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Date:   Tue, 18 Jul 2023 14:45:52 +0800
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Subject: Re: [PATCH net-next V2 3/4] virtio_net: support per queue interrupt
 coalesce command
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To:     Heng Qi <hengqi@linux.alibaba.com>
Cc:     gavi@nvidia.com, virtualization@lists.linux-foundation.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        bpf@vger.kernel.org, mst@redhat.com, jasowang@redhat.com,
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        edumazet@google.com, kuba@kernel.org, pabeni@redhat.com,
        ast@kernel.org, daniel@iogearbox.net, hawk@kernel.org,
        john.fastabend@gmail.com, jiri@nvidia.com, dtatulea@nvidia.com
References: <20230717143037.21858-1-gavinl@nvidia.com>
 <20230717143037.21858-4-gavinl@nvidia.com>
 <f88ad438-fb63-beeb-b999-94fb3a75d93d@linux.alibaba.com>
From:   Gavin Li <gavinl@nvidia.com>
In-Reply-To: <f88ad438-fb63-beeb-b999-94fb3a75d93d@linux.alibaba.com>
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On 7/18/2023 11:37 AM, Heng Qi wrote:
> 
> 
> 在 2023/7/17 下午10:30, Gavin Li 写道:
>> Add interrupt_coalesce config in send_queue and receive_queue to cache 
>> user
>> config.
>>
>> Send per virtqueue interrupt moderation config to underline device in 
>> order
>> to have more efficient interrupt moderation and cpu utilization of guest
>> VM.
>>
>> Signed-off-by: Gavin Li <gavinl@nvidia.com>
>> Reviewed-by: Dragos Tatulea <dtatulea@nvidia.com>
>> Reviewed-by: Jiri Pirko <jiri@nvidia.com>
>> Acked-by: Michael S. Tsirkin <mst@redhat.com>
>> ---
>>   drivers/net/virtio_net.c        | 123 ++++++++++++++++++++++++++++----
>>   include/uapi/linux/virtio_net.h |  14 ++++
>>   2 files changed, 125 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index 802ed21453f5..1566c7de9436 100644
>> --- a/drivers/net/virtio_net.c
>> +++ b/drivers/net/virtio_net.c
>> @@ -144,6 +144,8 @@ struct send_queue {
>>       struct virtnet_sq_stats stats;
>> +    struct virtnet_interrupt_coalesce intr_coal;
>> +
>>       struct napi_struct napi;
>>       /* Record whether sq is in reset state. */
>> @@ -161,6 +163,8 @@ struct receive_queue {
>>       struct virtnet_rq_stats stats;
>> +    struct virtnet_interrupt_coalesce intr_coal;
>> +
>>       /* Chain pages by the private ptr. */
>>       struct page *pages;
>> @@ -3078,6 +3082,59 @@ static int virtnet_send_notf_coal_cmds(struct 
>> virtnet_info *vi,
>>       return 0;
>>   }
>> +static int virtnet_send_ctrl_coal_vq_cmd(struct virtnet_info *vi,
>> +                     u16 vqn, u32 max_usecs, u32 max_packets)
>> +{
>> +    struct virtio_net_ctrl_coal_vq *coal_vq;
>> +    struct scatterlist sgs;
>> +
>> +    coal_vq = kzalloc(sizeof(*coal_vq), GFP_KERNEL);
>> +    if (!coal_vq)
>> +        return -ENOMEM;
>> +    coal_vq->vqn = cpu_to_le16(vqn);
>> +    coal_vq->coal.max_usecs = cpu_to_le32(max_usecs);
>> +    coal_vq->coal.max_packets = cpu_to_le32(max_packets);
>> +    sg_init_one(&sgs, coal_vq, sizeof(*coal_vq));
>> +
>> +    if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_NOTF_COAL,
>> +                  VIRTIO_NET_CTRL_NOTF_COAL_VQ_SET,
>> +                  &sgs))
>> +        return -EINVAL;
>> +
>> +    return 0;
>> +}
>> +
>> +static int virtnet_send_notf_coal_vq_cmds(struct virtnet_info *vi,
>> +                      struct ethtool_coalesce *ec,
>> +                      u16 queue)
>> +{
>> +    int err;
>> +
>> +    if (ec->rx_coalesce_usecs || ec->rx_max_coalesced_frames) {
>> +        err = virtnet_send_ctrl_coal_vq_cmd(vi, rxq2vq(queue),
>> +                            ec->rx_coalesce_usecs,
>> +                            ec->rx_max_coalesced_frames);
>> +        if (err)
>> +            return err;
>> +        /* Save parameters */
>> +        vi->rq[queue].intr_coal.max_usecs = ec->rx_coalesce_usecs;
>> +        vi->rq[queue].intr_coal.max_packets = 
>> ec->rx_max_coalesced_frames;
>> +    }
>> +
>> +    if (ec->tx_coalesce_usecs || ec->tx_max_coalesced_frames) {
>> +        err = virtnet_send_ctrl_coal_vq_cmd(vi, txq2vq(queue),
>> +                            ec->tx_coalesce_usecs,
>> +                            ec->tx_max_coalesced_frames);
>> +        if (err)
>> +            return err;
>> +        /* Save parameters */
>> +        vi->sq[queue].intr_coal.max_usecs = ec->tx_coalesce_usecs;
>> +        vi->sq[queue].intr_coal.max_packets = 
>> ec->tx_max_coalesced_frames;
>> +    }
>> +
>> +    return 0;
>> +}
>> +
>>   static int virtnet_coal_params_supported(struct ethtool_coalesce *ec)
>>   {
>>       /* usecs coalescing is supported only if VIRTIO_NET_F_NOTF_COAL
>> @@ -3094,23 +3151,39 @@ static int 
>> virtnet_coal_params_supported(struct ethtool_coalesce *ec)
>>   }
>>   static int virtnet_set_coalesce_one(struct net_device *dev,
>> -                    struct ethtool_coalesce *ec)
>> +                    struct ethtool_coalesce *ec,
>> +                    bool per_queue,
>> +                    u32 queue)
>>   {
>>       struct virtnet_info *vi = netdev_priv(dev);
>> -    int ret, i, napi_weight;
>> +    int queue_count = per_queue ? 1 : vi->max_queue_pairs;
>> +    int queue_number = per_queue ? queue : 0;
>>       bool update_napi = false;
>> +    int ret, i, napi_weight;
>> +
>> +    if (queue >= vi->max_queue_pairs)
>> +        return -EINVAL;
>>       /* Can't change NAPI weight if the link is up */
>>       napi_weight = ec->tx_max_coalesced_frames ? NAPI_POLL_WEIGHT : 0;
>> -    if (napi_weight ^ vi->sq[0].napi.weight) {
>> -        if (dev->flags & IFF_UP)
>> -            return -EBUSY;
>> -        else
>> +    for (i = queue_number; i < queue_count; i++) {
>> +        if (napi_weight ^ vi->sq[i].napi.weight) {
>> +            if (dev->flags & IFF_UP)
>> +                return -EBUSY;
>> +
>>               update_napi = true;
>> +            /* All queues that belong to [queue_number, queue_count] 
>> will be
>> +             * updated for the sake of simplicity, which might not be 
>> necessary
>> +             */
>> +            queue_number = i;
>> +            break;
>> +        }
>>       }
>> -    if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_NOTF_COAL))
>> +    if (!per_queue && virtio_has_feature(vi->vdev, 
>> VIRTIO_NET_F_NOTF_COAL))
>>           ret = virtnet_send_notf_coal_cmds(vi, ec);
>> +    else if (per_queue && virtio_has_feature(vi->vdev, 
>> VIRTIO_NET_F_VQ_NOTF_COAL))
>> +        ret = virtnet_send_notf_coal_vq_cmds(vi, ec, queue);
>>       else
>>           ret = virtnet_coal_params_supported(ec);
>> @@ -3118,7 +3191,7 @@ static int virtnet_set_coalesce_one(struct 
>> net_device *dev,
>>           return ret;
>>       if (update_napi) {
>> -        for (i = 0; i < vi->max_queue_pairs; i++)
>> +        for (i = queue_number; i < queue_count; i++)
>>               vi->sq[i].napi.weight = napi_weight;
>>       }
>> @@ -3130,19 +3203,29 @@ static int virtnet_set_coalesce(struct 
>> net_device *dev,
>>                   struct kernel_ethtool_coalesce *kernel_coal,
>>                   struct netlink_ext_ack *extack)
>>   {
>> -    return virtnet_set_coalesce_one(dev, ec);
>> +    return virtnet_set_coalesce_one(dev, ec, false, 0);
>>   }
>>   static int virtnet_get_coalesce_one(struct net_device *dev,
>> -                    struct ethtool_coalesce *ec)
>> +                    struct ethtool_coalesce *ec,
>> +                    bool per_queue,
>> +                    u32 queue)
>>   {
>>       struct virtnet_info *vi = netdev_priv(dev);
>> -    if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_NOTF_COAL)) {
>> +    if (queue >= vi->max_queue_pairs)
>> +        return -EINVAL;
>> +
>> +    if (!per_queue && virtio_has_feature(vi->vdev, 
>> VIRTIO_NET_F_NOTF_COAL)) {
>>           ec->rx_coalesce_usecs = vi->intr_coal_rx.max_usecs;
>>           ec->tx_coalesce_usecs = vi->intr_coal_tx.max_usecs;
>>           ec->tx_max_coalesced_frames = vi->intr_coal_tx.max_packets;
>>           ec->rx_max_coalesced_frames = vi->intr_coal_rx.max_packets;
>> +    } else if (per_queue && virtio_has_feature(vi->vdev, 
>> VIRTIO_NET_F_VQ_NOTF_COAL)) {
>> +        ec->rx_coalesce_usecs = vi->rq[queue].intr_coal.max_usecs;
>> +        ec->tx_coalesce_usecs = vi->sq[queue].intr_coal.max_usecs;
>> +        ec->tx_max_coalesced_frames = 
>> vi->sq[queue].intr_coal.max_packets;
>> +        ec->rx_max_coalesced_frames = 
>> vi->rq[queue].intr_coal.max_packets;
>>       } else {
>>           ec->rx_max_coalesced_frames = 1;
>> @@ -3158,7 +3241,21 @@ static int virtnet_get_coalesce(struct 
>> net_device *dev,
>>                   struct kernel_ethtool_coalesce *kernel_coal,
>>                   struct netlink_ext_ack *extack)
>>   {
>> -    return virtnet_get_coalesce_one(dev, ec);
>> +    return virtnet_get_coalesce_one(dev, ec, false, 0);
>> +}
>> +
>> +static int virtnet_set_per_queue_coalesce(struct net_device *dev,
>> +                      u32 queue,
>> +                      struct ethtool_coalesce *ec)
> 
> When \field{max_virtqueue_pairs} is the maximum value, and the user does 
> not carry the queue_mask for 'ethtool -Q',
> we will send same command for all vqs, and the device will receive a 
> large number of the same VIRTIO_NET_CTRL_NOTF_COAL_VQ_SET commands at 
> this time.
> Do we want to alleviate this situation?
> 
> Thanks.
> 

May it be better to handle this senario in ethtool user space and call 
set_coalesce instead of set_per_queue_coalesce? I'm not sure.
>> +{
>> +    return virtnet_set_coalesce_one(dev, ec, true, queue);
>> +}
>> +
>> +static int virtnet_get_per_queue_coalesce(struct net_device *dev,
>> +                      u32 queue,
>> +                      struct ethtool_coalesce *ec)
>> +{
>> +    return virtnet_get_coalesce_one(dev, ec, true, queue);
>>   }
>>   static void virtnet_init_settings(struct net_device *dev)
>> @@ -3291,6 +3388,8 @@ static const struct ethtool_ops 
>> virtnet_ethtool_ops = {
>>       .set_link_ksettings = virtnet_set_link_ksettings,
>>       .set_coalesce = virtnet_set_coalesce,
>>       .get_coalesce = virtnet_get_coalesce,
>> +    .set_per_queue_coalesce = virtnet_set_per_queue_coalesce,
>> +    .get_per_queue_coalesce = virtnet_get_per_queue_coalesce,
>>       .get_rxfh_key_size = virtnet_get_rxfh_key_size,
>>       .get_rxfh_indir_size = virtnet_get_rxfh_indir_size,
>>       .get_rxfh = virtnet_get_rxfh,
>> diff --git a/include/uapi/linux/virtio_net.h 
>> b/include/uapi/linux/virtio_net.h
>> index 12c1c9699935..cc65ef0f3c3e 100644
>> --- a/include/uapi/linux/virtio_net.h
>> +++ b/include/uapi/linux/virtio_net.h
>> @@ -56,6 +56,7 @@
>>   #define VIRTIO_NET_F_MQ    22    /* Device supports Receive Flow
>>                        * Steering */
>>   #define VIRTIO_NET_F_CTRL_MAC_ADDR 23    /* Set MAC address */
>> +#define VIRTIO_NET_F_VQ_NOTF_COAL 52    /* Device supports virtqueue 
>> notification coalescing */
>>   #define VIRTIO_NET_F_NOTF_COAL    53    /* Device supports 
>> notifications coalescing */
>>   #define VIRTIO_NET_F_GUEST_USO4    54    /* Guest can handle USOv4 
>> in. */
>>   #define VIRTIO_NET_F_GUEST_USO6    55    /* Guest can handle USOv6 
>> in. */
>> @@ -391,5 +392,18 @@ struct virtio_net_ctrl_coal_rx {
>>   };
>>   #define VIRTIO_NET_CTRL_NOTF_COAL_RX_SET        1
>> +#define VIRTIO_NET_CTRL_NOTF_COAL_VQ_SET        2
>> +#define VIRTIO_NET_CTRL_NOTF_COAL_VQ_GET        3
>> +
>> +struct virtio_net_ctrl_coal {
>> +    __le32 max_packets;
>> +    __le32 max_usecs;
>> +};
>> +
>> +struct  virtio_net_ctrl_coal_vq {
>> +    __le16 vqn;
>> +    __le16 reserved;
>> +    struct virtio_net_ctrl_coal coal;
>> +};
>>   #endif /* _UAPI_LINUX_VIRTIO_NET_H */
>