Re: [dpdk-dev] Beyond DPDK 2.0

[Avi Kivity <avi@cloudius-systems.com>]

On 05/07/2015 06:49 PM, Wiles, Keith wrote:
>
> On 5/7/15, 8:33 AM, "Avi Kivity" <avi@cloudius-systems.com> wrote:
>
>> On 05/07/2015 06:27 PM, Wiles, Keith wrote:
>>> On 5/7/15, 7:02 AM, "Avi Kivity" <avi@cloudius-systems.com> wrote:
>>>
>>>> On Wed, Apr 22, 2015 at 6:11 PM, O'Driscoll, Tim
>>>> <tim.o'driscoll@intel.com>
>>>> wrote:
>>>>
>>>>> Does anybody have any input or comments on this?
>>>>>
>>>>>
>>>>>> -----Original Message-----
>>>>>> From: O'Driscoll, Tim
>>>>>> Sent: Thursday, April 16, 2015 11:39 AM
>>>>>> To: dev@dpdk.org
>>>>>> Subject: Beyond DPDK 2.0
>>>>>>
>>>>>> Following the launch of DPDK by Intel as an internal development
>>>>>> project, the launch of dpdk.org by 6WIND in 2013, and the first DPDK
>>>>> RPM
>>>>>> packages for Fedora in 2014, 6WIND, Red Hat and Intel would like to
>>>>>> prepare for future releases after DPDK 2.0 by starting a discussion
>>>>>> on
>>>>>> its evolution. Anyone is welcome to join this initiative.
>>>>>>
>>>>>> Since then, the project has grown significantly:
>>>>>> -    The number of commits and mailing list posts has increased
>>>>>> steadily.
>>>>>> -    Support has been added for a wide range of new NICs (Mellanox
>>>>>> support submitted by 6WIND, Cisco VIC, Intel i40e and fm10k etc.).
>>>>>> -    DPDK is now supported on multiple architectures (IBM Power
>>>>> support
>>>>>> in DPDK 1.8, Tile support submitted by EZchip but not yet reviewed or
>>>>>> applied).
>>>>>>
>>>>>> While this is great progress, we need to make sure that the project
>>>>>> is
>>>>>> structured in a way that enables it to continue to grow. To achieve
>>>>>> this, 6WIND, Red Hat and Intel would like to start a discussion about
>>>>>> the future of the project, so that we can agree and establish
>>>>> processes
>>>>>> that satisfy the needs of the current and future DPDK community.
>>>>>>
>>>>>> We're very interested in hearing the views of everybody in the
>>>>>> community. In addition to debate on the mailing list, we'll also
>>>>>> schedule community calls to discuss this.
>>>>>>
>>>>>>
>>>>>> Project Goals
>>>>>> -------------
>>>>>>
>>>>>> Some topics to be considered for the DPDK project include:
>>>>>> -    Project Charter: The charter of the DPDK project should be
>>>>> clearly
>>>>>> defined, and should explain the limits of DPDK (what it does and does
>>>>>> not cover). This does not mean that we would be stuck with a singular
>>>>>> charter for all time, but the direction and intent of the project
>>>>> should
>>>>>> be well understood.
>>>> One problem we've seen with dpdk is that it is a framework, not a
>>>> library:
>>>> it wants to create threads, manage memory, and generally take over.
>>>> This
>>>> is a problem for us, as we are writing a framework (seastar, [1]) and
>>>> need
>>>> to create threads, manage memory, and generally take over ourselves.
>>>>
>>>> Perhaps dpdk can be split into two layers, a library layer that only
>>>> provides mechanisms, and a framework layer that glues together those
>>>> mechanisms and applies a policy, trading in generality for ease of use.
>>> The DPDK system is somewhat divided now between the EAL, PMDS and
>>> utility
>>> functions like malloc/rings/Š
>>>
>>> The problem I see is the PMDs need a framework to be usable and the EAL
>>> plus the ethdev layers provide that support today. Setting up and
>>> initializing the DPDK system is pretty clean just call the EAL init
>>> routines along with the pool creates and the basic configs for the
>>> PMDs/hardware. Once the system is inited one can create new threads and
>>> not requiring anyone to use DPDK launch routines. Maybe I am not
>>> understanding your needs can you explain more?
>> An initialization routine that accepts argc/argv can hardly be called
>> clean.
> You want a config file or structure initialization design? If that is the
> case you can contribute that support as another way to initialize DPDK.

A config file would be even worse.  But we are discussing why 
dpdk-as-a-framework is detrimental, not new ways for me to contribute.

>> In seastar, we have our own malloc() (since seastar is sharded we can
>> provide a faster thread-unsafe malloc implementation).  We also have our
>> own threading, and since dpdk is an optional component in seastar, dpdk
>> support requires code duplication.
> DPDK replies one the huge page support for allocation to get the
> performance, do you also not require huge page support.

Sorry, is this a question?  Please rephrase.

>   The malloc system
> in DPDK can be used as a replacement for the standard malloc if that works
> for your needs. Also after DPDK inits you can use your own malloc and any
> other tools you want to use.

How is memory partitioned between dpdk and my application?  If I 
underallocate dpdk memory, something bad will happen.  If I overallocate 
dpdk memory, then I am depriving my application of this memory.  A 
common pool means I do not overallocate or underallocate, but since dpdk 
insists on managing its own pools, I can't do this.

>   I do not see a lot of duplicate code here
> IMO. I guess if you are installing into a very small memory system then
> yes it could be a problem, but DPDK is was not designed to run in a system
> with limited memory.

I am not talking about duplicate code, but about duplicate 
functionality, done slightly differently.  I want to use dpdk in the 
same way as I use every other library, by calling its initialization 
routine and then calling its functions.  In this scenario, the library 
is passive, only reacting to my calls.  The way dpdk works now is 
actively, taking over resources, creating thread, and calling my code 
instead of the other way round.

>
>> I would like to launch my own threads, pin them where I like, and call
>> PMD drivers to send and receive packets.  Practically everything else
>> that dpdk does gets in my way, including mbuf pools.  I'd much prefer to
>> allocate mbufs myself.
> You do not need to use the lauching of threads in the EAL and can supply
> your own, right?

Right.

> Regards,
> ++Keith
>>
>>>> [1] http://seastar-project.org