RE: [PATCH v4] net: netvsc: Update default VMBus channels

[Michael Kelley]

From: Erni Sri Satya Vennela <ernis@xxxxxxxxxxxxxxxxxxx> Sent: Monday, August 26, 2024 10:17 PM
> 
> Change VMBus channels macro (VRSS_CHANNEL_DEFAULT) in
> Linux netvsc from 8 to 16 to align with Azure Windows VM
> and improve networking throughput.
> 
> For VMs having less than 16 vCPUS, the channels depend
> on number of vCPUs. For greater than 16 vCPUs,
> set the channels to maximum of VRSS_CHANNEL_DEFAULT and
> number of physical cores / 2 which is returned by
> netif_get_num_default_rss_queues() as a way to optimize CPU
> resource utilization and scale for high-end processors with
> many cores.
> Maximum number of channels are by default set to 64.
> 
> Based on this change the channel creation would change as follows:
> 
> -----------------------------------------------------------------
> | No. of vCPU |  dev_info->num_chn |    channels created        |
> -----------------------------------------------------------------
> |    1-16     |        16	   |          vCPU              |
> |    >16      |  max(16,#cores/2)  | min(64 , max(16,#cores/2)) |
> -----------------------------------------------------------------
> 
> Performance tests showed significant improvement in throughput:
> - 0.54% for 16 vCPUs
> - 0.83% for 32 vCPUs
> - 0.86% for 48 vCPUs
> - 9.72% for 64 vCPUs
> - 13.57% for 96 vCPUs
> 
> Signed-off-by: Erni Sri Satya Vennela <ernis@xxxxxxxxxxxxxxxxxxx>
> Reviewed-by: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
> Reviewed-by: Shradha Gupta <shradhagupta@xxxxxxxxxxxxxxxxxxx>
> ---
> Changes in v4:
> * Update commit message for channels created
> ---
> Changes in v3:
> * Use netif_get_num_default_rss_queues() to set channels
> * Change terminology for channels in commit message
> ---
> Changes in v2:
> * Set dev_info->num_chn based on vCPU count.
> ---
>  drivers/net/hyperv/hyperv_net.h | 2 +-
>  drivers/net/hyperv/netvsc_drv.c | 3 ++-
>  2 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/hyperv/hyperv_net.h b/drivers/net/hyperv/hyperv_net.h
> index 810977952f95..e690b95b1bbb 100644
> --- a/drivers/net/hyperv/hyperv_net.h
> +++ b/drivers/net/hyperv/hyperv_net.h
> @@ -882,7 +882,7 @@ struct nvsp_message {
> 
>  #define VRSS_SEND_TAB_SIZE 16  /* must be power of 2 */
>  #define VRSS_CHANNEL_MAX 64
> -#define VRSS_CHANNEL_DEFAULT 8
> +#define VRSS_CHANNEL_DEFAULT 16
> 
>  #define RNDIS_MAX_PKT_DEFAULT 8
>  #define RNDIS_PKT_ALIGN_DEFAULT 8
> diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
> index 44142245343d..a6482afe4217 100644
> --- a/drivers/net/hyperv/netvsc_drv.c
> +++ b/drivers/net/hyperv/netvsc_drv.c
> @@ -987,7 +987,8 @@ struct netvsc_device_info *netvsc_devinfo_get(struct
> netvsc_device *nvdev)
>  			dev_info->bprog = prog;
>  		}
>  	} else {
> -		dev_info->num_chn = VRSS_CHANNEL_DEFAULT;
> +		dev_info->num_chn = max(VRSS_CHANNEL_DEFAULT,
> +					netif_get_num_default_rss_queues());
>  		dev_info->send_sections = NETVSC_DEFAULT_TX;
>  		dev_info->send_section_size = NETVSC_SEND_SECTION_SIZE;
>  		dev_info->recv_sections = NETVSC_DEFAULT_RX;
> --
> 2.34.1
> 

Reviewed-by: Michael Kelley <mhklinux@xxxxxxxxxxx>