From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.droids-corp.org (zoll.droids-corp.org [94.23.50.67]) by dpdk.org (Postfix) with ESMTP id 086276893 for ; Mon, 21 Nov 2016 16:06:38 +0100 (CET) Received: from lfbn-1-5996-232.w90-110.abo.wanadoo.fr ([90.110.195.232] helo=[192.168.1.13]) by mail.droids-corp.org with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.84_2) (envelope-from ) id 1c8qEU-0007UQ-96; Mon, 21 Nov 2016 16:10:10 +0100 To: "Wiles, Keith" , "Damjan Marion (damarion)" References: <7E8AE555-F016-4F33-B046-A5DA86F493F3@cisco.com> <27853C4C-2482-49E0-8F60-178473276CF5@intel.com> Cc: "dev@dpdk.org" From: Olivier Matz Message-ID: Date: Mon, 21 Nov 2016 16:06:32 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Icedove/45.4.0 MIME-Version: 1.0 In-Reply-To: <27853C4C-2482-49E0-8F60-178473276CF5@intel.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Subject: Re: [dpdk-dev] Adding API to force freeing consumed buffers in TX ring X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 21 Nov 2016 15:06:39 -0000 Hi, On 11/21/2016 03:33 PM, Wiles, Keith wrote: > >> On Nov 21, 2016, at 4:48 AM, Damjan Marion (damarion) wrote: >> >> >> Hi, >> >> Currently in VPP we do memcpy of whole packet when we need to do >> replication as we cannot know if specific buffer is transmitted >> from tx ring before we update it again (i.e. l2 header rewrite). >> >> Unless there is already a way to address this issue in DPDK which I’m not aware >> of my proposal is that we provide mechanism for polling TX ring >> for consumed buffers. This can be either completely new API or >> extension of rte_etx_tx_burst (i.e. special case when nb_pkts=0). >> >> This will allows us to start polling tx ring when we expect some >> mbuf back, instead of waiting for next tx burst (which we don’t know >> when it will happen) and hoping that we will reach free_threshold soon. > > +1 > > In Pktgen I have the problem of not being able to reclaim all of the TX mbufs to update them for the next set of packets to send. I know this is not a common case, but I do see the case where the application needs its mbufs freed off the TX ring. Currently you need to have at least a TX ring size of mbufs on hand to make sure you can send to a TX ring. If you allocate too few you run into a deadlock case as the number of mbufs on a TX ring does not hit the flush mark. If you are sending to multiple TX rings on the same numa node from the a single TX pool you have to understand the total number of mbufs you need to have allocated to hit the TX flush on each ring. Not a clean way to handle the problems as you may have limited memory or require some logic to add more mbufs for dynamic ports. > > Anyway it would be great to require a way to clean up the TX done ring, using nb_pkts == 0 is the simplest way, but a new API is fine too. >> >> Any thoughts? Yes, it looks useful to have a such API. I would prefer another function instead of diverting the meaning of nb_pkts. Maybe this? void rte_eth_tx_free_bufs(uint8_t port_id, uint16_t queue_id); Regards, Olivier