[ovs-dev] [PATCH v2 1/1] DPDK: Remove support for vhost-user zero-copy.

Ilya Maximets i.maximets at ovn.org
Tue Sep 29 16:44:27 UTC 2020


On 9/29/20 6:33 PM, Stokes, Ian wrote:
>> On 9/10/20 7:30 PM, Ian Stokes wrote:
>>> Support for vhost-user dequeue zero-copy was deprecated in OVS 2.14
>> with
>>> the aim of removing it for OVS 2.15.
>>>
>>> OVS only supports zero copy for vhost client mode, as such it will cease
>>> to function due to DPDK commit [1]
>>>
>>> Also DPDK is set to remove zero-copy functionality in DPDK 20.11 as
>>> referenced by commit [2]
>>>
>>> As such remove support from OVS.
>>>
>>> [1] 715070ea10e6 ("vhost: prevent zero-copy with incompatible client
>> mode")
>>> [2] d21003c9dafa ("doc: announce removal of vhost zero-copy dequeue")
>>>
>>> Signed-off-by: Ian Stokes <ian.stokes at intel.com>
>>>
>>> ---
>>> v1 -> v2
>>> * Remove reference to zero copy in vhost post copy documentation.
>>> * Add DPDK commits that have influenced OVS decision to remove support
>>>   for zero-copy.
>>> * Correct NEWS to reference removal rather than deprecation of zc.
>>> ---
>>>  Documentation/topics/dpdk/vhost-user.rst | 76 --------------------------------
>>>  NEWS                                     |  2 +
>>>  lib/netdev-dpdk.c                        | 25 -----------
>>>  vswitchd/vswitch.xml                     | 11 -----
>>>  4 files changed, 2 insertions(+), 112 deletions(-)
>>>
>>> diff --git a/Documentation/topics/dpdk/vhost-user.rst
>> b/Documentation/topics/dpdk/vhost-user.rst
>>> index 4af738d11..3be8f8b5e 100644
>>> --- a/Documentation/topics/dpdk/vhost-user.rst
>>> +++ b/Documentation/topics/dpdk/vhost-user.rst
>>> @@ -339,10 +339,6 @@ The default value is ``false``.
>>>      migration recovery was fixed for post-copy in 3.0 and few additional bug
>>>      fixes (like userfaulfd leak) was released in 3.0.1.
>>>
>>> -    DPDK Post-copy feature requires avoiding to populate the guest
>> memory
>>> -    (application must not call mlock* syscall). So enabling mlockall and
>>> -    dequeue zero-copy features is mis-compatible with post-copy feature.
>>
>> The part about mlockall is still valid, only zero-copy related words should be
>> removed, e.g. "So enabling mlockall is mis-compatible with post-copy
>> feature."
> 
> Apologies for the delay Ilya, I was on PTO the last few weeks, sure will make think change and apply with an ACK from yourself if that’s ok?

OK, sure.  With this change:
Acked-by: Ilya Maximets <i.maximets at ovn.org>

> 
> Regards
> Ian
>>
>> Best regards, Ilya Maximets.



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