From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Tan, Jianfeng" Subject: Re: [PATCH v6 2/2] eal: add asynchronous request API to DPDK IPC Date: Wed, 28 Mar 2018 16:55:07 +0800 Message-ID: <944ebaf4-6dc3-5069-1d7e-2ee7bbcd8adc@intel.com> References: <3396888.LEadjR7LpM@xps> <2563064.olffpIeeN1@xps> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: "Burakov, Anatoly" , "dev@dpdk.org" , "Ananyev, Konstantin" To: "Van Haaren, Harry" , Thomas Monjalon Return-path: Received: from mga06.intel.com (mga06.intel.com [134.134.136.31]) by dpdk.org (Postfix) with ESMTP id ECFC32BA5 for ; Wed, 28 Mar 2018 10:55:11 +0200 (CEST) In-Reply-To: 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 and Harry, On 3/28/2018 4:22 PM, Van Haaren, Harry wrote: >> From: Thomas Monjalon [mailto:thomas@monjalon.net] >> Sent: Wednesday, March 28, 2018 8:30 AM >> To: Tan, Jianfeng >> Cc: Burakov, Anatoly ; dev@dpdk.org; Ananyev, >> Konstantin ; Van Haaren, Harry >> >> Subject: Re: [dpdk-dev] [PATCH v6 2/2] eal: add asynchronous request API to >> DPDK IPC >> >> 28/03/2018 04:08, Tan, Jianfeng: >>> Hi Thomas , >>> >>> From: Thomas Monjalon [mailto:thomas@monjalon.net] >>>> 27/03/2018 15:59, Anatoly Burakov: >>>>> Under the hood, we create a separate thread to deal with replies to >>>>> asynchronous requests, that will just wait to be notified by the >>>>> main thread, or woken up on a timer. >>>> I really don't like that a library is creating a thread. >>>> We don't even know where the thread is created (which core). >>>> Can it be a rte_service? or in the interrupt thread? >>> Agree that we'd better not adding so many threads in a library. >>> >>> I was considering to merge all the threads into the interrupt thread, >> however, we don't have an interrupt thread in freebsd. Further, we don't >> implement alarm API in freebsd. That's why I tend to current implementation, >> and optimize it later. >> >> I would prefer we improve the current code now instead of polluting more >> with more uncontrolled threads. >> >>> For rte_service, it may be not a good idea to reply on it as it needs >> explicit API calls to setup. >> >> I don't see the issue of the explicit API. >> The IPC is a new service. My concern is that not every DPDK application sets up rte_service, but IPC will be used for very fundamental functions, like memory allocation. We could not possibly ask all DPDK applications to add rte_service now. And also take Harry's comments below into consideration, most likely, we will move these threads into interrupt thread now by adding > Although I do like to see new services, if we want to enable "core" dpdk functionality with Services, we need a proper designed solution for that. Service cores is not intended for "occasional" work - there is no method to block and sleep on a specific service until work becomes available, so this would imply a busy-polling. Using a service (hence busy polling) for rte_malloc()-based memory mapping requests is inefficient, and total overkill :) > > For this patch I suggest to use some blocking-read capable mechanism. The problem here is that we add too many threads; blocking-read does not decrease # of threads. > > The above said, in the longer term it would be good to have a design that allows new file-descriptors to be added to a "dpdk core" thread, which performs occasional lengthy work if the FD has data available. Interrupt thread vs rte_service, which is the direction to go? We actually have some others threads, in vhost and even virtio-user; we can also avoid those threads if we have a clear direction. Thanks, Jianfeng