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Message-ID: <b87c060f-efec-4efe-a03d-a42242d6cec7@linux.alibaba.com>
Date: Thu, 23 Nov 2023 16:31:59 +0800
From: Heng Qi <hengqi@...ux.alibaba.com>
To: Jason Wang <jasowang@...hat.com>
Cc: netdev@...r.kernel.org, virtualization@...ts.linux-foundation.org,
mst@...hat.com, kuba@...nel.org, edumazet@...gle.com, pabeni@...hat.com,
davem@...emloft.net, hawk@...nel.org, john.fastabend@...il.com,
ast@...nel.org, horms@...nel.org, xuanzhuo@...ux.alibaba.com
Subject: Re: [PATCH net-next v4 4/4] virtio-net: support rx netdim
在 2023/11/22 下午1:52, Jason Wang 写道:
> On Mon, Nov 20, 2023 at 8:38 PM Heng Qi <hengqi@...ux.alibaba.com> wrote:
>> By comparing the traffic information in the complete napi processes,
>> let the virtio-net driver automatically adjust the coalescing
>> moderation parameters of each receive queue.
>>
>> Signed-off-by: Heng Qi <hengqi@...ux.alibaba.com>
>> ---
>> v2->v3:
>> - Some minor modifications.
>>
>> v1->v2:
>> - Improved the judgment of dim switch conditions.
>> - Cancel the work when vq reset.
>>
>> drivers/net/virtio_net.c | 191 ++++++++++++++++++++++++++++++++++-----
>> 1 file changed, 169 insertions(+), 22 deletions(-)
>>
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index 69fe09e99b3c..bc32d5aae005 100644
>> --- a/drivers/net/virtio_net.c
>> +++ b/drivers/net/virtio_net.c
>> @@ -19,6 +19,7 @@
>> #include <linux/average.h>
>> #include <linux/filter.h>
>> #include <linux/kernel.h>
>> +#include <linux/dim.h>
>> #include <net/route.h>
>> #include <net/xdp.h>
>> #include <net/net_failover.h>
>> @@ -172,6 +173,17 @@ struct receive_queue {
>>
>> struct virtnet_rq_stats stats;
>>
>> + /* The number of rx notifications */
>> + u16 calls;
>> +
>> + /* Is dynamic interrupt moderation enabled? */
>> + bool dim_enabled;
>> +
>> + /* Dynamic Interrupt Moderation */
>> + struct dim dim;
>> +
>> + u32 packets_in_napi;
>> +
>> struct virtnet_interrupt_coalesce intr_coal;
>>
>> /* Chain pages by the private ptr. */
>> @@ -305,6 +317,9 @@ struct virtnet_info {
>> u8 duplex;
>> u32 speed;
>>
>> + /* Is rx dynamic interrupt moderation enabled? */
>> + bool rx_dim_enabled;
>> +
>> /* Interrupt coalescing settings */
>> struct virtnet_interrupt_coalesce intr_coal_tx;
>> struct virtnet_interrupt_coalesce intr_coal_rx;
>> @@ -2001,6 +2016,7 @@ static void skb_recv_done(struct virtqueue *rvq)
>> struct virtnet_info *vi = rvq->vdev->priv;
>> struct receive_queue *rq = &vi->rq[vq2rxq(rvq)];
>>
>> + rq->calls++;
>> virtqueue_napi_schedule(&rq->napi, rvq);
>> }
>>
>> @@ -2141,6 +2157,26 @@ static void virtnet_poll_cleantx(struct receive_queue *rq)
>> }
>> }
>>
>> +static void virtnet_rx_dim_work(struct work_struct *work);
>> +
>> +static void virtnet_rx_dim_update(struct virtnet_info *vi, struct receive_queue *rq)
>> +{
>> + struct dim_sample cur_sample = {};
>> +
>> + if (!rq->packets_in_napi)
>> + return;
>> +
>> + u64_stats_update_begin(&rq->stats.syncp);
>> + dim_update_sample(rq->calls,
>> + u64_stats_read(&rq->stats.packets),
>> + u64_stats_read(&rq->stats.bytes),
>> + &cur_sample);
>> + u64_stats_update_end(&rq->stats.syncp);
>> +
>> + net_dim(&rq->dim, cur_sample);
>> + rq->packets_in_napi = 0;
>> +}
>> +
>> static int virtnet_poll(struct napi_struct *napi, int budget)
>> {
>> struct receive_queue *rq =
>> @@ -2149,17 +2185,22 @@ static int virtnet_poll(struct napi_struct *napi, int budget)
>> struct send_queue *sq;
>> unsigned int received;
>> unsigned int xdp_xmit = 0;
>> + bool napi_complete;
>>
>> virtnet_poll_cleantx(rq);
>>
>> received = virtnet_receive(rq, budget, &xdp_xmit);
>> + rq->packets_in_napi += received;
>>
>> if (xdp_xmit & VIRTIO_XDP_REDIR)
>> xdp_do_flush();
>>
>> /* Out of packets? */
>> - if (received < budget)
>> - virtqueue_napi_complete(napi, rq->vq, received);
>> + if (received < budget) {
>> + napi_complete = virtqueue_napi_complete(napi, rq->vq, received);
>> + if (napi_complete && rq->dim_enabled)
>> + virtnet_rx_dim_update(vi, rq);
>> + }
>>
>> if (xdp_xmit & VIRTIO_XDP_TX) {
>> sq = virtnet_xdp_get_sq(vi);
>> @@ -2179,6 +2220,7 @@ static void virtnet_disable_queue_pair(struct virtnet_info *vi, int qp_index)
>> virtnet_napi_tx_disable(&vi->sq[qp_index].napi);
>> napi_disable(&vi->rq[qp_index].napi);
>> xdp_rxq_info_unreg(&vi->rq[qp_index].xdp_rxq);
>> + cancel_work_sync(&vi->rq[qp_index].dim.work);
>> }
>>
>> static int virtnet_enable_queue_pair(struct virtnet_info *vi, int qp_index)
>> @@ -2196,6 +2238,9 @@ static int virtnet_enable_queue_pair(struct virtnet_info *vi, int qp_index)
>> if (err < 0)
>> goto err_xdp_reg_mem_model;
>>
>> + INIT_WORK(&vi->rq[qp_index].dim.work, virtnet_rx_dim_work);
>> + vi->rq[qp_index].dim.mode = DIM_CQ_PERIOD_MODE_START_FROM_EQE;
> So in V2, you explained it can be done here but I want to know why it
> must be done here.
It is not must be done here. We can place it in probe and make sure that
INIT_WORK() is
done before napi is enabled for the first time.
So then I'll don't call INIT_WORK() every time after "napi_disable ->
napi_enable" happens,
and use the following process:
Call INIT_WORK() in the driver probe and do cancel_work() after each
related napi_disable.
This will be clearer.
Additionally, Yinjun Zhang found that cancel_work_sync() will cause a
deadlock
when ndo_stop and virtnet_rx_dim_work occurs at the same time, so
cancel_work() will be used.
>
> For example, the refill_work is initialized in alloc_queues().
>
>> +
>> virtnet_napi_enable(vi->rq[qp_index].vq, &vi->rq[qp_index].napi);
>> virtnet_napi_tx_enable(vi, vi->sq[qp_index].vq, &vi->sq[qp_index].napi);
>>
>> @@ -2393,8 +2438,10 @@ static int virtnet_rx_resize(struct virtnet_info *vi,
>>
>> qindex = rq - vi->rq;
>>
>> - if (running)
>> + if (running) {
>> napi_disable(&rq->napi);
>> + cancel_work_sync(&rq->dim.work);
>> + }
>>
>> err = virtqueue_resize(rq->vq, ring_num, virtnet_rq_free_unused_buf);
>> if (err)
>> @@ -2403,8 +2450,10 @@ static int virtnet_rx_resize(struct virtnet_info *vi,
>> if (!try_fill_recv(vi, rq, GFP_KERNEL))
>> schedule_delayed_work(&vi->refill, 0);
>>
>> - if (running)
>> + if (running) {
>> + INIT_WORK(&rq->dim.work, virtnet_rx_dim_work);
>> virtnet_napi_enable(rq->vq, &rq->napi);
>> + }
>> return err;
>> }
>>
>> @@ -3341,24 +3390,55 @@ static int virtnet_send_tx_notf_coal_cmds(struct virtnet_info *vi,
>> static int virtnet_send_rx_notf_coal_cmds(struct virtnet_info *vi,
>> struct ethtool_coalesce *ec)
>> {
>> + bool rx_ctrl_dim_on = !!ec->use_adaptive_rx_coalesce;
>> + bool update = false, switch_dim;
>> struct scatterlist sgs_rx;
>> int i;
>>
>> - vi->ctrl->coal_rx.rx_usecs = cpu_to_le32(ec->rx_coalesce_usecs);
>> - vi->ctrl->coal_rx.rx_max_packets = cpu_to_le32(ec->rx_max_coalesced_frames);
>> - sg_init_one(&sgs_rx, &vi->ctrl->coal_rx, sizeof(vi->ctrl->coal_rx));
>> -
>> - if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_NOTF_COAL,
>> - VIRTIO_NET_CTRL_NOTF_COAL_RX_SET,
>> - &sgs_rx))
>> - return -EINVAL;
>> + switch_dim = rx_ctrl_dim_on != vi->rx_dim_enabled;
>> + if (switch_dim) {
>> + if (rx_ctrl_dim_on) {
>> + if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_VQ_NOTF_COAL)) {
> So basically, I'm asking why we need to duplicate the check here?
Here is VIRTIO_NET_F_*VQ*_NOTF_COAL.
>
> E.g caller has done the check for us:
>
> if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_NOTF_COAL))
> ret = virtnet_send_notf_coal_cmds(vi, ec);
> else
> ret = virtnet_coal_params_supported(ec);
>
> ?
>
> Please also check other nested if/else, usually, too many levels of
> nesting is a hint that the logic needs to be optimized.
I will optimize this.
Thanks!
>
> Thanks
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