27 Mar 2021 09:04:52 -0700 From: Stephen Hemminger To: Narcisa Ana Maria Vasile Cc: dev@dpdk.org, thomas@monjalon.net, dmitry.kozliuk@gmail.com, khot@microsoft.com, navasile@microsoft.com, dmitrym@microsoft.com, roretzla@microsoft.com, talshn@nvidia.com, ocardona@microsoft.com, bruce.richardson@intel.com, david.marchand@redhat.com, pallavi.kadam@intel.com Message-ID: <20210327090452.19750dec@hermes.local> In-Reply-To: <1616802771-31578-10-git-send-email-navasile@linux.microsoft.com> References: <1616644026-25432-11-git-send-email-navasile@linux.microsoft.com> <1616802771-31578-1-git-send-email-navasile@linux.microsoft.com> <1616802771-31578-10-git-send-email-navasile@linux.microsoft.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [dpdk-dev] [PATCH v4 09/10] eal: add EAL argument for setting thread priority X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list 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 Fri, 26 Mar 2021 16:52:50 -0700 Narcisa Ana Maria Vasile wrote: > From: Narcisa Vasile > > Allow the user to choose the thread priority through an EAL > command line argument. > > The user can select the thread priority to be either 'normal' > or 'critical': > --thread-prio normal > --thread-prio realtime > > Signed-off-by: Narcisa Vasile Please don't add this. This will open up a huge set of bugs. See the mailing list about how users report starvation and bug checks on Windows when using real time. In my experience, DPDK has same problem on Linux. The DPDK applications (usually) poll at 100% CPU without system calls. If the user sets these threads to real-time, then those threads have priority over kernel background tasks (like handling soft interrupt or writing to the disk). Therefore setting RT causes data loss or eventually RCU and watchdog timeouts. This patch encourages the fallacy that Real Time is faster. The DPDK poll usage model is not compatible with the OS defintion of real time. Real time is for processes doing system calls that have precise timing requirements about when to wakeup from those system calls.