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

From: Badari Pulavarty <pbadari@us.ibm.com>
To: Liu Yuan <namei.unix@gmail.com>
Cc: Stefan Hajnoczi <stefanha@gmail.com>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	Rusty Russell <rusty@rustcorp.com.au>,
	Avi Kivity <avi@redhat.com>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	Khoa Huynh <khoa@us.ibm.com>
Subject: Re: [RFC PATCH]vhost-blk: In-kernel accelerator for virtio block device
Date: Sun, 07 Aug 2011 22:04:50 -0700	[thread overview]
Message-ID: <4E3F6E72.1000907@us.ibm.com> (raw)
In-Reply-To: <4E3F3D4E.70104@gmail.com>

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