On 02/08/2018 12:19 PM, Ilya Maximets wrote:
>> Hi all,
>>
>> As discussed on the OVS-DPDK community call, I've manually reverted the per 
>> port mempool changes in OVS-DPDK on a branch on my own git hub. This had to 
>> be re-introduced manually due to the number of commits and work that had 
>> went on top of the per port implementation.
>>
>> For testing people can access it from the link below:
>>
>> https://github.com/istokes/ovs/tree/mempool_revert
>>
>> If we are to revert this in time for OVS 2.9 there is a need for validation 
>> among the community to ensure that it does not break any features. I have 
>> validated most existing features with VSperf but I'm more interested in 
>> ensuring existing user test cases do not break with this revert.
> 
> I thought that we wanted to update the documentation for now with new
> memory requirements, prepare new mempool model for 2.10 and backport it
> to 2.9 if necessary., As mentioned here:
> 
>       
> https://mail.openvswitch.org/pipermail/ovs-discuss/2018-January/046101.html
> 
> I'm sorry, but I see no meeting minutes for the latest OVS-DPDK sync call.
> 

As per other mail - just haven't had time to send yet. Will send shortly.

> In general, I think that temporary reverting of the current model looks not
> so pretty. Especially if we're going to almost revert this revertion in the
> future.
> 

I think it's a pretty clean revert. I've reviewed it and tested out
things like MTU reconfig, sharing, not sharing mempools etc.

It is not clear that a few fixes on branch-2.9 will make the per port
mempool ok to use. It seems strange that OVS 2.9 would go out with
backwards compatibility broken but with a promise it will try to be
fixed in the future on the branch with *new* memory model development.
AFAIK, there is no proposal for what the new memory model would look like.

> Does you RFC patch intended for branch-2.9 only? In this case it may be
> acceptable. We'll continue working on current model for 2.10 to fix all
> the issues or implement some completely new model. And branch-2.9 will be
> left with shared mempool model forever. Did I understand correctly?
> 

Good point about possible difference in branch-2.9 vs. master. I was
thinking about branch-2.9 only wrt revert. If there is a thought that
mempool per port can be fixed or could be useful as part of a user
choice etc., then maybe it would make sense to not revert on master,
subject to more development of a better solution.

> Best regards, Ilya Maximets.
> 

It's not perfect, but we've replaced something that has been working
with little or no complaints for 4 years with something that breaks
backwards compatibility for some users, and some (like Jan) possibly
can't even use OVS at all like this. I think it makes sense to revert it
for OVS 2.9 and rethink how to make memory scale - maybe that will be
per port memory pools with fixes, maybe some hybrid scheme, maybe some
sort of user intervention to choose scheme or memory sizes.

thanks,
Kevin.

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