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From: David Ahern <dsahern@gmail.com>
To: Cong Wang <xiyou.wangcong@gmail.com>
Cc: David Miller <davem@davemloft.net>,
	Linux Kernel Network Developers <netdev@vger.kernel.org>,
	nikita.leshchenko@oracle.com,
	Roopa Prabhu <roopa@cumulusnetworks.com>,
	Stephen Hemminger <stephen@networkplumber.org>,
	Ido Schimmel <idosch@mellanox.com>,
	Jiri Pirko <jiri@mellanox.com>,
	Saeed Mahameed <saeedm@mellanox.com>,
	Alexander Aring <alex.aring@gmail.com>,
	linux-wpan@vger.kernel.org,
	NetFilter <netfilter-devel@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH RFC/RFT net-next 00/17] net: Convert neighbor tables to per-namespace
Date: Tue, 24 Jul 2018 09:14:01 -0600
Message-ID: <5021d874-8e99-6eba-f24b-4257c62d4457@gmail.com> (raw)
In-Reply-To: <CAM_iQpW4-JkZY7jXx0Q1b907hQ85UOL1eXv2YHwSukb5L=apUg@mail.gmail.com>

On 7/19/18 11:12 AM, Cong Wang wrote:
> On Thu, Jul 19, 2018 at 9:16 AM David Ahern <dsahern@gmail.com> wrote:
>>
>> Chatting with Nikolay about this and he brought up a good corollary - ip
>> fragmentation. It really is a similar problem in that memory is consumed
>> as a result of packets received from an external entity. The ipfrag
>> sysctls are per namespace with a limit that non-init_net namespaces can
>> not set high_thresh > the current value of init_net. Potential memory
>> consumed by fragments scales with the number of namespaces which is the
>> primary concern with making neighbor tables per namespace.
> 
> Nothing new, already discussed:
> https://marc.info/?l=linux-netdev&m=140391416215988&w=2
> 
> :)
> 

Neighbor tables, bridge fdbs, vxlan fdbs and ip fragments all consume
local memory resources due to received packets. bridge and vxlan fdb's
are fairly straightforward analogs to neighbor entries; they are per
device with no limits on the number of entries. Fragments have memory
limits per namespace. So neighbor tables are the only ones with this
strict limitation and concern on memory consumption.

I get the impression there is no longer a strong resistance against
moving the tables to per namespace, but deciding what is the right
approach to handle backwards compatibility. Correct? Changing the
accounting is inevitably going to be noticeable to some use case(s), but
with sysctl settings it is a simple runtime update once the user knows
to make the change.

neighbor entries round up to 512 byte allocations, so with the current
gc_thresh defaults (128/512/1024) 512k can be consumed. Using those
limits per namespace seems high which is why I suggested a per-namespace
default of (16/32/64) which amounts to 32k per namespace limit by
default. Open to other suggestions as well.

  reply index

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-17 12:06 dsahern
2018-07-17 12:06 ` [PATCH RFC/RFT net-next 01/17] net/ipv4: rename ipv4_neigh_lookup to ipv4_dst_neigh_lookup dsahern
2018-07-17 12:06 ` [PATCH RFC/RFT net-next 02/17] net/neigh: export neigh_find_table dsahern
2018-07-17 12:06 ` [PATCH RFC/RFT net-next 03/17] net/ipv4: wrappers for arp table references dsahern
2018-07-17 12:06 ` [PATCH RFC/RFT net-next 04/17] net/ipv4: Remove open coded use of arp table dsahern
2018-07-17 12:06 ` [PATCH RFC/RFT net-next 05/17] net/ipv6: wrappers for neighbor table references dsahern
2018-07-17 12:06 ` [PATCH RFC/RFT net-next 06/17] net/ipv6: Remove open coded use of neighbor table dsahern
2018-07-17 12:06 ` [PATCH RFC/RFT net-next 07/17] drivers/net: remove open coding of neighbor tables dsahern
2018-07-17 12:06 ` [PATCH RFC/RFT net-next 08/17] net: Remove nd_tbl from ipv6 stub dsahern
2018-07-17 12:06 ` [PATCH RFC/RFT net-next 09/17] net: Remove arp_tbl and nd_tbl from headers dsahern
2018-07-17 12:06 ` [PATCH RFC/RFT net-next 10/17] net: Add key_len to neighbor constructor dsahern
2018-07-17 12:06 ` [PATCH RFC/RFT net-next 11/17] net: Change neigh_table_init and neigh_table_clear signature dsahern
2018-07-17 12:06 ` [PATCH RFC/RFT net-next 12/17] net/neigh: Change neigh_xmit to take an address family dsahern
2018-07-17 12:06 ` [PATCH RFC/RFT net-next 13/17] net/neighbor: Convert internal functions away from neigh_tables dsahern
2018-07-17 12:06 ` [PATCH RFC/RFT net-next 14/17] net/ipv4: Convert arp table to per namespace dsahern
2018-07-17 12:06 ` [PATCH RFC/RFT net-next 15/17] net/ipv6: Convert neighbor table to per-namespace dsahern
2018-07-17 12:06 ` [PATCH RFC/RFT net-next 16/17] net/decnet: Move " dsahern
2018-07-17 12:06 ` [PATCH RFC/RFT net-next 17/17] net/neighbor: Remove neigh_tables and NEIGH enum dsahern
2018-07-17 17:40 ` [PATCH RFC/RFT net-next 00/17] net: Convert neighbor tables to per-namespace Cong Wang
2018-07-17 17:43   ` David Ahern
2018-07-17 17:53     ` Cong Wang
2018-07-17 19:02       ` David Ahern
2018-07-17 20:37         ` Cong Wang
2018-07-18  3:59         ` David Miller
2018-07-19 16:16           ` David Ahern
2018-07-19 17:12             ` Cong Wang
2018-07-24 15:14               ` David Ahern [this message]
2018-07-24 17:14                 ` David Miller
2018-07-25 18:23                   ` David Ahern
2018-07-24 22:09                 ` Cong Wang
2018-07-25 12:33                   ` Eric W. Biederman
2018-07-25 14:06                     ` David Ahern
2018-07-25 17:38                       ` Eric W. Biederman
2018-07-25 18:13                         ` David Ahern
2018-07-25 19:17                           ` Eric W. Biederman
2018-08-13 21:48                             ` David Ahern
2018-08-15  4:36                               ` Eric W. Biederman
2018-07-26 11:12                         ` David Laight
2018-07-27 16:27                           ` Eric W. Biederman
2018-07-19  0:54 ` Michael Richardson
2018-07-19 15:49   ` David Ahern
2018-08-12  6:46 ` [RFC/RFT, net-next, " Vasily Averin
2018-08-12 17:37   ` David Ahern

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