From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Hunt, David" Subject: Re: [0/9] examples/vm_power: 100% Busy Polling Date: Fri, 13 Jul 2018 09:31:38 +0100 Message-ID: References: <20180621132414.39047-2-david.hunt@intel.com> <20180626092317.11031-1-david.hunt@intel.com> <2730584.abn78hPeQH@xps> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Cc: dev@dpdk.org, jerin.jacob@caviumnetworks.com, hemant.agrawal@nxp.com, arybchenko@solarflare.com, ferruh.yigit@intel.com, bruce.richardson@intel.com To: Thomas Monjalon Return-path: Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by dpdk.org (Postfix) with ESMTP id 97B0D1B476 for ; Fri, 13 Jul 2018 10:29:49 +0200 (CEST) In-Reply-To: <2730584.abn78hPeQH@xps> 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" Hi Thomas, On 12/7/2018 8:09 PM, Thomas Monjalon wrote: > 26/06/2018 11:23, David Hunt: >> This patch set adds the capability to do out-of-band power >> monitoring on a system. It uses a thread to monitor the branch >> counters in the targeted cores, and calculates the branch ratio >> if the running code. >> >> If the branch ratop is low (0.01), then >> the code is most likely running in a tight poll loop and doing >> nothing, i.e. receiving no packets. In this case we scale down >> the frequency of that core. >> >> If the branch ratio is higher (>0.01), then it is likely that >> the code is receiving and processing packets. In this case, we >> scale up the frequency of that core. >> >> The cpu counters are read via /dev/cpu/x/msr, so requires the >> msr kernel module to be loaded. Because this method is used, >> the patch set is implemented with one file for x86 systems, and >> another for non-x86 systems, with conditional compilation in >> the Makefile. The non-x86 functions are stubs, and do not >> currently implement any functionality. >> >> The vm_power_manager app has been modified to take a new parameter >> --core-list or -l >> which takes a list of cores in a comma-separated list format, >> e.g. 1,3,5-7,9, which resolvest to a core list of 1,3,5,6,7,9 >> These cores will then be enabled for oob monitoring. When the >> OOB monitoring thread starts, it reads the branch hits/miss >> counters of each monitored core, and scales up/down accordingly. > It looks to be a feature which could be integrated in DPDK libs. > Why choosing to implement it fully in an example? I needed to set up a thread that looped tightly (~100uS interval) and run it on it's own core. From what I have seen in other cases, it is usually the application that allocates cores and decides what to run on them. I did think about putting some of it in a library, but for this case I thought it made more sense to keep it purely as a sample app. Regards, Dave.