Re: [PATCH v6 2/2] eal: add asynchronous request API to DPDK IPC

From: "Burakov, Anatoly" <anatoly.burakov@intel.com>
To: Thomas Monjalon <thomas@monjalon.net>
Cc: "Tan, Jianfeng" <jianfeng.tan@intel.com>,
	"Van Haaren, Harry" <harry.van.haaren@intel.com>,
	dev@dpdk.org, "Ananyev,
	Konstantin" <konstantin.ananyev@intel.com>,
	bruce.richardson@intel.com, olivier.matz@6wind.com
Subject: Re: [PATCH v6 2/2] eal: add asynchronous request API to DPDK IPC
Date: Wed, 28 Mar 2018 13:21:30 +0100	[thread overview]
Message-ID: <92df6ce3-6657-76ac-c07b-8a0798f06106@intel.com> (raw)
In-Reply-To: <2138949.TA61XZhXVp@xps>

On 28-Mar-18 12:26 PM, Thomas Monjalon wrote:
> 28/03/2018 12:42, Burakov, Anatoly:
>> On 28-Mar-18 10:53 AM, Thomas Monjalon wrote:
>>> 28/03/2018 11:21, Burakov, Anatoly:
>> I'm not against trying to improve the core design. I'm just saying that,
>> had this kind of feedback been provided just a bit earlier, I would've
>> had time to fix it in time for deadlines. However, because memory rework
>> patchset depends on this API, i would suggest merging it in now, as is,
>> and commit to a roadmap of improvements for next release(s).
> 
> Actually, you had the feedback yourself from the beginning.
> You decided to gave up with interrupt thread because its implementation
> is not complete (and maybe far from perfect).

That's not quite how i see it, but OK, suppose so.

> There are some communities where it is not acceptable to workaround
> core issues because of timing issues. I think we accept it in DPDK,
> but I continue to question it, in order to be sure that everybody is OK
> with this kind of tradeoff.

The way i see it, not all API's are equal; some are more important than 
others. This is a new, experimental API that is not core to any DPDK 
function - it's not used on any hotpaths nor is it even that demanding 
(the two threads will be sleeping 99.999% of the time anyway). I think 
we're allowed to experiment on it before settling on an implementation 
that satisfies everyone :)

>> For starters, we could plan on removing alarm thread's dependency on
>> rte_malloc and just use regular malloc API's in there, and rework
>> asynchronous IPC API to use that instead. This shouldn't be much work,
>> and will presumably make you halfway happy, as one of the threads will
>> be gone :)
>>
>> We can then look into removing the second thread and moving the entirety
>> of DPDK IPC into the interrupt thread. I'm not too sure how would that
>> work, but i haven't looked at it in any detail, so maybe it is feasible.
>>
>> Can we agree on this? It would be great to do everything perfectly from
>> the first try, but having a goal in sight and working towards it is fine
>> too, even if not all of the steps we take are perfect.
> 
> The main concern is API.
> If all these changes are internal only, and does not involve any major
> API change, then I guess it is OK to pospone them in next release.
> 

Yes, all of this is/will be internal to DPDK IPC - no externally visible 
changes whatsoever.

-- 
Thanks,
Anatoly