diff mbox series

[net-next,3/3] virtio-net: reduce the CPU consumption of dim worker

Message ID 1705410693-118895-4-git-send-email-hengqi@linux.alibaba.com (mailing list archive)
State Changes Requested
Delegated to: Netdev Maintainers
Headers show
Series virtio-net: a fix and some updates for virtio dim | expand

Checks

Context Check Description
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for net-next
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit fail Errors and warnings before: 1095 this patch: 18
netdev/cc_maintainers success CCed 0 of 0 maintainers
netdev/build_clang fail Errors and warnings before: 1108 this patch: 19
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn fail Errors and warnings before: 1112 this patch: 18
netdev/checkpatch warning WARNING: Do not crash the kernel unless it is absolutely unavoidable--use WARN_ON_ONCE() plus recovery code (if feasible) instead of BUG() or variants WARNING: Prefer 'unsigned int' to bare use of 'unsigned' WARNING: line length of 89 exceeds 80 columns WARNING: line length of 92 exceeds 80 columns WARNING: line length of 96 exceeds 80 columns WARNING: line length of 98 exceeds 80 columns
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0

Commit Message

Heng Qi Jan. 16, 2024, 1:11 p.m. UTC 
Accumulate multiple request commands to kick the device once,
and obtain the processing results of the corresponding commands
asynchronously. The batch command method is used to optimize the
CPU overhead of the DIM worker caused by the guest being busy
waiting for the command response result.

On an 8-queue device, without this patch, the guest cpu overhead
due to waiting for cvq could be 10+% and above. With this patch,
the corresponding overhead is basically invisible.

Signed-off-by: Heng Qi <hengqi@linux.alibaba.com>
---
 drivers/net/virtio_net.c | 185 ++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 158 insertions(+), 27 deletions(-)

Comments

Simon Horman Jan. 16, 2024, 7:56 p.m. UTC | #1 
On Tue, Jan 16, 2024 at 09:11:33PM +0800, Heng Qi wrote:
> Accumulate multiple request commands to kick the device once,
> and obtain the processing results of the corresponding commands
> asynchronously. The batch command method is used to optimize the
> CPU overhead of the DIM worker caused by the guest being busy
> waiting for the command response result.
> 
> On an 8-queue device, without this patch, the guest cpu overhead
> due to waiting for cvq could be 10+% and above. With this patch,
> the corresponding overhead is basically invisible.
> 
> Signed-off-by: Heng Qi <hengqi@linux.alibaba.com>

...

> @@ -3520,22 +3568,99 @@ static int virtnet_send_notf_coal_vq_cmds(struct virtnet_info *vi,
>  	return 0;
>  }
>  
> +static bool virtnet_add_dim_command(struct virtnet_info *vi,
> +				    struct virtnet_batch_coal *ctrl)
> +{
> +	struct scatterlist *sgs[4], hdr, stat, out;
> +	unsigned out_num = 0;
> +	int ret;
> +
> +	/* Caller should know better */
> +	BUG_ON(!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ));
> +
> +	ctrl->hdr.class = VIRTIO_NET_CTRL_NOTF_COAL;
> +	ctrl->hdr.cmd = VIRTIO_NET_CTRL_NOTF_COAL_VQS_SET;
> +
> +	/* Add header */
> +	sg_init_one(&hdr, &ctrl->hdr, sizeof(ctrl->hdr));
> +	sgs[out_num++] = &hdr;
> +
> +	/* Add body */
> +	sg_init_one(&out, &ctrl->num_entries, sizeof(ctrl->num_entries) +
> +		    ctrl->num_entries * sizeof(struct virtnet_coal_entry));

Hi Heng Qi,

I am a bit confused.
With this series applied on top of net-next
struct virtnet_coal_entry doesn't seem to exist.


> +	sgs[out_num++] = &out;
> +
> +	/* Add return status. */
> +	ctrl->status = VIRTIO_NET_OK;
> +	sg_init_one(&stat, &ctrl->status, sizeof(ctrl->status));
> +	sgs[out_num] = &stat;
> +
> +	BUG_ON(out_num + 1 > ARRAY_SIZE(sgs));
> +	ret = virtqueue_add_sgs(vi->cvq, sgs, out_num, 1, ctrl, GFP_ATOMIC);
> +	if (ret < 0) {
> +		dev_warn(&vi->vdev->dev, "Failed to add sgs for command vq: %d\n.", ret);
> +		return false;
> +	}
> +
> +	virtqueue_kick(vi->cvq);
> +
> +	ctrl->usable = false;
> +	vi->cvq_cmd_nums++;
> +
> +	return true;
> +}

...
Heng Qi Jan. 17, 2024, 3:41 a.m. UTC | #2 
在 2024/1/17 上午3:56, Simon Horman 写道:
> On Tue, Jan 16, 2024 at 09:11:33PM +0800, Heng Qi wrote:
>> Accumulate multiple request commands to kick the device once,
>> and obtain the processing results of the corresponding commands
>> asynchronously. The batch command method is used to optimize the
>> CPU overhead of the DIM worker caused by the guest being busy
>> waiting for the command response result.
>>
>> On an 8-queue device, without this patch, the guest cpu overhead
>> due to waiting for cvq could be 10+% and above. With this patch,
>> the corresponding overhead is basically invisible.
>>
>> Signed-off-by: Heng Qi <hengqi@linux.alibaba.com>
> ...
>
>> @@ -3520,22 +3568,99 @@ static int virtnet_send_notf_coal_vq_cmds(struct virtnet_info *vi,
>>   	return 0;
>>   }
>>   
>> +static bool virtnet_add_dim_command(struct virtnet_info *vi,
>> +				    struct virtnet_batch_coal *ctrl)
>> +{
>> +	struct scatterlist *sgs[4], hdr, stat, out;
>> +	unsigned out_num = 0;
>> +	int ret;
>> +
>> +	/* Caller should know better */
>> +	BUG_ON(!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ));
>> +
>> +	ctrl->hdr.class = VIRTIO_NET_CTRL_NOTF_COAL;
>> +	ctrl->hdr.cmd = VIRTIO_NET_CTRL_NOTF_COAL_VQS_SET;
>> +
>> +	/* Add header */
>> +	sg_init_one(&hdr, &ctrl->hdr, sizeof(ctrl->hdr));
>> +	sgs[out_num++] = &hdr;
>> +
>> +	/* Add body */
>> +	sg_init_one(&out, &ctrl->num_entries, sizeof(ctrl->num_entries) +
>> +		    ctrl->num_entries * sizeof(struct virtnet_coal_entry));
> Hi Heng Qi,
>
> I am a bit confused.
> With this series applied on top of net-next
> struct virtnet_coal_entry doesn't seem to exist.

Hi Simon,

It should be struct virtio_net_ctrl_coal_vq.

Thanks.

>
>
>> +	sgs[out_num++] = &out;
>> +
>> +	/* Add return status. */
>> +	ctrl->status = VIRTIO_NET_OK;
>> +	sg_init_one(&stat, &ctrl->status, sizeof(ctrl->status));
>> +	sgs[out_num] = &stat;
>> +
>> +	BUG_ON(out_num + 1 > ARRAY_SIZE(sgs));
>> +	ret = virtqueue_add_sgs(vi->cvq, sgs, out_num, 1, ctrl, GFP_ATOMIC);
>> +	if (ret < 0) {
>> +		dev_warn(&vi->vdev->dev, "Failed to add sgs for command vq: %d\n.", ret);
>> +		return false;
>> +	}
>> +
>> +	virtqueue_kick(vi->cvq);
>> +
>> +	ctrl->usable = false;
>> +	vi->cvq_cmd_nums++;
>> +
>> +	return true;
>> +}
> ...
kernel test robot Jan. 19, 2024, 10:31 a.m. UTC | #3 
Hi Heng,

kernel test robot noticed the following build errors:

[auto build test ERROR on net-next/main]

url:    https://github.com/intel-lab-lkp/linux/commits/Heng-Qi/virtio-net-fix-possible-dim-status-unrecoverable/20240116-211306
base:   net-next/main
patch link:    https://lore.kernel.org/r/1705410693-118895-4-git-send-email-hengqi%40linux.alibaba.com
patch subject: [PATCH net-next 3/3] virtio-net: reduce the CPU consumption of dim worker
config: i386-randconfig-012-20240119 (https://download.01.org/0day-ci/archive/20240119/202401191807.RIhMHJ4U-lkp@intel.com/config)
compiler: ClangBuiltLinux clang version 17.0.6 (https://github.com/llvm/llvm-project 6009708b4367171ccdbf4b5905cb6a803753fe18)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240119/202401191807.RIhMHJ4U-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202401191807.RIhMHJ4U-lkp@intel.com/

All errors (new ones prefixed by >>):

>> drivers/net/virtio_net.c:3590:27: error: invalid application of 'sizeof' to an incomplete type 'struct virtnet_coal_entry'
    3590 |                     ctrl->num_entries * sizeof(struct virtnet_coal_entry));
         |                                         ^     ~~~~~~~~~~~~~~~~~~~~~~~~~~~
   drivers/net/virtio_net.c:3590:41: note: forward declaration of 'struct virtnet_coal_entry'
    3590 |                     ctrl->num_entries * sizeof(struct virtnet_coal_entry));
         |                                                       ^
   drivers/net/virtio_net.c:3658:27: error: invalid application of 'sizeof' to an incomplete type 'struct virtnet_coal_entry'
    3658 |                                 vi->max_queue_pairs * sizeof(struct virtnet_coal_entry));
         |                                                       ^     ~~~~~~~~~~~~~~~~~~~~~~~~~~~
   drivers/net/virtio_net.c:3658:41: note: forward declaration of 'struct virtnet_coal_entry'
    3658 |                                 vi->max_queue_pairs * sizeof(struct virtnet_coal_entry));
         |                                                                     ^
   drivers/net/virtio_net.c:4544:31: error: invalid application of 'sizeof' to an incomplete type 'struct virtnet_coal_entry'
    4544 |                       vi->max_queue_pairs * sizeof(struct virtnet_coal_entry)), GFP_KERNEL);
         |                                             ^     ~~~~~~~~~~~~~~~~~~~~~~~~~~~
   drivers/net/virtio_net.c:4544:45: note: forward declaration of 'struct virtnet_coal_entry'
    4544 |                       vi->max_queue_pairs * sizeof(struct virtnet_coal_entry)), GFP_KERNEL);
         |                                                           ^
   drivers/net/virtio_net.c:4551:27: error: invalid application of 'sizeof' to an incomplete type 'struct virtnet_coal_entry'
    4551 |                                 vi->max_queue_pairs * sizeof(struct virtnet_coal_entry));
         |                                                       ^     ~~~~~~~~~~~~~~~~~~~~~~~~~~~
   drivers/net/virtio_net.c:4544:45: note: forward declaration of 'struct virtnet_coal_entry'
    4544 |                       vi->max_queue_pairs * sizeof(struct virtnet_coal_entry)), GFP_KERNEL);
         |                                                           ^
   4 errors generated.


vim +3590 drivers/net/virtio_net.c

  3570	
  3571	static bool virtnet_add_dim_command(struct virtnet_info *vi,
  3572					    struct virtnet_batch_coal *ctrl)
  3573	{
  3574		struct scatterlist *sgs[4], hdr, stat, out;
  3575		unsigned out_num = 0;
  3576		int ret;
  3577	
  3578		/* Caller should know better */
  3579		BUG_ON(!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ));
  3580	
  3581		ctrl->hdr.class = VIRTIO_NET_CTRL_NOTF_COAL;
  3582		ctrl->hdr.cmd = VIRTIO_NET_CTRL_NOTF_COAL_VQS_SET;
  3583	
  3584		/* Add header */
  3585		sg_init_one(&hdr, &ctrl->hdr, sizeof(ctrl->hdr));
  3586		sgs[out_num++] = &hdr;
  3587	
  3588		/* Add body */
  3589		sg_init_one(&out, &ctrl->num_entries, sizeof(ctrl->num_entries) +
> 3590			    ctrl->num_entries * sizeof(struct virtnet_coal_entry));
  3591		sgs[out_num++] = &out;
  3592	
  3593		/* Add return status. */
  3594		ctrl->status = VIRTIO_NET_OK;
  3595		sg_init_one(&stat, &ctrl->status, sizeof(ctrl->status));
  3596		sgs[out_num] = &stat;
  3597	
  3598		BUG_ON(out_num + 1 > ARRAY_SIZE(sgs));
  3599		ret = virtqueue_add_sgs(vi->cvq, sgs, out_num, 1, ctrl, GFP_ATOMIC);
  3600		if (ret < 0) {
  3601			dev_warn(&vi->vdev->dev, "Failed to add sgs for command vq: %d\n.", ret);
  3602			return false;
  3603		}
  3604	
  3605		virtqueue_kick(vi->cvq);
  3606	
  3607		ctrl->usable = false;
  3608		vi->cvq_cmd_nums++;
  3609	
  3610		return true;
  3611	}
  3612
kernel test robot Jan. 19, 2024, 1:43 p.m. UTC | #4 
Hi Heng,

kernel test robot noticed the following build errors:

[auto build test ERROR on net-next/main]

url:    https://github.com/intel-lab-lkp/linux/commits/Heng-Qi/virtio-net-fix-possible-dim-status-unrecoverable/20240116-211306
base:   net-next/main
patch link:    https://lore.kernel.org/r/1705410693-118895-4-git-send-email-hengqi%40linux.alibaba.com
patch subject: [PATCH net-next 3/3] virtio-net: reduce the CPU consumption of dim worker
config: i386-buildonly-randconfig-004-20240119 (https://download.01.org/0day-ci/archive/20240119/202401192156.ZUNUJmuA-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240119/202401192156.ZUNUJmuA-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202401192156.ZUNUJmuA-lkp@intel.com/

All errors (new ones prefixed by >>):

   drivers/net/virtio_net.c: In function 'virtnet_add_dim_command':
>> drivers/net/virtio_net.c:3590:48: error: invalid application of 'sizeof' to incomplete type 'struct virtnet_coal_entry'
    3590 |                     ctrl->num_entries * sizeof(struct virtnet_coal_entry));
         |                                                ^~~~~~
   drivers/net/virtio_net.c: In function 'virtnet_rx_dim_work':
   drivers/net/virtio_net.c:3658:62: error: invalid application of 'sizeof' to incomplete type 'struct virtnet_coal_entry'
    3658 |                                 vi->max_queue_pairs * sizeof(struct virtnet_coal_entry));
         |                                                              ^~~~~~
   drivers/net/virtio_net.c: In function 'virtnet_alloc_queues':
   drivers/net/virtio_net.c:4544:52: error: invalid application of 'sizeof' to incomplete type 'struct virtnet_coal_entry'
    4544 |                       vi->max_queue_pairs * sizeof(struct virtnet_coal_entry)), GFP_KERNEL);
         |                                                    ^~~~~~
   drivers/net/virtio_net.c:4551:62: error: invalid application of 'sizeof' to incomplete type 'struct virtnet_coal_entry'
    4551 |                                 vi->max_queue_pairs * sizeof(struct virtnet_coal_entry));
         |                                                              ^~~~~~


vim +3590 drivers/net/virtio_net.c

  3570	
  3571	static bool virtnet_add_dim_command(struct virtnet_info *vi,
  3572					    struct virtnet_batch_coal *ctrl)
  3573	{
  3574		struct scatterlist *sgs[4], hdr, stat, out;
  3575		unsigned out_num = 0;
  3576		int ret;
  3577	
  3578		/* Caller should know better */
  3579		BUG_ON(!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ));
  3580	
  3581		ctrl->hdr.class = VIRTIO_NET_CTRL_NOTF_COAL;
  3582		ctrl->hdr.cmd = VIRTIO_NET_CTRL_NOTF_COAL_VQS_SET;
  3583	
  3584		/* Add header */
  3585		sg_init_one(&hdr, &ctrl->hdr, sizeof(ctrl->hdr));
  3586		sgs[out_num++] = &hdr;
  3587	
  3588		/* Add body */
  3589		sg_init_one(&out, &ctrl->num_entries, sizeof(ctrl->num_entries) +
> 3590			    ctrl->num_entries * sizeof(struct virtnet_coal_entry));
  3591		sgs[out_num++] = &out;
  3592	
  3593		/* Add return status. */
  3594		ctrl->status = VIRTIO_NET_OK;
  3595		sg_init_one(&stat, &ctrl->status, sizeof(ctrl->status));
  3596		sgs[out_num] = &stat;
  3597	
  3598		BUG_ON(out_num + 1 > ARRAY_SIZE(sgs));
  3599		ret = virtqueue_add_sgs(vi->cvq, sgs, out_num, 1, ctrl, GFP_ATOMIC);
  3600		if (ret < 0) {
  3601			dev_warn(&vi->vdev->dev, "Failed to add sgs for command vq: %d\n.", ret);
  3602			return false;
  3603		}
  3604	
  3605		virtqueue_kick(vi->cvq);
  3606	
  3607		ctrl->usable = false;
  3608		vi->cvq_cmd_nums++;
  3609	
  3610		return true;
  3611	}
  3612
Xuan Zhuo Jan. 22, 2024, 7:19 a.m. UTC | #5 
On Tue, 16 Jan 2024 21:11:33 +0800, Heng Qi <hengqi@linux.alibaba.com> wrote:
> Accumulate multiple request commands to kick the device once,
> and obtain the processing results of the corresponding commands
> asynchronously. The batch command method is used to optimize the
> CPU overhead of the DIM worker caused by the guest being busy
> waiting for the command response result.
>
> On an 8-queue device, without this patch, the guest cpu overhead
> due to waiting for cvq could be 10+% and above. With this patch,
> the corresponding overhead is basically invisible.
>
> Signed-off-by: Heng Qi <hengqi@linux.alibaba.com>
> ---
>  drivers/net/virtio_net.c | 185 ++++++++++++++++++++++++++++++++++++++++-------
>  1 file changed, 158 insertions(+), 27 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index e4305ad..9f22c85 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -33,6 +33,8 @@
>  module_param(gso, bool, 0444);
>  module_param(napi_tx, bool, 0644);
>
> +#define BATCH_CMD 25
> +
>  /* FIXME: MTU in config. */
>  #define GOOD_PACKET_LEN (ETH_HLEN + VLAN_HLEN + ETH_DATA_LEN)
>  #define GOOD_COPY_LEN	128
> @@ -134,6 +136,9 @@ struct virtnet_interrupt_coalesce {
>  };
>
>  struct virtnet_batch_coal {
> +	struct virtio_net_ctrl_hdr hdr;
> +	virtio_net_ctrl_ack status;
> +	__u8 usable;
>  	__le32 num_entries;
>  	struct virtio_net_ctrl_coal_vq coal_vqs[];
>  };
> @@ -299,6 +304,7 @@ struct virtnet_info {
>
>  	/* Work struct for delayed refilling if we run low on memory. */
>  	struct delayed_work refill;
> +	struct delayed_work get_cvq;
>
>  	/* Is delayed refill enabled? */
>  	bool refill_enabled;
> @@ -326,6 +332,7 @@ struct virtnet_info {
>  	bool rx_dim_enabled;
>
>  	/* Interrupt coalescing settings */
> +	int cvq_cmd_nums;
>  	struct virtnet_batch_coal *batch_coal;
>  	struct virtnet_interrupt_coalesce intr_coal_tx;
>  	struct virtnet_interrupt_coalesce intr_coal_rx;
> @@ -2512,6 +2519,46 @@ static int virtnet_tx_resize(struct virtnet_info *vi,
>  	return err;
>  }
>
> +static bool virtnet_process_dim_cmd(struct virtnet_info *vi, void *res)
> +{
> +	struct virtnet_batch_coal *batch_coal;
> +	u16 queue;
> +	int i;
> +
> +	if (res != ((void *)vi)) {
> +		batch_coal = (struct virtnet_batch_coal *)res;
> +		batch_coal->usable = true;
> +		vi->cvq_cmd_nums--;
> +		for (i = 0; i < batch_coal->num_entries; i++) {
> +			queue = batch_coal->coal_vqs[i].vqn / 2;
> +			vi->rq[queue].dim.state = DIM_START_MEASURE;
> +		}
> +	} else {
> +		return true;
> +	}
> +
> +	return false;
> +}
> +
> +static bool virtnet_cvq_response(struct virtnet_info *vi, bool poll)
> +{
> +	unsigned tmp;
> +	void *res;
> +
> +	if (!poll) {
> +		while ((res = virtqueue_get_buf(vi->cvq, &tmp)) &&
> +		       !virtqueue_is_broken(vi->cvq))
> +			virtnet_process_dim_cmd(vi, res);
> +		return 0;
> +	}
> +
> +	while (!(res = virtqueue_get_buf(vi->cvq, &tmp)) &&
> +	       !virtqueue_is_broken(vi->cvq))
> +		cpu_relax();
> +
> +	return virtnet_process_dim_cmd(vi, res);


How about?

	while (true) {
		res = virtqueue_get_buf(vi->cvq, &tmp);
		if (!res) {
			if (poll) {
				if (virtqueue_is_broken(vi->cvq))
					return 0;

				cpu_relax();
				continue;
			}

			return false;
		}

		if (res == ((void *)vi))
			return true;

		virtnet_process_dim_cmd(vi, res);
	}

Thanks.



> +}
> +
>  /*
>   * Send command via the control virtqueue and check status.  Commands
>   * supported by the hypervisor, as indicated by feature bits, should
> @@ -2521,7 +2568,7 @@ static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
>  				 struct scatterlist *out)
>  {
>  	struct scatterlist *sgs[4], hdr, stat;
> -	unsigned out_num = 0, tmp;
> +	unsigned out_num = 0;
>  	int ret;
>
>  	/* Caller should know better */
> @@ -2555,9 +2602,9 @@ static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
>  	/* Spin for a response, the kick causes an ioport write, trapping
>  	 * into the hypervisor, so the request should be handled immediately.
>  	 */
> -	while (!virtqueue_get_buf(vi->cvq, &tmp) &&
> -	       !virtqueue_is_broken(vi->cvq))
> -		cpu_relax();
> +	while (true)
> +		if (virtnet_cvq_response(vi, true))
> +			break;
>
>  	return vi->ctrl->status == VIRTIO_NET_OK;
>  }
> @@ -2709,6 +2756,7 @@ static int virtnet_close(struct net_device *dev)
>  		cancel_work_sync(&vi->rq[i].dim.work);
>  	}
>
> +	cancel_delayed_work_sync(&vi->get_cvq);
>  	return 0;
>  }
>
> @@ -3520,22 +3568,99 @@ static int virtnet_send_notf_coal_vq_cmds(struct virtnet_info *vi,
>  	return 0;
>  }
>
> +static bool virtnet_add_dim_command(struct virtnet_info *vi,
> +				    struct virtnet_batch_coal *ctrl)
> +{
> +	struct scatterlist *sgs[4], hdr, stat, out;
> +	unsigned out_num = 0;
> +	int ret;
> +
> +	/* Caller should know better */
> +	BUG_ON(!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ));
> +
> +	ctrl->hdr.class = VIRTIO_NET_CTRL_NOTF_COAL;
> +	ctrl->hdr.cmd = VIRTIO_NET_CTRL_NOTF_COAL_VQS_SET;
> +
> +	/* Add header */
> +	sg_init_one(&hdr, &ctrl->hdr, sizeof(ctrl->hdr));
> +	sgs[out_num++] = &hdr;
> +
> +	/* Add body */
> +	sg_init_one(&out, &ctrl->num_entries, sizeof(ctrl->num_entries) +
> +		    ctrl->num_entries * sizeof(struct virtnet_coal_entry));
> +	sgs[out_num++] = &out;
> +
> +	/* Add return status. */
> +	ctrl->status = VIRTIO_NET_OK;
> +	sg_init_one(&stat, &ctrl->status, sizeof(ctrl->status));
> +	sgs[out_num] = &stat;
> +
> +	BUG_ON(out_num + 1 > ARRAY_SIZE(sgs));
> +	ret = virtqueue_add_sgs(vi->cvq, sgs, out_num, 1, ctrl, GFP_ATOMIC);
> +	if (ret < 0) {
> +		dev_warn(&vi->vdev->dev, "Failed to add sgs for command vq: %d\n.", ret);
> +		return false;
> +	}
> +
> +	virtqueue_kick(vi->cvq);
> +
> +	ctrl->usable = false;
> +	vi->cvq_cmd_nums++;
> +
> +	return true;
> +}
> +
> +static void get_cvq_work(struct work_struct *work)
> +{
> +	struct virtnet_info *vi =
> +		container_of(work, struct virtnet_info, get_cvq.work);
> +
> +	if (!rtnl_trylock()) {
> +		schedule_delayed_work(&vi->get_cvq, 5);
> +		return;
> +	}
> +
> +	if (!vi->cvq_cmd_nums)
> +		goto ret;
> +
> +	virtnet_cvq_response(vi, false);
> +
> +	if (vi->cvq_cmd_nums)
> +		schedule_delayed_work(&vi->get_cvq, 5);
> +
> +ret:
> +	rtnl_unlock();
> +}
> +
>  static void virtnet_rx_dim_work(struct work_struct *work)
>  {
>  	struct dim *dim = container_of(work, struct dim, work);
>  	struct receive_queue *rq = container_of(dim,
>  			struct receive_queue, dim);
>  	struct virtnet_info *vi = rq->vq->vdev->priv;
> +	struct virtnet_batch_coal *avail_coal;
>  	struct dim_cq_moder update_moder;
> -	struct virtnet_batch_coal *coal = vi->batch_coal;
> -	struct scatterlist sgs;
> -	int i, j = 0;
> +	int i, j = 0, position;
> +	u8 *buf;
>
>  	if (!rtnl_trylock()) {
>  		schedule_work(&dim->work);
>  		return;
>  	}
>
> +	if (vi->cvq_cmd_nums == BATCH_CMD || vi->cvq->num_free < 3 ||
> +	    vi->cvq->num_free <= (virtqueue_get_vring_size(vi->cvq) / 3))
> +		virtnet_cvq_response(vi, true);
> +
> +	for (i = 0; i < BATCH_CMD; i++) {
> +		buf = (u8 *)vi->batch_coal;
> +		position = i * (sizeof(struct virtnet_batch_coal) +
> +				vi->max_queue_pairs * sizeof(struct virtnet_coal_entry));
> +		avail_coal = (struct virtnet_batch_coal *)(&buf[position]);
> +		if (avail_coal->usable)
> +			break;
> +	}
> +
>  	/* Each rxq's work is queued by "net_dim()->schedule_work()"
>  	 * in response to NAPI traffic changes. Note that dim->profile_ix
>  	 * for each rxq is updated prior to the queuing action.
> @@ -3552,30 +3677,26 @@ static void virtnet_rx_dim_work(struct work_struct *work)
>  		update_moder = net_dim_get_rx_moderation(dim->mode, dim->profile_ix);
>  		if (update_moder.usec != rq->intr_coal.max_usecs ||
>  		    update_moder.pkts != rq->intr_coal.max_packets) {
> -			coal->coal_vqs[j].vqn = cpu_to_le16(rxq2vq(i));
> -			coal->coal_vqs[j].coal.max_usecs = cpu_to_le32(update_moder.usec);
> -			coal->coal_vqs[j].coal.max_packets = cpu_to_le32(update_moder.pkts);
> +			avail_coal->coal_vqs[j].vqn = cpu_to_le16(rxq2vq(i));
> +			avail_coal->coal_vqs[j].coal.max_usecs = cpu_to_le32(update_moder.usec);
> +			avail_coal->coal_vqs[j].coal.max_packets = cpu_to_le32(update_moder.pkts);
>  			rq->intr_coal.max_usecs = update_moder.usec;
>  			rq->intr_coal.max_packets = update_moder.pkts;
>  			j++;
> -		}
> +		} else if (dim->state == DIM_APPLY_NEW_PROFILE)
> +			dim->state = DIM_START_MEASURE;
>  	}
>
>  	if (!j)
>  		goto ret;
>
> -	coal->num_entries = cpu_to_le32(j);
> -	sg_init_one(&sgs, coal, sizeof(struct virtnet_batch_coal) +
> -		    j * sizeof(struct virtio_net_ctrl_coal_vq));
> -	if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_NOTF_COAL,
> -				  VIRTIO_NET_CTRL_NOTF_COAL_VQS_SET,
> -				  &sgs))
> -		dev_warn(&vi->vdev->dev, "Failed to add dim command\n.");
> +	avail_coal->num_entries = cpu_to_le32(j);
> +	if (!virtnet_add_dim_command(vi, avail_coal))
> +		goto ret;
>
> -	for (i = 0; i < j; i++) {
> -		rq = &vi->rq[(coal->coal_vqs[i].vqn) / 2];
> -		rq->dim.state = DIM_START_MEASURE;
> -	}
> +	virtnet_cvq_response(vi, false);
> +	if (vi->cvq_cmd_nums)
> +		schedule_delayed_work(&vi->get_cvq, 1);
>
>  ret:
>  	rtnl_unlock();
> @@ -4402,7 +4523,9 @@ static int virtnet_find_vqs(struct virtnet_info *vi)
>
>  static int virtnet_alloc_queues(struct virtnet_info *vi)
>  {
> -	int i, len;
> +	struct virtnet_batch_coal *batch_coal;
> +	int i, position;
> +	u8 *buf;
>
>  	if (vi->has_cvq) {
>  		vi->ctrl = kzalloc(sizeof(*vi->ctrl), GFP_KERNEL);
> @@ -4418,13 +4541,21 @@ static int virtnet_alloc_queues(struct virtnet_info *vi)
>  	if (!vi->rq)
>  		goto err_rq;
>
> -	len = sizeof(struct virtnet_batch_coal) +
> -	      vi->max_queue_pairs * sizeof(struct virtio_net_ctrl_coal_vq);
> -	vi->batch_coal = kzalloc(len, GFP_KERNEL);
> -	if (!vi->batch_coal)
> +	buf = kzalloc(BATCH_CMD * (sizeof(struct virtnet_batch_coal) +
> +		      vi->max_queue_pairs * sizeof(struct virtnet_coal_entry)), GFP_KERNEL);
> +	if (!buf)
>  		goto err_coal;
>
> +	vi->batch_coal = (struct virtnet_batch_coal *)buf;
> +	for (i = 0; i < BATCH_CMD; i++) {
> +		position = i * (sizeof(struct virtnet_batch_coal) +
> +				vi->max_queue_pairs * sizeof(struct virtnet_coal_entry));
> +		batch_coal = (struct virtnet_batch_coal *)(&buf[position]);
> +		batch_coal->usable = true;
> +	}
> +
>  	INIT_DELAYED_WORK(&vi->refill, refill_work);
> +	INIT_DELAYED_WORK(&vi->get_cvq, get_cvq_work);
>  	for (i = 0; i < vi->max_queue_pairs; i++) {
>  		vi->rq[i].pages = NULL;
>  		netif_napi_add_weight(vi->dev, &vi->rq[i].napi, virtnet_poll,
> --
> 1.8.3.1
>
Xuan Zhuo Jan. 22, 2024, 7:42 a.m. UTC | #6 
On Tue, 16 Jan 2024 21:11:33 +0800, Heng Qi <hengqi@linux.alibaba.com> wrote:
> Accumulate multiple request commands to kick the device once,
> and obtain the processing results of the corresponding commands
> asynchronously. The batch command method is used to optimize the
> CPU overhead of the DIM worker caused by the guest being busy
> waiting for the command response result.
>
> On an 8-queue device, without this patch, the guest cpu overhead
> due to waiting for cvq could be 10+% and above. With this patch,
> the corresponding overhead is basically invisible.
>
> Signed-off-by: Heng Qi <hengqi@linux.alibaba.com>
> ---
>  drivers/net/virtio_net.c | 185 ++++++++++++++++++++++++++++++++++++++++-------
>  1 file changed, 158 insertions(+), 27 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index e4305ad..9f22c85 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -33,6 +33,8 @@
>  module_param(gso, bool, 0444);
>  module_param(napi_tx, bool, 0644);
>
> +#define BATCH_CMD 25
> +
>  /* FIXME: MTU in config. */
>  #define GOOD_PACKET_LEN (ETH_HLEN + VLAN_HLEN + ETH_DATA_LEN)
>  #define GOOD_COPY_LEN	128
> @@ -134,6 +136,9 @@ struct virtnet_interrupt_coalesce {
>  };
>
>  struct virtnet_batch_coal {
> +	struct virtio_net_ctrl_hdr hdr;
> +	virtio_net_ctrl_ack status;
> +	__u8 usable;
>  	__le32 num_entries;
>  	struct virtio_net_ctrl_coal_vq coal_vqs[];
>  };
> @@ -299,6 +304,7 @@ struct virtnet_info {
>
>  	/* Work struct for delayed refilling if we run low on memory. */
>  	struct delayed_work refill;
> +	struct delayed_work get_cvq;
>
>  	/* Is delayed refill enabled? */
>  	bool refill_enabled;
> @@ -326,6 +332,7 @@ struct virtnet_info {
>  	bool rx_dim_enabled;
>
>  	/* Interrupt coalescing settings */
> +	int cvq_cmd_nums;
>  	struct virtnet_batch_coal *batch_coal;
>  	struct virtnet_interrupt_coalesce intr_coal_tx;
>  	struct virtnet_interrupt_coalesce intr_coal_rx;
> @@ -2512,6 +2519,46 @@ static int virtnet_tx_resize(struct virtnet_info *vi,
>  	return err;
>  }
>
> +static bool virtnet_process_dim_cmd(struct virtnet_info *vi, void *res)
> +{
> +	struct virtnet_batch_coal *batch_coal;
> +	u16 queue;
> +	int i;
> +
> +	if (res != ((void *)vi)) {
> +		batch_coal = (struct virtnet_batch_coal *)res;
> +		batch_coal->usable = true;
> +		vi->cvq_cmd_nums--;
> +		for (i = 0; i < batch_coal->num_entries; i++) {
> +			queue = batch_coal->coal_vqs[i].vqn / 2;
> +			vi->rq[queue].dim.state = DIM_START_MEASURE;
> +		}
> +	} else {
> +		return true;
> +	}
> +
> +	return false;
> +}
> +
> +static bool virtnet_cvq_response(struct virtnet_info *vi, bool poll)
> +{
> +	unsigned tmp;
> +	void *res;
> +
> +	if (!poll) {
> +		while ((res = virtqueue_get_buf(vi->cvq, &tmp)) &&
> +		       !virtqueue_is_broken(vi->cvq))
> +			virtnet_process_dim_cmd(vi, res);
> +		return 0;
> +	}
> +
> +	while (!(res = virtqueue_get_buf(vi->cvq, &tmp)) &&
> +	       !virtqueue_is_broken(vi->cvq))
> +		cpu_relax();
> +
> +	return virtnet_process_dim_cmd(vi, res);
> +}
> +
>  /*
>   * Send command via the control virtqueue and check status.  Commands
>   * supported by the hypervisor, as indicated by feature bits, should
> @@ -2521,7 +2568,7 @@ static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
>  				 struct scatterlist *out)
>  {
>  	struct scatterlist *sgs[4], hdr, stat;
> -	unsigned out_num = 0, tmp;
> +	unsigned out_num = 0;
>  	int ret;
>
>  	/* Caller should know better */
> @@ -2555,9 +2602,9 @@ static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
>  	/* Spin for a response, the kick causes an ioport write, trapping
>  	 * into the hypervisor, so the request should be handled immediately.
>  	 */
> -	while (!virtqueue_get_buf(vi->cvq, &tmp) &&
> -	       !virtqueue_is_broken(vi->cvq))
> -		cpu_relax();
> +	while (true)
> +		if (virtnet_cvq_response(vi, true))
> +			break;
>
>  	return vi->ctrl->status == VIRTIO_NET_OK;
>  }
> @@ -2709,6 +2756,7 @@ static int virtnet_close(struct net_device *dev)
>  		cancel_work_sync(&vi->rq[i].dim.work);
>  	}
>
> +	cancel_delayed_work_sync(&vi->get_cvq);
>  	return 0;
>  }
>
> @@ -3520,22 +3568,99 @@ static int virtnet_send_notf_coal_vq_cmds(struct virtnet_info *vi,
>  	return 0;
>  }
>
> +static bool virtnet_add_dim_command(struct virtnet_info *vi,
> +				    struct virtnet_batch_coal *ctrl)
> +{
> +	struct scatterlist *sgs[4], hdr, stat, out;
> +	unsigned out_num = 0;
> +	int ret;
> +
> +	/* Caller should know better */
> +	BUG_ON(!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ));
> +
> +	ctrl->hdr.class = VIRTIO_NET_CTRL_NOTF_COAL;
> +	ctrl->hdr.cmd = VIRTIO_NET_CTRL_NOTF_COAL_VQS_SET;
> +
> +	/* Add header */
> +	sg_init_one(&hdr, &ctrl->hdr, sizeof(ctrl->hdr));
> +	sgs[out_num++] = &hdr;
> +
> +	/* Add body */
> +	sg_init_one(&out, &ctrl->num_entries, sizeof(ctrl->num_entries) +
> +		    ctrl->num_entries * sizeof(struct virtnet_coal_entry));
> +	sgs[out_num++] = &out;
> +
> +	/* Add return status. */
> +	ctrl->status = VIRTIO_NET_OK;
> +	sg_init_one(&stat, &ctrl->status, sizeof(ctrl->status));
> +	sgs[out_num] = &stat;
> +
> +	BUG_ON(out_num + 1 > ARRAY_SIZE(sgs));
> +	ret = virtqueue_add_sgs(vi->cvq, sgs, out_num, 1, ctrl, GFP_ATOMIC);
> +	if (ret < 0) {
> +		dev_warn(&vi->vdev->dev, "Failed to add sgs for command vq: %d\n.", ret);
> +		return false;
> +	}
> +
> +	virtqueue_kick(vi->cvq);
> +
> +	ctrl->usable = false;
> +	vi->cvq_cmd_nums++;
> +
> +	return true;
> +}


We should merge this to the function virtnet_send_command.


> +
> +static void get_cvq_work(struct work_struct *work)
> +{
> +	struct virtnet_info *vi =
> +		container_of(work, struct virtnet_info, get_cvq.work);
> +
> +	if (!rtnl_trylock()) {
> +		schedule_delayed_work(&vi->get_cvq, 5);
> +		return;
> +	}
> +
> +	if (!vi->cvq_cmd_nums)
> +		goto ret;
> +
> +	virtnet_cvq_response(vi, false);
> +
> +	if (vi->cvq_cmd_nums)
> +		schedule_delayed_work(&vi->get_cvq, 5);
> +
> +ret:
> +	rtnl_unlock();
> +}
> +
>  static void virtnet_rx_dim_work(struct work_struct *work)
>  {
>  	struct dim *dim = container_of(work, struct dim, work);
>  	struct receive_queue *rq = container_of(dim,
>  			struct receive_queue, dim);
>  	struct virtnet_info *vi = rq->vq->vdev->priv;
> +	struct virtnet_batch_coal *avail_coal;
>  	struct dim_cq_moder update_moder;
> -	struct virtnet_batch_coal *coal = vi->batch_coal;
> -	struct scatterlist sgs;
> -	int i, j = 0;
> +	int i, j = 0, position;
> +	u8 *buf;
>
>  	if (!rtnl_trylock()) {
>  		schedule_work(&dim->work);
>  		return;
>  	}
>
> +	if (vi->cvq_cmd_nums == BATCH_CMD || vi->cvq->num_free < 3 ||
> +	    vi->cvq->num_free <= (virtqueue_get_vring_size(vi->cvq) / 3))
> +		virtnet_cvq_response(vi, true);
> +
> +	for (i = 0; i < BATCH_CMD; i++) {
> +		buf = (u8 *)vi->batch_coal;
> +		position = i * (sizeof(struct virtnet_batch_coal) +
> +				vi->max_queue_pairs * sizeof(struct virtnet_coal_entry));
> +		avail_coal = (struct virtnet_batch_coal *)(&buf[position]);
> +		if (avail_coal->usable)
> +			break;


list or kmalloc here are all better way.


> +	}
> +
>  	/* Each rxq's work is queued by "net_dim()->schedule_work()"
>  	 * in response to NAPI traffic changes. Note that dim->profile_ix
>  	 * for each rxq is updated prior to the queuing action.
> @@ -3552,30 +3677,26 @@ static void virtnet_rx_dim_work(struct work_struct *work)
>  		update_moder = net_dim_get_rx_moderation(dim->mode, dim->profile_ix);
>  		if (update_moder.usec != rq->intr_coal.max_usecs ||
>  		    update_moder.pkts != rq->intr_coal.max_packets) {
> -			coal->coal_vqs[j].vqn = cpu_to_le16(rxq2vq(i));
> -			coal->coal_vqs[j].coal.max_usecs = cpu_to_le32(update_moder.usec);
> -			coal->coal_vqs[j].coal.max_packets = cpu_to_le32(update_moder.pkts);
> +			avail_coal->coal_vqs[j].vqn = cpu_to_le16(rxq2vq(i));
> +			avail_coal->coal_vqs[j].coal.max_usecs = cpu_to_le32(update_moder.usec);
> +			avail_coal->coal_vqs[j].coal.max_packets = cpu_to_le32(update_moder.pkts);
>  			rq->intr_coal.max_usecs = update_moder.usec;
>  			rq->intr_coal.max_packets = update_moder.pkts;
>  			j++;
> -		}
> +		} else if (dim->state == DIM_APPLY_NEW_PROFILE)
> +			dim->state = DIM_START_MEASURE;
>  	}
>
>  	if (!j)
>  		goto ret;
>
> -	coal->num_entries = cpu_to_le32(j);
> -	sg_init_one(&sgs, coal, sizeof(struct virtnet_batch_coal) +
> -		    j * sizeof(struct virtio_net_ctrl_coal_vq));
> -	if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_NOTF_COAL,
> -				  VIRTIO_NET_CTRL_NOTF_COAL_VQS_SET,
> -				  &sgs))
> -		dev_warn(&vi->vdev->dev, "Failed to add dim command\n.");
> +	avail_coal->num_entries = cpu_to_le32(j);
> +	if (!virtnet_add_dim_command(vi, avail_coal))
> +		goto ret;
>
> -	for (i = 0; i < j; i++) {
> -		rq = &vi->rq[(coal->coal_vqs[i].vqn) / 2];
> -		rq->dim.state = DIM_START_MEASURE;
> -	}
> +	virtnet_cvq_response(vi, false);

Is this usable?


> +	if (vi->cvq_cmd_nums)
> +		schedule_delayed_work(&vi->get_cvq, 1);
>
>  ret:
>  	rtnl_unlock();
> @@ -4402,7 +4523,9 @@ static int virtnet_find_vqs(struct virtnet_info *vi)
>
>  static int virtnet_alloc_queues(struct virtnet_info *vi)
>  {
> -	int i, len;
> +	struct virtnet_batch_coal *batch_coal;
> +	int i, position;
> +	u8 *buf;
>
>  	if (vi->has_cvq) {
>  		vi->ctrl = kzalloc(sizeof(*vi->ctrl), GFP_KERNEL);
> @@ -4418,13 +4541,21 @@ static int virtnet_alloc_queues(struct virtnet_info *vi)
>  	if (!vi->rq)
>  		goto err_rq;
>
> -	len = sizeof(struct virtnet_batch_coal) +
> -	      vi->max_queue_pairs * sizeof(struct virtio_net_ctrl_coal_vq);
> -	vi->batch_coal = kzalloc(len, GFP_KERNEL);
> -	if (!vi->batch_coal)
> +	buf = kzalloc(BATCH_CMD * (sizeof(struct virtnet_batch_coal) +
> +		      vi->max_queue_pairs * sizeof(struct virtnet_coal_entry)), GFP_KERNEL);
> +	if (!buf)
>  		goto err_coal;
>
> +	vi->batch_coal = (struct virtnet_batch_coal *)buf;
> +	for (i = 0; i < BATCH_CMD; i++) {
> +		position = i * (sizeof(struct virtnet_batch_coal) +
> +				vi->max_queue_pairs * sizeof(struct virtnet_coal_entry));
> +		batch_coal = (struct virtnet_batch_coal *)(&buf[position]);
> +		batch_coal->usable = true;
> +	}
> +
>  	INIT_DELAYED_WORK(&vi->refill, refill_work);
> +	INIT_DELAYED_WORK(&vi->get_cvq, get_cvq_work);
>  	for (i = 0; i < vi->max_queue_pairs; i++) {
>  		vi->rq[i].pages = NULL;
>  		netif_napi_add_weight(vi->dev, &vi->rq[i].napi, virtnet_poll,
> --
> 1.8.3.1
>
diff mbox series

Patch

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index e4305ad..9f22c85 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -33,6 +33,8 @@ 
 module_param(gso, bool, 0444);
 module_param(napi_tx, bool, 0644);
 
+#define BATCH_CMD 25
+
 /* FIXME: MTU in config. */
 #define GOOD_PACKET_LEN (ETH_HLEN + VLAN_HLEN + ETH_DATA_LEN)
 #define GOOD_COPY_LEN	128
@@ -134,6 +136,9 @@  struct virtnet_interrupt_coalesce {
 };
 
 struct virtnet_batch_coal {
+	struct virtio_net_ctrl_hdr hdr;
+	virtio_net_ctrl_ack status;
+	__u8 usable;
 	__le32 num_entries;
 	struct virtio_net_ctrl_coal_vq coal_vqs[];
 };
@@ -299,6 +304,7 @@  struct virtnet_info {
 
 	/* Work struct for delayed refilling if we run low on memory. */
 	struct delayed_work refill;
+	struct delayed_work get_cvq;
 
 	/* Is delayed refill enabled? */
 	bool refill_enabled;
@@ -326,6 +332,7 @@  struct virtnet_info {
 	bool rx_dim_enabled;
 
 	/* Interrupt coalescing settings */
+	int cvq_cmd_nums;
 	struct virtnet_batch_coal *batch_coal;
 	struct virtnet_interrupt_coalesce intr_coal_tx;
 	struct virtnet_interrupt_coalesce intr_coal_rx;
@@ -2512,6 +2519,46 @@  static int virtnet_tx_resize(struct virtnet_info *vi,
 	return err;
 }
 
+static bool virtnet_process_dim_cmd(struct virtnet_info *vi, void *res)
+{
+	struct virtnet_batch_coal *batch_coal;
+	u16 queue;
+	int i;
+
+	if (res != ((void *)vi)) {
+		batch_coal = (struct virtnet_batch_coal *)res;
+		batch_coal->usable = true;
+		vi->cvq_cmd_nums--;
+		for (i = 0; i < batch_coal->num_entries; i++) {
+			queue = batch_coal->coal_vqs[i].vqn / 2;
+			vi->rq[queue].dim.state = DIM_START_MEASURE;
+		}
+	} else {
+		return true;
+	}
+
+	return false;
+}
+
+static bool virtnet_cvq_response(struct virtnet_info *vi, bool poll)
+{
+	unsigned tmp;
+	void *res;
+
+	if (!poll) {
+		while ((res = virtqueue_get_buf(vi->cvq, &tmp)) &&
+		       !virtqueue_is_broken(vi->cvq))
+			virtnet_process_dim_cmd(vi, res);
+		return 0;
+	}
+
+	while (!(res = virtqueue_get_buf(vi->cvq, &tmp)) &&
+	       !virtqueue_is_broken(vi->cvq))
+		cpu_relax();
+
+	return virtnet_process_dim_cmd(vi, res);
+}
+
 /*
  * Send command via the control virtqueue and check status.  Commands
  * supported by the hypervisor, as indicated by feature bits, should
@@ -2521,7 +2568,7 @@  static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
 				 struct scatterlist *out)
 {
 	struct scatterlist *sgs[4], hdr, stat;
-	unsigned out_num = 0, tmp;
+	unsigned out_num = 0;
 	int ret;
 
 	/* Caller should know better */
@@ -2555,9 +2602,9 @@  static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
 	/* Spin for a response, the kick causes an ioport write, trapping
 	 * into the hypervisor, so the request should be handled immediately.
 	 */
-	while (!virtqueue_get_buf(vi->cvq, &tmp) &&
-	       !virtqueue_is_broken(vi->cvq))
-		cpu_relax();
+	while (true)
+		if (virtnet_cvq_response(vi, true))
+			break;
 
 	return vi->ctrl->status == VIRTIO_NET_OK;
 }
@@ -2709,6 +2756,7 @@  static int virtnet_close(struct net_device *dev)
 		cancel_work_sync(&vi->rq[i].dim.work);
 	}
 
+	cancel_delayed_work_sync(&vi->get_cvq);
 	return 0;
 }
 
@@ -3520,22 +3568,99 @@  static int virtnet_send_notf_coal_vq_cmds(struct virtnet_info *vi,
 	return 0;
 }
 
+static bool virtnet_add_dim_command(struct virtnet_info *vi,
+				    struct virtnet_batch_coal *ctrl)
+{
+	struct scatterlist *sgs[4], hdr, stat, out;
+	unsigned out_num = 0;
+	int ret;
+
+	/* Caller should know better */
+	BUG_ON(!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ));
+
+	ctrl->hdr.class = VIRTIO_NET_CTRL_NOTF_COAL;
+	ctrl->hdr.cmd = VIRTIO_NET_CTRL_NOTF_COAL_VQS_SET;
+
+	/* Add header */
+	sg_init_one(&hdr, &ctrl->hdr, sizeof(ctrl->hdr));
+	sgs[out_num++] = &hdr;
+
+	/* Add body */
+	sg_init_one(&out, &ctrl->num_entries, sizeof(ctrl->num_entries) +
+		    ctrl->num_entries * sizeof(struct virtnet_coal_entry));
+	sgs[out_num++] = &out;
+
+	/* Add return status. */
+	ctrl->status = VIRTIO_NET_OK;
+	sg_init_one(&stat, &ctrl->status, sizeof(ctrl->status));
+	sgs[out_num] = &stat;
+
+	BUG_ON(out_num + 1 > ARRAY_SIZE(sgs));
+	ret = virtqueue_add_sgs(vi->cvq, sgs, out_num, 1, ctrl, GFP_ATOMIC);
+	if (ret < 0) {
+		dev_warn(&vi->vdev->dev, "Failed to add sgs for command vq: %d\n.", ret);
+		return false;
+	}
+
+	virtqueue_kick(vi->cvq);
+
+	ctrl->usable = false;
+	vi->cvq_cmd_nums++;
+
+	return true;
+}
+
+static void get_cvq_work(struct work_struct *work)
+{
+	struct virtnet_info *vi =
+		container_of(work, struct virtnet_info, get_cvq.work);
+
+	if (!rtnl_trylock()) {
+		schedule_delayed_work(&vi->get_cvq, 5);
+		return;
+	}
+
+	if (!vi->cvq_cmd_nums)
+		goto ret;
+
+	virtnet_cvq_response(vi, false);
+
+	if (vi->cvq_cmd_nums)
+		schedule_delayed_work(&vi->get_cvq, 5);
+
+ret:
+	rtnl_unlock();
+}
+
 static void virtnet_rx_dim_work(struct work_struct *work)
 {
 	struct dim *dim = container_of(work, struct dim, work);
 	struct receive_queue *rq = container_of(dim,
 			struct receive_queue, dim);
 	struct virtnet_info *vi = rq->vq->vdev->priv;
+	struct virtnet_batch_coal *avail_coal;
 	struct dim_cq_moder update_moder;
-	struct virtnet_batch_coal *coal = vi->batch_coal;
-	struct scatterlist sgs;
-	int i, j = 0;
+	int i, j = 0, position;
+	u8 *buf;
 
 	if (!rtnl_trylock()) {
 		schedule_work(&dim->work);
 		return;
 	}
 
+	if (vi->cvq_cmd_nums == BATCH_CMD || vi->cvq->num_free < 3 ||
+	    vi->cvq->num_free <= (virtqueue_get_vring_size(vi->cvq) / 3))
+		virtnet_cvq_response(vi, true);
+
+	for (i = 0; i < BATCH_CMD; i++) {
+		buf = (u8 *)vi->batch_coal;
+		position = i * (sizeof(struct virtnet_batch_coal) +
+				vi->max_queue_pairs * sizeof(struct virtnet_coal_entry));
+		avail_coal = (struct virtnet_batch_coal *)(&buf[position]);
+		if (avail_coal->usable)
+			break;
+	}
+
 	/* Each rxq's work is queued by "net_dim()->schedule_work()"
 	 * in response to NAPI traffic changes. Note that dim->profile_ix
 	 * for each rxq is updated prior to the queuing action.
@@ -3552,30 +3677,26 @@  static void virtnet_rx_dim_work(struct work_struct *work)
 		update_moder = net_dim_get_rx_moderation(dim->mode, dim->profile_ix);
 		if (update_moder.usec != rq->intr_coal.max_usecs ||
 		    update_moder.pkts != rq->intr_coal.max_packets) {
-			coal->coal_vqs[j].vqn = cpu_to_le16(rxq2vq(i));
-			coal->coal_vqs[j].coal.max_usecs = cpu_to_le32(update_moder.usec);
-			coal->coal_vqs[j].coal.max_packets = cpu_to_le32(update_moder.pkts);
+			avail_coal->coal_vqs[j].vqn = cpu_to_le16(rxq2vq(i));
+			avail_coal->coal_vqs[j].coal.max_usecs = cpu_to_le32(update_moder.usec);
+			avail_coal->coal_vqs[j].coal.max_packets = cpu_to_le32(update_moder.pkts);
 			rq->intr_coal.max_usecs = update_moder.usec;
 			rq->intr_coal.max_packets = update_moder.pkts;
 			j++;
-		}
+		} else if (dim->state == DIM_APPLY_NEW_PROFILE)
+			dim->state = DIM_START_MEASURE;
 	}
 
 	if (!j)
 		goto ret;
 
-	coal->num_entries = cpu_to_le32(j);
-	sg_init_one(&sgs, coal, sizeof(struct virtnet_batch_coal) +
-		    j * sizeof(struct virtio_net_ctrl_coal_vq));
-	if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_NOTF_COAL,
-				  VIRTIO_NET_CTRL_NOTF_COAL_VQS_SET,
-				  &sgs))
-		dev_warn(&vi->vdev->dev, "Failed to add dim command\n.");
+	avail_coal->num_entries = cpu_to_le32(j);
+	if (!virtnet_add_dim_command(vi, avail_coal))
+		goto ret;
 
-	for (i = 0; i < j; i++) {
-		rq = &vi->rq[(coal->coal_vqs[i].vqn) / 2];
-		rq->dim.state = DIM_START_MEASURE;
-	}
+	virtnet_cvq_response(vi, false);
+	if (vi->cvq_cmd_nums)
+		schedule_delayed_work(&vi->get_cvq, 1);
 
 ret:
 	rtnl_unlock();
@@ -4402,7 +4523,9 @@  static int virtnet_find_vqs(struct virtnet_info *vi)
 
 static int virtnet_alloc_queues(struct virtnet_info *vi)
 {
-	int i, len;
+	struct virtnet_batch_coal *batch_coal;
+	int i, position;
+	u8 *buf;
 
 	if (vi->has_cvq) {
 		vi->ctrl = kzalloc(sizeof(*vi->ctrl), GFP_KERNEL);
@@ -4418,13 +4541,21 @@  static int virtnet_alloc_queues(struct virtnet_info *vi)
 	if (!vi->rq)
 		goto err_rq;
 
-	len = sizeof(struct virtnet_batch_coal) +
-	      vi->max_queue_pairs * sizeof(struct virtio_net_ctrl_coal_vq);
-	vi->batch_coal = kzalloc(len, GFP_KERNEL);
-	if (!vi->batch_coal)
+	buf = kzalloc(BATCH_CMD * (sizeof(struct virtnet_batch_coal) +
+		      vi->max_queue_pairs * sizeof(struct virtnet_coal_entry)), GFP_KERNEL);
+	if (!buf)
 		goto err_coal;
 
+	vi->batch_coal = (struct virtnet_batch_coal *)buf;
+	for (i = 0; i < BATCH_CMD; i++) {
+		position = i * (sizeof(struct virtnet_batch_coal) +
+				vi->max_queue_pairs * sizeof(struct virtnet_coal_entry));
+		batch_coal = (struct virtnet_batch_coal *)(&buf[position]);
+		batch_coal->usable = true;
+	}
+
 	INIT_DELAYED_WORK(&vi->refill, refill_work);
+	INIT_DELAYED_WORK(&vi->get_cvq, get_cvq_work);
 	for (i = 0; i < vi->max_queue_pairs; i++) {
 		vi->rq[i].pages = NULL;
 		netif_napi_add_weight(vi->dev, &vi->rq[i].napi, virtnet_poll,