From mboxrd@z Thu Jan 1 00:00:00 1970 From: Maxime Coquelin Subject: Re: [PATCH 2/5] net/virtio: fix in-order Tx path for split ring Date: Thu, 21 Feb 2019 12:08:08 +0100 Message-ID: References: <20190219105951.31046-1-tiwei.bie@intel.com> <20190219105951.31046-3-tiwei.bie@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Cc: stable@dpdk.org To: Tiwei Bie , zhihong.wang@intel.com, dev@dpdk.org Return-path: In-Reply-To: <20190219105951.31046-3-tiwei.bie@intel.com> 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" 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