From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Clark, Gilbert" Subject: Re: Getting started - sanity check Date: Sun, 10 May 2015 01:29:49 +0000 Message-ID: <1431221388952.74@ohio.edu> References: <1431188832058.4524@ohio.edu>, Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Cc: "dev@dpdk.org" To: "Wiles, Keith" Return-path: Received: from na01-by2-obe.outbound.protection.outlook.com (mail-by2on0106.outbound.protection.outlook.com [207.46.100.106]) by dpdk.org (Postfix) with ESMTP id 852859A87 for ; Sun, 10 May 2015 03:29:52 +0200 (CEST) In-Reply-To: Content-Language: en-US List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" Thanks for the note! I'll take another look at it. Cheers, Gilbert ________________________________________ From: Wiles, Keith Sent: Saturday, May 9, 2015 12:41 PM To: Clark, Gilbert Cc: dev@dpdk.org Subject: Re: [dpdk-dev] Getting started - sanity check Sent from my iPhone > On May 9, 2015, at 9:27 AM, Clark, Gilbert wrote: > > > Hi folks: > > I'm brand new to DPDK. Read about it off and on occasionally, but never = had the chance to sit down and play with things until now. It's been fun s= o far: just been working on a few toy applications to get myself started. > > I have run into a question, though: when calling rte_eth_tx_burst with a = ring-backed PMD I've set up, the mbufs I've sent never seem to be freed. T= his seems to make some degree of sense, but ... since I'm new, and because = the documentation says rte_eth_tx_burst should eventually free mbufs that a= re sent [1], I wanted to make sure I'm on track and not just misunderstandi= ng the way something works [2]. The mbufs are free as needed or when a watermark is hit in the driver. One = other thing I found is you need to send enough packets to hit the water mar= k for the tx mbufs start to get freed. Also you have to have enough mbufs a= llocated to hit these watermarks. I just pick two times the ring size just = to be safe. Hope that helps. > > Thanks, > Gilbert Clark > > [1] From http://dpdk.org/doc/api/rte__ethdev_8h.html : > > It is the responsibility of the rte_eth_tx_burst() function to transparen= tly free the memory buffers of packets previously sent > > [2] From lib/librte_pmd_ring.c: > > static uint16_t > eth_ring_tx(void *q, struct rte_mbuf **bufs, uint16_t nb_bufs) > { > void **ptrs =3D (void *)&bufs[0]; > struct ring_queue *r =3D q; > const uint16_t nb_tx =3D (uint16_t)rte_ring_enqueue_burst(r->rng, > ptrs, nb_bufs); > if (r->rng->flags & RING_F_SP_ENQ) { > r->tx_pkts.cnt +=3D nb_tx; > r->err_pkts.cnt +=3D nb_bufs - nb_tx; > } else { > rte_atomic64_add(&(r->tx_pkts), nb_tx); > rte_atomic64_add(&(r->err_pkts), nb_bufs - nb_tx); > } > return nb_tx; > } > > This doesn't ever appear to free a transmitted mbuf ... unless there's co= de to do that somewhere else that I'm missing?