Libguestfs - Aug 2020 - Re: [PATCH nbdkit] vddk: Relax threading model and enable multi-conn.

On 8/5/20 7:48 AM, Richard W.M. Jones wrote:
> See comment in code and
> https://www.redhat.com/archives/libguestfs/2020-August/msg00023.html
> ---
>   plugins/vddk/vddk.c | 32 ++++++++++++++++++++++++++++----
>   1 file changed, 28 insertions(+), 4 deletions(-)
I'll have to trust your testing, but code-wise, this looks safe.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

On Wed, Aug 05, 2020 at 08:12:26AM -0500, Eric Blake
wrote:
> On 8/5/20 7:48 AM, Richard W.M. Jones wrote:
> >See comment in code and
> >https://www.redhat.com/archives/libguestfs/2020-August/msg00023.html
> >---
> >  plugins/vddk/vddk.c | 32 ++++++++++++++++++++++++++++----
> >  1 file changed, 28 insertions(+), 4 deletions(-)
> 
> I'll have to trust your testing, but code-wise, this looks safe.
I'm in a bit two minds about this one.  It appears safe.  OTOH it's
somewhat risky in theory, and it doesn't give us very much performance
improvement.

Let's discuss alternate implementations with Nir in the other thread.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
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On 8/5/20 8:32 AM, Richard W.M. Jones wrote:
> On Wed, Aug 05, 2020 at 08:12:26AM -0500, Eric Blake wrote:
>> On 8/5/20 7:48 AM, Richard W.M. Jones wrote:
>>> See comment in code and
>>>
https://www.redhat.com/archives/libguestfs/2020-August/msg00023.html
>>> ---
>>>   plugins/vddk/vddk.c | 32 ++++++++++++++++++++++++++++----
>>>   1 file changed, 28 insertions(+), 4 deletions(-)
>>
>> I'll have to trust your testing, but code-wise, this looks safe.
> 
> I'm in a bit two minds about this one.  It appears safe.  OTOH it's
> somewhat risky in theory, and it doesn't give us very much performance
> improvement.
I agree that we are NOT strictly following the VDDK documentation, in 
that this risks 2 different threads calling VDiskLib_Open (even though 
we have serialized it so that only one open is ever active at a time). 
So it is indeed risky.
> 
> Let's discuss alternate implementations with Nir in the other thread.
I'll respond there.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org