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

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Date:	Mon, 08 Aug 2011 15:31:47 +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 08/08/2011 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?

Yuan,
Thanks

View attachment "vblk-for-kernel-2.patch" of type "text/x-patch" (3279 bytes)