Subject: Re: [Xen-devel] [PATCH 1/2] xen-netback: limit xen vif max queues number to online cpus

From: Joe Jin <[email-masked]>
Date: Fri, 23 Oct 2015 16:33:15 +0800

Hi Jan,

Thanks for you review, will create new patches with your comments.

Regards,
Joe
On 10/23/2015 04:20 PM, Jan Beulich wrote:
>>>> On 23.10.15 at 09:58, <[email-masked]> wrote:
>> --- a/drivers/net/xen-netback/netback.c
>> +++ b/drivers/net/xen-netback/netback.c
>> @@ -68,7 +68,9 @@ unsigned int rx_stall_timeout_msecs = 60000;
>>  module_param(rx_stall_timeout_msecs, uint, 0444);
>>  
>>  unsigned int xenvif_max_queues;
>> -module_param_named(max_queues, xenvif_max_queues, uint, 0644);
>> +static int xennet_set_max_queues(const char *val, struct kernel_param *kp);
>> +module_param_call(max_queues, xennet_set_max_queues, param_get_int,
> 
> param_get_uint
> 
>> +		  &xenvif_max_queues, 0600);
> 
> Why the change from mode 0644 to 0600?
> 
>> @@ -107,6 +109,20 @@ static struct xen_netif_rx_response *make_rx_response(struct xenvif_queue *queue
>>  					     u16      size,
>>  					     u16      flags);
>>  
>> +static int xennet_set_max_queues(const char *val, struct kernel_param *kp)
>> +{
>> +	unsigned int cpus = num_online_cpus();
>> +	unsigned int max_queues = simple_strtoul(val, NULL, 10);
>> +
>> +	if (max_queues == 0 || max_queues > cpus) {
>> +		pr_info("max_queues %d is out of range [0 - %d]!\n", 
> 
> %u in both cases.
> 
>> +			max_queues, cpus);
>> +		return -EINVAL;
> 
> Considering the message: -ERANGE?
> 
>> +	}
>> +
>> +	return param_set_int(val, kp);
> 
> param_set_uint()
> 
>> @@ -2110,15 +2126,15 @@ int xenvif_dealloc_kthread(void *data)
>>  static int __init netback_init(void)
>>  {
>>  	int rc = 0;
>> +	unsigned int cpus = num_online_cpus();
>>  
>>  	if (!xen_domain())
>>  		return -ENODEV;
>>  
>> -	/* 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();
>> +	/* Allow at most as many queues as CPUs. */
>> +	if (xenvif_max_queues == 0 || xenvif_max_queues > cpus)
>> +		xenvif_max_queues = cpus;
>> +	pr_info("vif max_queues: %d\n", xenvif_max_queues);
> 
> %u again.
> 
> Jan
> 

-- 
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