linux-kernel - Re: [PATCH v5 00/10] xen-block: multi hardware-queues/rings support

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Date:	Thu, 26 Nov 2015 11:20:33 -0500
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Bob Liu <bob.liu@...cle.com>
CC:	xen-devel@...ts.xen.org, linux-kernel@...r.kernel.org,
	roger.pau@...rix.com, felipe.franciosi@...rix.com, axboe@...com,
	avanzini.arianna@...il.com, rafal.mielniczuk@...rix.com,
	jonathan.davies@...rix.com, david.vrabel@...rix.com
Subject: Re: [PATCH v5 00/10] xen-block: multi hardware-queues/rings support

On November 26, 2015 2:09:02 AM EST, Bob Liu <bob.liu@...cle.com> wrote:
>
>On 11/26/2015 10:57 AM, Konrad Rzeszutek Wilk wrote:
>> On Thu, Nov 26, 2015 at 10:28:10AM +0800, Bob Liu wrote:
>>>
>>> On 11/26/2015 06:12 AM, Konrad Rzeszutek Wilk wrote:
>>>> On Wed, Nov 25, 2015 at 03:56:03PM -0500, Konrad Rzeszutek Wilk
>wrote:
>>>>> On Wed, Nov 25, 2015 at 02:25:07PM -0500, Konrad Rzeszutek Wilk
>wrote:
>>>>>>>   xen/blkback: separate ring information out of struct xen_blkif
>>>>>>>   xen/blkback: pseudo support for multi hardware queues/rings
>>>>>>>   xen/blkback: get the number of hardware queues/rings from
>blkfront
>>>>>>>   xen/blkback: make pool of persistent grants and free pages
>per-queue
>>>>>>
>>>>>> OK, got to those as well. I have put them in 'devel/for-jens-4.5'
>and
>>>>>> are going to test them overnight before pushing them out.
>>>>>>
>>>>>> I see two bugs in the code that we MUST deal with:
>>>>>>
>>>>>>  - print_stats () is going to show zero values.
>>>>>>  - the sysfs code (VBD_SHOW) aren't converted over to fetch data
>>>>>>    from all the rings.
>>>>>
>>>>> - kthread_run can't handle the two "name, i" arguments. I see:
>>>>>
>>>>> root      5101     2  0 20:47 ?        00:00:00 [blkback.3.xvda-]
>>>>> root      5102     2  0 20:47 ?        00:00:00 [blkback.3.xvda-]
>>>>
>>>> And doing save/restore:
>>>>
>>>> xl save <id> /tmp/A;
>>>> xl restore /tmp/A;
>>>>
>>>> ends up us loosing the proper state and not getting the ring setup
>back.
>>>> I see this is backend:
>>>>
>>>> [ 2719.448600] vbd vbd-22-51712: -1 guest requested 0 queues,
>exceeding the maximum of 3.
>>>>
>>>> And XenStore agrees:
>>>> tool = ""
>>>>  xenstored = ""
>>>> local = ""
>>>>  domain = ""
>>>>   0 = ""
>>>>    domid = "0"
>>>>    name = "Domain-0"
>>>>    device-model = ""
>>>>     0 = ""
>>>>      state = "running"
>>>>    error = ""
>>>>     backend = ""
>>>>      vbd = ""
>>>>       2 = ""
>>>>        51712 = ""
>>>>         error = "-1 guest requested 0 queues, exceeding the maximum
>of 3."
>>>>
>>>> .. which also leads to a memory leak as xen_blkbk_remove never gets
>>>> called.
>>>
>>> I think which was already fix by your patch:
>>> [PATCH RFC 2/2] xen/blkback: Free resources if connect_ring failed.
>> 
>> Nope. I get that with or without the patch.
>> 
>
>Attached patch should fix this issue. 

Yup!

Thanks!


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