Hi Sugesh, Actually the new API call in DPDK is not needed. A reply by Zhiyong Yang (http://dpdk.org/ml/archives/dev/2017-September/076504.html) pointed out that an existing API call provides access to the vring data structure that contains the interrupt flag. So I will abandon the DPDK patch.
Using the existing API I have created a patch on top of Ilya's output batching v4 series that automatically enables time-based batching on ports that should benefit from it most: vhostuser(client) using virtio interrupts as well as internal ports on the Linux (or BSD) host. I still need to do careful testing that the interrupt detection works reliable. The performance should be the baseline performance of Ilya's patch. BR, Jan > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Chandran, Sugesh > Sent: Friday, 13 October, 2017 17:34 > To: Jan Scheurich <[email protected]> > Cc: [email protected] > Subject: Re: [ovs-dev] [PATCH] vhost: Expose virtio interrupt requirement on > rte_vhos API > > Hi Jan, > The DPDK changes are looks OK to me and will be useful. I am interested in > testing this patch to see the impact on performance. Are > you planning to share the changes in OVS for these APIs? > > > > > Performance tests with the OVS DPDK datapath have shown that the tx > throughput over a vhostuser port into a VM with an interrupt- > based virtio driver is limited by the overhead incurred by virtio interrupts. > The OVS PMD spends up to 30% of its cycles in system calls > kicking the eventfd. Also the core running the vCPU is heavily loaded with > generating the virtio interrupts in KVM on the host and > handling these interrupts in the virtio-net driver in the guest. This limits > the throughput to about 500-700 Kpps with a single vCPU. > > OVS is trying to address this issue by batching packets to a vhostuser port > for some time to limit the virtio interrupt frequency. With a > 50 us batching period we have measured an iperf3 throughput increase by 15% > and a PMD utilization decrease from 45% to 30%. > > On the other hand, guests using virtio PMDs do not profit from time-based tx > batching. Instead they experience a 2-3% performance > penalty and an average latency increase of 30-40 us. OVS therefore intends to > apply time-based tx batching only for vhostuser tx > queues that need to trigger virtio interrupts. > > Today this information is hidden inside the rte_vhost library and not > accessible to users of the API. This patch adds a function to the > API to query it. > > Signed-off-by: Jan Scheurich > <[email protected]<mailto:[email protected]>> > > --- > > lib/librte_vhost/rte_vhost.h | 12 ++++++++++++ > lib/librte_vhost/vhost.c | 19 +++++++++++++++++++ > 2 files changed, 31 insertions(+) > > diff --git a/lib/librte_vhost/rte_vhost.h b/lib/librte_vhost/rte_vhost.h > index 8c974eb..d62338b 100644 > --- a/lib/librte_vhost/rte_vhost.h > +++ b/lib/librte_vhost/rte_vhost.h > @@ -444,6 +444,18 @@ int rte_vhost_get_vhost_vring(int vid, uint16_t > vring_idx, > */ > uint32_t rte_vhost_rx_queue_count(int vid, uint16_t qid); > > +/** > + * Does the virtio driver request interrupts for a vhost tx queue? > + * > + * @param vid > + * vhost device ID > + * @param qid > + * virtio queue index in mq case > + * @return > + * 1 if true, 0 if false > + */ > +int rte_vhost_tx_interrupt_requested(int vid, uint16_t qid); > + > #ifdef __cplusplus > } > #endif > diff --git a/lib/librte_vhost/vhost.c b/lib/librte_vhost/vhost.c > index 0b6aa1c..bd1ebf9 100644 > --- a/lib/librte_vhost/vhost.c > +++ b/lib/librte_vhost/vhost.c > @@ -503,3 +503,22 @@ struct virtio_net * > > return *((volatile uint16_t *)&vq->avail->idx) - vq->last_avail_idx; > } > + > +int rte_vhost_tx_interrupt_requested(int vid, uint16_t qid) > +{ > + struct virtio_net *dev; > + struct vhost_virtqueue *vq; > + > + dev = get_device(vid); > + if (dev == NULL) > + return 0; > + > + vq = dev->virtqueue[qid]; > + if (vq == NULL) > + return 0; > + > + if (unlikely(vq->enabled == 0 || vq->avail == NULL)) > + return 0; > + > + return !(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT); > +} > > _______________________________________________ > dev mailing list > [email protected]<mailto:[email protected]> > https://mail.openvswitch.org/mailman/listinfo/ovs-dev > > _______________________________________________ > dev mailing list > [email protected] > https://mail.openvswitch.org/mailman/listinfo/ovs-dev _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
