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Subject: Re: [PATCH v3 6/9] xen/blkfront: negotiate the number of hw
 queues/rings with backend
To: Bob Liu <bob.liu@oracle.com>
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From: =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= <roger.pau@citrix.com>
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Date: Wed, 7 Oct 2015 13:46:13 +0200
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El 07/10/15 a les 12.39, Bob Liu ha escrit:
> On 10/05/2015 10:40 PM, Roger Pau Monné wrote:
>> El 05/09/15 a les 14.39, Bob Liu ha escrit:
>>> @@ -2267,6 +2335,12 @@ static int __init xlblk_init(void)
>>>  		xen_blkif_max_ring_order = 0;
>>>  	}
>>>  
>>> +	if (xen_blkif_max_queues > nr_cpus) {
>>
>> Shouldn't there be a default value for xen_blkif_max_queues if the user
>> hasn't set the parameter on the command line?
>>
> 
> Then the default value is 0, multi-queue isn't enabled by default.

Why isn't it enabled by default with a sensible number of queues? I
guess something like:

if (xen_blkif_max_queues == 0)
	xen_blkif_max_queues = min(nr_cpus, 4);

Roger.