From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vlad Yasevich Subject: Re: [PATCH net-next v2] bridge: vlan: allow to suppress local mac install for all vlans Date: Fri, 28 Aug 2015 21:11:56 -0400 Message-ID: <55E106DC.5040802@redhat.com> References: <1440549295-3979-1-git-send-email-razor@blackwall.org> <20150825.194222.390859854071446877.davem@davemloft.net> <20150825.230641.773630246486190390.davem@davemloft.net> <55DE98AF.8000503@cumulusnetworks.com> <2125A434-6529-4D5A-BA6B-9F64C6B7A8C0@cumulusnetworks.com> <55DFA1A3.30601@redhat.com> <691CF770-DDF3-4AC9-B99C-9640992037C5@cumulusnetworks.com> <55E05486.5090500@redhat.com> Reply-To: vyasevic@redhat.com Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Cc: bridge@lists.linux-foundation.org, netdev@vger.kernel.org, roopa , wkok@cumulusnetworks.com, David Miller To: Nikolay Aleksandrov Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: bridge-bounces@lists.linux-foundation.org Errors-To: bridge-bounces@lists.linux-foundation.org List-Id: netdev.vger.kernel.org On 08/28/2015 11:26 AM, Nikolay Aleksandrov wrote: >=20 >> On Aug 28, 2015, at 5:31 AM, Vlad Yasevich wrote= : >> >> On 08/27/2015 10:17 PM, Nikolay Aleksandrov wrote: >>> >>>> On Aug 27, 2015, at 4:47 PM, Vlad Yasevich wro= te: >>>> >>>> On 08/27/2015 05:02 PM, Nikolay Aleksandrov wrote: >>>>> >>>>>> On Aug 26, 2015, at 9:57 PM, roopa wro= te: >>>>>> >>>>>> On 8/26/15, 4:33 AM, Nikolay Aleksandrov wrote: >>>>>>>> On Aug 25, 2015, at 11:06 PM, David Miller = wrote: >>>>>>>> >>>>>>>> From: Nikolay Aleksandrov >>>>>>>> Date: Tue, 25 Aug 2015 22:28:16 -0700 >>>>>>>> >>>>>>>>> Certainly, that should be done and I will look into it, but the >>>>>>>>> essence of this patch is a bit different. The problem here is n= ot >>>>>>>>> the size of the fdb entries, it=E2=80=99s more the number of th= em - having >>>>>>>>> 96000 entries (even if they were 1 byte ones) is just way too m= uch >>>>>>>>> especially when the fdb hash size is small and static. We could= work >>>>>>>>> on making it dynamic though, but still these type of local entr= ies >>>>>>>>> per vlan per port can easily be avoided with this option. >>>>>>>> 96000 bits can be stored in 12k. Get where I'm going with this? >>>>>>>> >>>>>>>> Look at the problem sideways. >>>>>>> Oh okay, I misunderstood your previous comment. I=E2=80=99ll look= into that. >>>>>>> >>>>>> I just wanted to add the other problems we have had with keeping t= hese macs (mostly from userspace POV): >>>>>> - add/del netlink notification storms >>>>>> - and large netlink dumps >>>>>> >>>>>> In addition to in-kernel optimizations, will be nice to have a sol= ution that reduces the burden on userspace. That will need a newer netlin= k dump format for fdbs. Considering all the changes needed, Nikolays patc= h seems less intrusive. >>>>> >>>>> Right, we need to take these into account as well. I=E2=80=99ll con= tinue the discussion on this (or restart it) because >>>>> I looked into using a bitmap for the local entries only and while i= t fixes the scalability issue, it presents >>>>> a few new ones which are mostly related to the fact that these entr= ies now exist only without a vlan >>>>> and if a new mac comes along which matches one of these but is in a= vlan, the entry will get created >>>>> in br_fdb_update() unless we add a second lookup, but that will slo= w down the learning path. >>>>> Also this change requires an update of every fdb function that uses= the vid as a key (every fdb function?!) >>>>> because now we can have the mac in two places instead of one which = is a pretty big churn with lots >>>>> of conditionals all over the place and I don=E2=80=99t like it. Add= ing this complexity for the local addresses only >>>>> seems like an overkill, so I think to drop this issue for now. >>>> >>>> I seem to recall Roopa and I and maybe a few others have discussing = this a few >>>> years ago at plumbers, I can't remember the details any more. All t= hese local >>>> addresses add a ton of confusion. Does anyone (Stephen?) remember w= hat the >>>> original reason was for all these local addresses? I wonder if we ca= n have >>>> a nob to disable all of them (not just per vlan)? That might be cle= aner and >>>> easier to swallow. >>>> >>> >>> Right, this would be the easiest way and if the others agree - I=E2=80= =99ll post a patch for it so we can >>> have some way to resolve it today and even if we fix the scalability = issue, this is still a valid case >>> that some people don=E2=80=99t want local fdbs installed automaticall= y. >>> Any objections to this ? >>> >>>>> This patch (that works around the initial problem) also has these i= ssues. >>>>> Note that one way to take care of this in a more straight-forward w= ay would be to have each entry >>>>> with some sort of a bitmap (like Vlad has tried earlier) and then w= e can combine the paths so most >>>>> of these issues disappear, but that will not be easy as was already= commented earlier. I=E2=80=99ve looked >>>>> briefly into doing this with rhashtable so we can keep the memory f= ootprint for each entry relatively >>>>> small but it still affects the performance and we can have thousand= s of resizes happening.=20 >>>>> >>>> >>>> So, one of the earlier approaches that I've tried (before rhashtable= was >>>> in the kernel) was to have a hash of vlan ids each with a data struc= ture >>>> pointing to a list of ports for a given vlan as well as a list of fd= bs for >>>> a given vlan. As far as scalability goes, that's really the best ap= proach. >>>> It would also allow us to do packet accounting per vlan. The only c= oncern >>>> at the time was performance of ingress lookup. I think rhashtables= might >>>> help with this as well as ability to grow the footprint of the vlan = hash >>>> table dynamically. >>>> >>>> -vlad >>>> >>> I=E2=80=99ll look into it but I=E2=80=99m guessing the learning will = become a more complicated process with additional=20 >>> allocations and some hash handling. >> >> I don't remember learning being all that complicated. The hash only c= hanged under >> rtnl when vlans were added/removed. The nice this is that we wouldn't= need >> to rebalance, because if the vlan is removed all fdb links get removed= too. They >> don't move to another bucket (But that was with static hash. Need to = look at rhash in >> more detail). >> >> If you want, I might still have patches hanging around on my machine t= hat had a hash >> table implementation. I can send them to you. >> >> -vlad >> >=20 > :-) Okay, I=E2=80=99m putting the crystal ball away. If you could send = me these patches it=E2=80=99d be great so > I don=E2=80=99t have to start this from scratch. >=20 So, I forgot that I lost an old disk that had all that code, so I am a bi= t bummed about that. I did however find the series that got posted. http://www.spinics.net/lists/netdev/msg219737.html That was the series where I briefly switch from bitmaps to hash and list. However, I see that the fdb code that was playing with never got posted..= . Sorry. -vlad > Thanks, > Nik >=20 >>> >>>>> On the notification side if we can fix that, we can actually delete= the 96000 entries without creating a >>>>> huge notification storm and do a user-land workaround of the origin= al issue, so I=E2=80=99ll look into that next. >>>>> >>>>> Any comments or ideas are very welcome. >>>>> >>>>> Thank you, >>>>> Nik >=20