Re: [dpdk-dev] 19.11.4 patches review and test

[Thomas Monjalon <thomas@monjalon.net>]

22/03/2021 15:27, Christian Ehrhardt:
> On Mon, Mar 22, 2021 at 1:25 PM Thomas Monjalon <thomas@monjalon.net> wrote:
> > 22/03/2021 12:59, Luca Boccassi:
> > > On Mon, 2021-03-22 at 11:41 +0000, Bruce Richardson wrote:
> > > > On Mon, Mar 22, 2021 at 10:49:54AM +0100, Christian Ehrhardt wrote:
> > > > > On Thu, Mar 18, 2021 at 7:25 PM Pai G, Sunil <sunil.pai.g@intel.com> wrote:
> > > > > > Hi Christian, Ilya
> > > > > > From: Ilya Maximets <i.maximets@ovn.org>
> > > > > > > On 3/18/21 2:36 PM, Pai G, Sunil wrote:
> > > > > > > > Hey Christian,
> > > > > > > >
> > > > > > > > <snipped>
> > > > > > > >
> > > > > > > > > back  in 19.11.4 these DPDK changes were not picked up as they have
> > > > > > > > > broken builds as discussed here.
> > > > > > > > > Later on the communication was that all this works fine now and
> > > > > > > > > thereby Luca has "reverted the reverts" in 19.11.6 [1].
> > > > > > > > >
> > > > > > > > > But today we were made aware that still no OVS 2.13 builds against a
> > > > > > > > > DPDK that has those changes.
> > > > > > > > > Not 2.13.1 as we have it in Ubuntu nor (if it needs some OVS changes
> > > > > > > > > backported) the recent 2.13.3 does build.
> > > > > > > > > They still fail with the very same issue I reported [2] back then.
> > > > > > > > >
> > > > > > > > > Unfortunately I have just released 19.11.7 so I can't revert them
> > > > > > > > > there - but OTOH reverting and counter reverting every other release
> > > > > > > > > seems wrong anyway.
> > > > > > >
> > > > > > > It is wrong indeed, but the main question here is why these patches was
> > > > > > > backported to stable release in a first place?
> > > > > > >
> > > > > > > Looking at these patches, they are not actual bug fixes but more like "nice to
> > > > > > > have" features that additionally breaks the way application links with DPDK.
> > > > > > > Stuff like that should not be acceptable to the stable release without a strong
> > > > > > > justification or, at least, testing with actual applications.
> > > > >
> > > > > I agree, but TBH IIRC these changes were initially by OVS people :-)
> > > > > One could chase down the old talks between Luca and the requesters, but I don't
> > > > > think that gains us that much.
> > > > >
> > > > > > > Since we already have a revert of revert, revert of revert of revert doesn't
> > > > > > > seem so bad.
> > > > >
> > > > > As long as we don't extend this series, yeah
> > > > >
> > > > > > > > > I wanted to ask if there is a set of patches that OVS would need to
> > > > > > > > > backport to 2.13.x to make this work?
> > > > > > > > > If they could be identified and prepared Distros could use them on
> > > > > > > > > 2.13.3 asap and 2.13.4 could officially release them for OVS later on.
> > > > > > > > >
> > > > > > > > > But for that we'd need a hint which OVS changes that would need to be.
> > > > > > > > > All I know atm is from the testing reports on DPDK it seems that OVS
> > > > > > > > > 2.14.3 and 2.15 are happy with the new DPDK code.
> > > > > > > > > Do you have pointers on what 2.13.3 would need to get backported to
> > > > > > > > > work again in regard to this build issue.
> > > > > > > >
> > > > > > > > You would need to use partial contents from patch :
> > > > > > > > http://patchwork.ozlabs.org/project/openvswitch/patch/1608142365-
> > > > > > > 26215
> > > > > > > > -1-git-send-email-ian.stokes@intel.com/
> > > > > > > >
> > > > > > > > If you'd like me to send patches which would work with 2.13, 2.14, I'm
> > > > > > > > ok with that too.[keeping only those parts from patch which fixes the issue
> > > > > > > you see.] But we must ensure it doesn’t cause problems for OVS too.
> > > > > > > > Your thoughts Ilya ?
> > > > > > >
> > > > > > > We had more fixes on top of this particular patch and I'd like to not cherry-
> > > > > > > pick and re-check all of this again.
> > > > > >
> > > > > > I agree, we had more fixes on top of this. It would be risky to cherry-pick.
> > > > > > So it might be a better option to revert.
> > > > >
> > > > > I agree, as far as I assessed the situation it would mean the revert
> > > > > of the following list.
> > > > > And since that is a lot of "reverts" in the string, to be clear it means that
> > > > > those original changes would not be present anymore in 19.11.x.
> > > > >
> > > > > f49248a990 Revert "Revert "build/pkg-config: prevent overlinking""
> > > > > 39586a4cf0 Revert "Revert "build/pkg-config: improve static linking flags""
> > > > > 906e935a1f Revert "Revert "build/pkg-config: output drivers first for
> > > > > static build""
> > > > > deebf95239 Revert "Revert "build/pkg-config: move pkg-config file creation""
> > > > > a3bd9a34bf Revert "Revert "build: always link whole DPDK static libraries""
> > > > > d4bc124438 Revert "Revert "devtools: test static linkage with pkg-config""
> > > > >
> > > > > But to avoid going back&forth I'd prefer to have a signed-off on that
> > > > > approach from:
> > > > > - Luca (for 19.11.6 which has added the changes)
> > > > > - Bruce (for being involved in the old&new case in general)
> > > > > - Thomas (for general master maintainer thoughts)
> > > > >
> > > >
> > > > If this is what is needed to ensure OVS can continue to use this release
> > > > series, then I am absolutely fine with it.
> > >
> > > This was requested by OVS, so if they don't need it anymore it's fine
> > > by me as well
> >
> > I am not sure to understand the full story,
> > but I am a bit worried that our release is dictated by
> > a single "user" (project using DPDK).
> 
> Sure, fair to ask for more detail :-)
> 
> > Please do you have links of discussion history?
> 
> I ordered the events by time and added links to those occasions that I
> could find:
> 
> July 2020            - Initial request by OVS - *1
> July 2020            - Initial queuing     -
> http://mails.dpdk.org/archives/stable/2020-July/024248.html
> September 2020 - Issues identified; changes reverted    -
> http://mails.dpdk.org/archives/stable/2020-September/024796.html
> October 2020      - Re-applying early in 19.11.6 cycle    - *1
> November 2020  - Tests didn't spot it with 19.11.6 as OVS 2.14.x (not
> the 2.13 LTS) was tested    -
> https://doc.dpdk.org/guides-19.11/rel_notes/release_19_11.html#id16
> March 2021         - Same issue re-found in >=19.11.6    -
> http://mails.dpdk.org/archives/stable/2021-March/029418.html
> 
> *1 - Luca and I looked for logs, there are no links that I'd know of
> and Luca said it might have come up as a request during a meeting.

First, I agree to revert the changes again if it causes a regression.
Second, do we know the root cause of the issue?
Is it a problem with the version of pkg-config?
Is it OK with DPDK 20.11?

About the process, I see multiple issues:

1/ Some patches were backported for OVS only,
but it could break other applications.

2/ It is not clear whether the patches were really needed in 19.11.

3/ There is no trace of backport requests in the mailing list.

So I feel we should be stricter on the reasons for a backport.
Note: I am not blaming anyone. Everybody tries to do the best.
I believe sharing requests and discussions on the mailing list
could help in the decision process.

Thanks for all the work.