From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by dpdk.org (Postfix) with ESMTP id 668832B9E; Thu, 21 Feb 2019 12:08:12 +0100 (CET) Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id B7CD6308424E; Thu, 21 Feb 2019 11:08:11 +0000 (UTC) Received: from [10.36.112.16] (ovpn-112-16.ams2.redhat.com [10.36.112.16]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 8C5E21001DD1; Thu, 21 Feb 2019 11:08:10 +0000 (UTC) To: Tiwei Bie , zhihong.wang@intel.com, dev@dpdk.org Cc: stable@dpdk.org References: <20190219105951.31046-1-tiwei.bie@intel.com> <20190219105951.31046-3-tiwei.bie@intel.com> From: Maxime Coquelin Message-ID: Date: Thu, 21 Feb 2019 12:08:08 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20190219105951.31046-3-tiwei.bie@intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.40]); Thu, 21 Feb 2019 11:08:11 +0000 (UTC) Subject: Re: [dpdk-dev] [PATCH 2/5] net/virtio: fix in-order Tx path for split ring X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 21 Feb 2019 11:08:12 -0000 On 2/19/19 11:59 AM, Tiwei Bie wrote: > When IN_ORDER feature is negotiated, device may just write out a > single used ring entry for a batch of buffers: > > """ > Some devices always use descriptors in the same order in which they > have been made available. These devices can offer the VIRTIO_F_IN_ORDER > feature. If negotiated, this knowledge allows devices to notify the > use of a batch of buffers to the driver by only writing out a single > used ring entry with the id corresponding to the head entry of the > descriptor chain describing the last buffer in the batch. > > The device then skips forward in the ring according to the size of > the batch. Accordingly, it increments the used idx by the size of > the batch. > > The driver needs to look up the used id and calculate the batch size > to be able to advance to where the next used ring entry will be written > by the device. > """ > > Currently, the in-order Tx path in split ring can't handle this. > With this patch, driver will allocate desc_extra[] based on the > index in avail/used ring instead of the index in descriptor table. > And driver can just relay on the used->idx written by device to > reclaim the descriptors and Tx buffers. > > Fixes: e5f456a98d3c ("net/virtio: support in-order Rx and Tx") > Cc: stable@dpdk.org > > Signed-off-by: Tiwei Bie > --- > drivers/net/virtio/virtio_rxtx.c | 28 ++++++++++------------------ > 1 file changed, 10 insertions(+), 18 deletions(-) > Reviewed-by: Maxime Coquelin Thanks, Maxime