From: Stephen Hemminger <stephen@networkplumber.org>
To: Jan Scheurich <jan.scheurich@ericsson.com>
Cc: dev@dpdk.org, dev@openvswitch.org
Subject: Re: [dpdk-dev] [PATCH] vhost: Expose virtio interrupt requirement on rte_vhos API
Date: Sun, 24 Sep 2017 07:02:25 -0700 [thread overview]
Message-ID: <CAOaVG14gM4x7HKeYzyZ0bkvL_yAVLF+9AUufBd1eufKRs9U84A@mail.gmail.com> (raw)
In-Reply-To: <CFF8EF42F1132E4CBE2BF0AB6C21C58D78817630@ESESSMB107.ericsson.se>
I heard Fd.io has a faster vhost driver. Has anyone investigated?
On Sep 23, 2017 8:16 PM, "Jan Scheurich" <jan.scheurich@ericsson.com> wrote:
> 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 <jan.scheurich@ericsson.com>
>
> ---
>
> 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);
> +}
>
>
next prev parent reply other threads:[~2017-09-24 14:02 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-23 19:16 Jan Scheurich
2017-09-24 14:02 ` Stephen Hemminger [this message]
2017-09-25 6:49 ` Yang, Zhiyong
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