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Message-ID: <20240225032330-mutt-send-email-mst@kernel.org>
Date: Sun, 25 Feb 2024 03:38:48 -0500
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Cc: virtualization@...ts.linux.dev, Richard Weinberger <richard@....at>,
Anton Ivanov <anton.ivanov@...bridgegreys.com>,
Johannes Berg <johannes@...solutions.net>,
Jason Wang <jasowang@...hat.com>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
Hans de Goede <hdegoede@...hat.com>,
Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
Vadim Pasternak <vadimp@...dia.com>,
Bjorn Andersson <andersson@...nel.org>,
Mathieu Poirier <mathieu.poirier@...aro.org>,
Cornelia Huck <cohuck@...hat.com>,
Halil Pasic <pasic@...ux.ibm.com>,
Eric Farman <farman@...ux.ibm.com>,
Heiko Carstens <hca@...ux.ibm.com>,
Vasily Gorbik <gor@...ux.ibm.com>,
Alexander Gordeev <agordeev@...ux.ibm.com>,
Christian Borntraeger <borntraeger@...ux.ibm.com>,
Sven Schnelle <svens@...ux.ibm.com>,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Jesper Dangaard Brouer <hawk@...nel.org>,
John Fastabend <john.fastabend@...il.com>,
linux-um@...ts.infradead.org, netdev@...r.kernel.org,
platform-driver-x86@...r.kernel.org,
linux-remoteproc@...r.kernel.org, linux-s390@...r.kernel.org,
kvm@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH vhost v2 19/19] virtio_net: sq support premapped mode
On Fri, Feb 23, 2024 at 04:27:26PM +0800, Xuan Zhuo wrote:
> If the xsk is enabling, the xsk tx will share the send queue.
> But the xsk requires that the send queue use the premapped mode.
> So the send queue must support premapped mode.
>
> cmd:
> sh samples/pktgen/pktgen_sample01_simple.sh -i eth0 \
> -s 16 -d 10.0.0.128 -m 00:16:3e:2c:c8:2e -n 0 -p 100
> CPU:
> Intel(R) Xeon(R) Platinum 8369B CPU @ 2.70GHz
>
> Machine:
> ecs.g7.2xlarge(Aliyun)
>
> before: 1600010.00
> after(no-premapped): 1599966.00
> after(premapped): 1600014.00
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> ---
> drivers/net/virtio_net.c | 136 +++++++++++++++++++++++++++++++++++++--
> 1 file changed, 132 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 7715bb7032ec..b83ef6afc4fb 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -146,6 +146,25 @@ struct virtnet_rq_dma {
> u16 need_sync;
> };
>
> +struct virtnet_sq_dma {
> + union {
> + struct virtnet_sq_dma *next;
> + void *data;
> + };
> +
> + u32 num;
> +
> + dma_addr_t addr[MAX_SKB_FRAGS + 2];
> + u32 len[MAX_SKB_FRAGS + 2];
> +};
> +
> +struct virtnet_sq_dma_head {
> + /* record for kfree */
> + void *p;
> +
> + struct virtnet_sq_dma *free;
> +};
> +
> /* Internal representation of a send virtqueue */
> struct send_queue {
> /* Virtqueue associated with this send _queue */
> @@ -165,6 +184,8 @@ struct send_queue {
>
> /* Record whether sq is in reset state. */
> bool reset;
> +
> + struct virtnet_sq_dma_head dmainfo;
> };
>
> /* Internal representation of a receive virtqueue */
> @@ -368,6 +389,95 @@ static struct xdp_frame *ptr_to_xdp(void *ptr)
> return (struct xdp_frame *)((unsigned long)ptr & ~VIRTIO_XDP_FLAG);
> }
>
> +static struct virtnet_sq_dma *virtnet_sq_unmap(struct send_queue *sq, void **data)
> +{
> + struct virtnet_sq_dma *d;
> + int i;
> +
> + d = *data;
> + *data = d->data;
> +
> + for (i = 0; i < d->num; ++i)
> + virtqueue_dma_unmap_page_attrs(sq->vq, d->addr[i], d->len[i],
> + DMA_TO_DEVICE, 0);
> +
> + d->next = sq->dmainfo.free;
> + sq->dmainfo.free = d;
> +
> + return d;
> +}
> +
> +static struct virtnet_sq_dma *virtnet_sq_map_sg(struct send_queue *sq,
> + int nents, void *data)
> +{
> + struct virtnet_sq_dma *d;
> + struct scatterlist *sg;
> + int i;
> +
> + if (!sq->dmainfo.free)
> + return NULL;
> +
> + d = sq->dmainfo.free;
> + sq->dmainfo.free = d->next;
> +
> + for_each_sg(sq->sg, sg, nents, i) {
> + if (virtqueue_dma_map_sg_attrs(sq->vq, sg, DMA_TO_DEVICE, 0))
> + goto err;
> +
> + d->addr[i] = sg->dma_address;
> + d->len[i] = sg->length;
> + }
> +
> + d->data = data;
> + d->num = i;
> + return d;
> +
> +err:
> + d->num = i;
> + virtnet_sq_unmap(sq, (void **)&d);
> + return NULL;
> +}
Do I see a reimplementation of linux/llist.h here?
> +
> +static int virtnet_add_outbuf(struct send_queue *sq, u32 num, void *data)
> +{
> + int ret;
> +
> + if (sq->vq->premapped) {
> + data = virtnet_sq_map_sg(sq, num, data);
> + if (!data)
> + return -ENOMEM;
> + }
> +
> + ret = virtqueue_add_outbuf(sq->vq, sq->sg, num, data, GFP_ATOMIC);
> + if (ret && sq->vq->premapped)
> + virtnet_sq_unmap(sq, &data);
> +
> + return ret;
> +}
> +
> +static int virtnet_sq_init_dma_mate(struct send_queue *sq)
Mate? The popular south african drink?
> +{
> + struct virtnet_sq_dma *d;
> + int num, i;
> +
> + num = virtqueue_get_vring_size(sq->vq);
> +
> + sq->dmainfo.free = kcalloc(num, sizeof(*sq->dmainfo.free), GFP_KERNEL);
> + if (!sq->dmainfo.free)
> + return -ENOMEM;
This could be quite a bit of memory for a large queue. And for a bunch
of common cases where unmap is a nop (e.g. iommu pt) this does nothing
useful at all. And also, this does nothing useful if PLATFORM_ACCESS is off
which is super common.
A while ago I proposed:
- extend DMA APIs so one can query whether unmap is a nop
and whether sync is a nop
- virtio wrapper taking into account PLATFORM_ACCESS too
then we can save all this work and memory when not needed.
> +
> + sq->dmainfo.p = sq->dmainfo.free;
> +
> + for (i = 0; i < num; ++i) {
> + d = &sq->dmainfo.free[i];
> + d->next = d + 1;
> + }
> +
> + d->next = NULL;
> +
> + return 0;
> +}
> +
> static void __free_old_xmit(struct send_queue *sq, bool in_napi,
> struct virtnet_sq_free_stats *stats)
> {
> @@ -377,6 +487,9 @@ static void __free_old_xmit(struct send_queue *sq, bool in_napi,
> while ((ptr = virtqueue_get_buf(sq->vq, &len)) != NULL) {
> ++stats->packets;
>
> + if (sq->vq->premapped)
> + virtnet_sq_unmap(sq, &ptr);
> +
> if (!is_xdp_frame(ptr)) {
> struct sk_buff *skb = ptr;
>
> @@ -890,8 +1003,7 @@ static int __virtnet_xdp_xmit_one(struct virtnet_info *vi,
> skb_frag_size(frag), skb_frag_off(frag));
> }
>
> - err = virtqueue_add_outbuf(sq->vq, sq->sg, nr_frags + 1,
> - xdp_to_ptr(xdpf), GFP_ATOMIC);
> + err = virtnet_add_outbuf(sq, nr_frags + 1, xdp_to_ptr(xdpf));
> if (unlikely(err))
> return -ENOSPC; /* Caller handle free/refcnt */
>
> @@ -2357,7 +2469,7 @@ static int xmit_skb(struct send_queue *sq, struct sk_buff *skb)
> return num_sg;
> num_sg++;
> }
> - return virtqueue_add_outbuf(sq->vq, sq->sg, num_sg, skb, GFP_ATOMIC);
> + return virtnet_add_outbuf(sq, num_sg, skb);
> }
>
> static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
> @@ -4166,6 +4278,8 @@ static void virtnet_free_queues(struct virtnet_info *vi)
> for (i = 0; i < vi->max_queue_pairs; i++) {
> __netif_napi_del(&vi->rq[i].napi);
> __netif_napi_del(&vi->sq[i].napi);
> +
> + kfree(vi->sq[i].dmainfo.p);
> }
>
> /* We called __netif_napi_del(),
> @@ -4214,6 +4328,15 @@ static void free_receive_page_frags(struct virtnet_info *vi)
>
> static void virtnet_sq_free_unused_buf(struct virtqueue *vq, void *buf)
> {
> + struct virtnet_info *vi = vq->vdev->priv;
> + struct send_queue *sq;
> + int i = vq2rxq(vq);
> +
> + sq = &vi->sq[i];
> +
> + if (sq->vq->premapped)
> + virtnet_sq_unmap(sq, &buf);
> +
> if (!is_xdp_frame(buf))
> dev_kfree_skb(buf);
> else
> @@ -4327,8 +4450,10 @@ static int virtnet_find_vqs(struct virtnet_info *vi)
> if (ctx)
> ctx[rxq2vq(i)] = true;
>
> - if (premapped)
> + if (premapped) {
> premapped[rxq2vq(i)] = true;
> + premapped[txq2vq(i)] = true;
> + }
> }
>
> cfg.nvqs = total_vqs;
> @@ -4352,6 +4477,9 @@ static int virtnet_find_vqs(struct virtnet_info *vi)
> vi->rq[i].vq = vqs[rxq2vq(i)];
> vi->rq[i].min_buf_len = mergeable_min_buf_len(vi, vi->rq[i].vq);
> vi->sq[i].vq = vqs[txq2vq(i)];
> +
> + if (vi->sq[i].vq->premapped)
> + virtnet_sq_init_dma_mate(&vi->sq[i]);
> }
>
> /* run here: ret == 0. */
> --
> 2.32.0.3.g01195cf9f
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