linux-kernel - Re: [RFC PATCH]vhost-blk: In-kernel accelerator for virtio block device

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Date:	Wed, 10 Aug 2011 10:19:49 +0800
From:	Liu Yuan <namei.unix@...il.com>
To:	Badari Pulavarty <pbadari@...ibm.com>
CC:	Stefan Hajnoczi <stefanha@...il.com>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Avi Kivity <avi@...hat.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, Khoa Huynh <khoa@...ibm.com>
Subject: Re: [RFC PATCH]vhost-blk: In-kernel accelerator for virtio block
 device

On 08/09/2011 01:16 AM, Badari Pulavarty wrote:
> On 8/8/2011 12:31 AM, Liu Yuan wrote:
>> On 08/08/2011 01:04 PM, Badari Pulavarty wrote:
>>> On 8/7/2011 6:35 PM, Liu Yuan wrote:
>>>> On 08/06/2011 02:02 AM, Badari Pulavarty wrote:
>>>>> On 8/5/2011 4:04 AM, Liu Yuan wrote:
>>>>>> On 08/05/2011 05:58 AM, Badari Pulavarty wrote:
>>>>>>> Hi Liu Yuan,
>>>>>>>
>>>>>>> I started testing your patches. I applied your kernel patch to 3.0
>>>>>>> and applied QEMU to latest git.
>>>>>>>
>>>>>>> I passed 6 blockdevices from the host to guest (4 vcpu, 4GB RAM).
>>>>>>> I ran simple "dd" read tests from the guest on all block devices
>>>>>>> (with various blocksizes, iflag=direct).
>>>>>>>
>>>>>>> Unfortunately, system doesn't stay up. I immediately get into
>>>>>>> panic on the host. I didn't get time to debug the problem. 
>>>>>>> Wondering
>>>>>>> if you have seen this issue before and/or you have new patchset
>>>>>>> to try ?
>>>>>>>
>>>>>>> Let me know.
>>>>>>>
>>>>>>> Thanks,
>>>>>>> Badari
>>>>>>>
>>>>>>
>>>>>> Okay, it is actually a bug pointed out by MST on the other 
>>>>>> thread, that it needs a mutex for completion thread.
>>>>>>
>>>>>> Now would you please this attachment?This patch only applies to 
>>>>>> kernel part, on top of v1 kernel patch.
>>>>>>
>>>>>> This patch mainly moves completion thread into vhost thread as a 
>>>>>> function. As a result, both requests submitting and completion 
>>>>>> signalling is in the same thread.
>>>>>>
>>>>>> Yuan
>>>>>
>>>>> Unfortunately, "dd" tests (4 out of 6) in the guest hung. I see 
>>>>> following messages
>>>>>
>>>>> virtio_blk virtio2: requests: id 0 is not a head !
>>>>> virtio_blk virtio3: requests: id 1 is not a head !
>>>>> virtio_blk virtio5: requests: id 1 is not a head !
>>>>> virtio_blk virtio1: requests: id 1 is not a head !
>>>>>
>>>>> I still see host panics. I will collect the host panic and see if 
>>>>> its still same or not.
>>>>>
>>>>> Thanks,
>>>>> Badari
>>>>>
>>>>>
>>>> Would you please show me how to reproduce it step by step? I tried 
>>>> dd with two block device attached, but didn't get hung nor panic.
>>>>
>>>> Yuan
>>>
>>> I did 6 "dd"s on 6 block devices..
>>>
>>> dd if=/dev/vdb of=/dev/null bs=1M iflag=direct &
>>> dd if=/dev/vdc of=/dev/null bs=1M iflag=direct &
>>> dd if=/dev/vdd of=/dev/null bs=1M iflag=direct &
>>> dd if=/dev/vde of=/dev/null bs=1M iflag=direct &
>>> dd if=/dev/vdf of=/dev/null bs=1M iflag=direct &
>>> dd if=/dev/vdg of=/dev/null bs=1M iflag=direct &
>>>
>>> I can reproduce the problem with in 3 minutes :(
>>>
>>> Thanks,
>>> Badari
>>>
>>>
>> Ah...I made an embarrassing mistake that I tried to 'free()' an 
>> kmem_cache object.
>>
>> Would you please revert the vblk-for-kernel-2 patch and apply the new 
>> one attached in this letter?
>>
> Hmm.. My version of the code seems to have kzalloc() for used_info. I 
> don't have a version
> that is using kmem_cache_alloc(). Would it be possible for you to send 
> out complete patch
> (with all the fixes applied) for me to try ? This will avoid all the 
> confusion ..
>
> Thanks,
> Badari
>
>
Okay, please apply the attached patch to the vanilla kernel. :)

Thanks,
Yuan

View attachment "vhost-blk-for-kernel.patch" of type "text/x-patch" (20764 bytes)