[dpdk-dev] Why nothing since 1.8.0?

[O'driscoll, Tim]

> -----Original Message-----
> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Neil Horman
> Sent: Thursday, January 15, 2015 6:51 PM
> To: Thomas Monjalon
> Cc: dev at dpdk.org
> Subject: Re: [dpdk-dev] Why nothing since 1.8.0?
> 
> On Thu, Jan 15, 2015 at 06:25:33PM +0100, Thomas Monjalon wrote:
> > 2015-01-15 08:06, Neil Horman:
> > > On Thu, Jan 15, 2015 at 10:51:38AM +0100, Thomas Monjalon wrote:
> > > > 2015-01-15 04:27, Ouyang, Changchun:
> > > > > From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Zhang, Helin
> > > > > > From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Neil
> Horman
> > > > > > > On Wed, Jan 14, 2015 at 12:23:52PM -0800, Stephen Hemminger
> wrote:
> > > > > > > > Ok, so 1.8.0 came out almost a month ago and none of the
> patches
> > > > > > > > that were deferred waiting for the release got merged since
> then.
> > > > > > > > Last commit in git is the 1.8.0 release.
> > > > > > > >
> > > > > > > > Where is the post-merge window bundle, where are the later
> commits?
> > > > > > > > Lots of patches are sitting rotting in patchwork...
> > > > > > >
> > > > > > > +1, I've had the same questions.
> > > > > > > Neil
> > > > > >
> > > > > > +1, Some patch set might be ready for being merged.
> > > > >
> > > > > +1,  the earlier some patches are merged into mainline, and the easier
> those
> > > > > sequent patch sets can resolve their conflicts.
> > > >
> > > > +1, there are some patches which are properly reviewed
> > > >
> > > > Reminder: sub-tree to manage specific part of DPDK can be open on
> request
> > >
> > > Ok, I think what you're saying here is you're too busy to handle all the
> patches
> > > comming in at the moment.  As such I'd like to propose a sub-tree
> encompassing
> > > all the pmds in DPDK.  I would envision that including all the acutal pmd's
> in
> > > the tree, as well as the infrastructure that is used to interface them to the
> > > core (i.e. the ethdev/rte_ether library).  I'll gladly maintain the patch pool
> > > and send you pull requests.
> >
> > The list of PMDs is increasing:
> > 	librte_pmd_af_packet
> > 	librte_pmd_bond
> > 	librte_pmd_e1000
> > 	librte_pmd_enic
> > 	librte_pmd_i40e
> > 	librte_pmd_ixgbe
> > 	librte_pmd_pcap
> > 	librte_pmd_ring
> > 	librte_pmd_virtio
> > 	librte_pmd_vmxnet3
> > 	librte_pmd_xenvirt
> > There is already some sub-trees for bnx2x, fm10k and i40e:
> > 	http://dpdk.org/browse/
> >
> Yes, and I've mentioned before that that is an absolutely silly way to break
> out
> subtrees.  You have to find a balance of workload distribution and developer
> convienience.
> 
> I also note that these are problematic because you're not merging anything
> from them. Is it your intention to keep bnx2 and fm10k separate in
> perpituity?
> If so, thats a real problem, because then we effectively just have several out
> of tree drivers, and thats just unacceptible.
> 
> > > If you could set me up with a login to dpdk.org, I'd appreciate it.
> >
> > It is preferred to have 1 sub-tree per module.
> > What do you think of managing contributions for af_packet and/or virtio?
> > It would make sense as virtio is a RedHat technology.
> > Maybe it could include vhost lib and example.
> >
> No, for reasons I've mentioned before.  If you take each pmd/library and
> create
> a subtree for it, you've created the most fine grained control of subtrees you
> could ask for, but you've created a nighmare of a burden on developers who
> want
> to update any code, especially if they have patches that hit multiple trees.
> 
> Look at some of the stats in the dpdk tree:
> 
> Library		Commits between 1.7.0 and 1.8.0
> librte_acl		5
> librte_cfgfile		0
> librte_cmdline		4
> librte_compat		0
> librte_distributor 	5
> librte_eal 		125
> librte_ether 		31
> librte_hash 		1
> librte_ip_frag 		5
> librte_ivshmem 		0
> librte_kni 		2
> librte_kvargs 		0
> librte_lpm 		1
> librte_malloc 		1
> librte_mbuf 		39
> librte_mempool 		4
> librte_meter 		0
> librte_net 		4
> librte_pipeline 	0
> librte_pmd_af_packet 	4
> librte_pmd_bond 	20
> librte_pmd_e1000 	21
> librte_pmd_enic 	12
> librte_pmd_i40e 	90
> librte_pmd_ixgbe 	83
> librte_pmd_pcap 	4
> librte_pmd_ring 	0
> librte_pmd_virtio 	21
> librte_pmd_vmxnet3 	21
> librte_pmd_xenvirt 	6
> librte_port 		6
> librte_power 		3
> librte_ring 		2
> librte_sched 		1
> librte_table 		7
> librte_timer 		0
> librte_vhost 		30
> 
> If you look at all of the pmds in the dpdk tree, we're talking about ~300
> patches per release.  If you look at the net-next tree for the linux kernel,
> Dave Miller merged 569 patches on his own (based on the following
> command:
> git log --pretty=format:%H v3.17..v3.18 -- drivers/net/ethernet/ net/core/ |
> wc
> -l)
> 
> And that doesn't account for the ~500 patches that come in via pull request
> from
> the wireless subtree.  Nor does it account for the merge window for net-
> next
> being 2 months instead of dpdk's 6 months.  Theres no need in any way for
> 12
> maintainers to be twiddling their thumbs waiting on ~20 patches each, and
> for
> that split, you've forced developers to potentially develop patches against 12
> trees (12 being the current number of PMD's that are in the dpdk).
> 
> The right answer here is balance.  Let me split out the pmd's and ethernet
> infrastructure libraries to a subtree.  I'll pull in patches posted regarding
> pmd's and librte_ether/ip_frag etc, and send you a pull requests after each
> release so you get all the latest bits, and then pulls for stabilization on each
> -rc. I can manage 300 patches without issue, and that takes a load off your
> shoulders.  I'll get fm10k integrated, as well as bnx2.  That gives us a single
> alternate tree for developers to go to for pmd and pmd infrastructure
> updates.
> Its a win-win.
> 
> Regards
> Neil

I agree with Thomas on this. The approach we've been taking for PMDs for newer Intel NICs is to have a separate sub-repository with a maintainer who's an expert in the area. This offloads some work from Thomas, ensures that the maintainer is very familiar with the PMD code and the corresponding hardware, and doesn't involve too much additional work for the developers involved (as you said, there isn't a huge volume of commits for any individual PMD). We have this in place for i40e now, and will be applying this to fm10k, which hasn't been upstreamed yet but will be in time for the 2.0 release. Based on our experiences with those, we may well look at extending the model to include PMDs for other Intel NICs, and possibly other libraries, as well.

As you said, there's a balance to be struck, and too many subtrees may become unmanageable. With respect to your concern about developers having to potentially develop patches against multiple subtrees, this has never been raised as a concern by any of our development team. Is there any historical data on the number of changes that would fall into this category so we can see if it's a real problem or not?


Tim