Re: [PATCH v3 6/9] xen/blkfront: negotiate the number of hw queues/rings with backend

From	Bob Liu <bob.liu@oracle.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v3 6/9] xen/blkfront: negotiate the number of hw queues/rings with backend
Date	2015-10-07 14:30 +0200
Message-ID	<qgW15-4HJ-39@gated-at.bofh.it> (permalink)
References	<q5l4R-J8-3@gated-at.bofh.it> <q5l4S-J8-9@gated-at.bofh.it> <qgffs-1Q6-11@gated-at.bofh.it> <qgUsi-2md-13@gated-at.bofh.it> <qgVom-3Hn-3@gated-at.bofh.it>
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On 10/07/2015 07:46 PM, Roger Pau Monné wrote:
> 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);
> 

I'm worry about complains about more memory consumption if set to 4 by default.
Anyway, if you think it's fine I'll update the default value to 4 in next version.

-- 
Regards,
-Bob
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Re: [PATCH v3 6/9] xen/blkfront: negotiate the number of hw queues/rings  with backend Bob Liu <bob.liu@oracle.com> - 2015-10-07 12:50 +0200
  Re: [PATCH v3 6/9] xen/blkfront: negotiate the number of hw  queues/rings with backend Roger Pau Monné <roger.pau@citrix.com> - 2015-10-07 13:50 +0200
    Re: [PATCH v3 6/9] xen/blkfront: negotiate the number of hw queues/rings  with backend Bob Liu <bob.liu@oracle.com> - 2015-10-07 14:30 +0200

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