Re: [Xen-devel] [PATCH net] xen-netback: respect user provided max_queues

[David Vrabel <david.vrabel@xxxxxxxxxx>]

On 09/09/15 11:09, Wei Liu wrote:
> Originally that parameter was always reset to num_online_cpus during
> module initialisation, which renders it useless.
> 
> The fix is to only set max_queues to num_online_cpus when user has not
> provided a value.
[...]
> --- a/drivers/net/xen-netback/netback.c
> +++ b/drivers/net/xen-netback/netback.c
> @@ -67,7 +67,7 @@ module_param(rx_drain_timeout_msecs, uint, 0444);
>  unsigned int rx_stall_timeout_msecs = 60000;
>  module_param(rx_stall_timeout_msecs, uint, 0444);
>  
> -unsigned int xenvif_max_queues;
> +unsigned int xenvif_max_queues = 0;

You don't need this.

Otherwise,

Reviewed-by: David Vrabel <david.vrabel@xxxxxxxxxx>

Is an equivalent fix needed in netfront?

David

>  module_param_named(max_queues, xenvif_max_queues, uint, 0644);
>  MODULE_PARM_DESC(max_queues,
>                "Maximum number of queues per virtual interface");
> @@ -2105,8 +2105,11 @@ static int __init netback_init(void)
>       if (!xen_domain())
>               return -ENODEV;
>  
> -     /* Allow as many queues as there are CPUs, by default */
> -     xenvif_max_queues = num_online_cpus();
> +     /* Allow as many queues as there are CPUs if user has not
> +      * specified a value.
> +      */
> +     if (xenvif_max_queues == 0)
> +             xenvif_max_queues = num_online_cpus();
>  
>       if (fatal_skb_slots < XEN_NETBK_LEGACY_SLOTS_MAX) {
>               pr_info("fatal_skb_slots too small (%d), bump it to 
> XEN_NETBK_LEGACY_SLOTS_MAX (%d)\n",
> 


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