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diff --git a/docs/developer/corefeatures/fib/scale.rst b/docs/developer/corefeatures/fib/scale.rst new file mode 100644 index 00000000000..2ec8c6a85ec --- /dev/null +++ b/docs/developer/corefeatures/fib/scale.rst @@ -0,0 +1,247 @@ +.. _scale: + +Scale +----- + +The only limiting factor on FIB scale is the amount of memory +allocated to each heap the FIB uses, and there are 2: + +* The main heap +* The stats heap + + +Main Heap +^^^^^^^^^ + +The main heap is used to allocate all memory needed for the FIB +data-structures. Each table, created by the user, i.e. with; + +.. code-block:: console + + $ ip table add 1 + +or the default table, comprises 2 *ip4_fib_t* objects. +The 'non-forwarding' *ip4_fib_t* contains all the entries in the table +and, the 'forwarding' contains the entries that are matched against in +the data-plane. The difference between the two sets are the entries +that should not be matched in the data-plane. +Each *ip4_fib_t* comprises an mtrie (for fast lookup in the data-plane) +and a hash table per-prefix length (for lookup in the control plane). + +To see the amount of memory consumed by the IPv4 tables use: + +.. code-block:: console + + vpp# sh ip fib mem + ipv4-VRF:0 mtrie:335744 hash:4663 + ipv4-VRF:1 mtrie:333056 hash:3499 + totals: mtrie:668800 hash:8162 all:676962 + +this output shows two 'empty' (i.e. no added routes) tables. Each +mtrie uses about 150k of memory, so each table about 300k. + + +Below the output having added 1M, 2M and 4M routes respectively: + +.. code-block:: console + + vpp# sh ip fib mem + ipv4-VRF:0 mtrie:335744 hash:4695 + totals: mtrie:335744 hash:4695 all:340439 + +.. code-block:: console + + vpp# sh ip fib mem + ipv4-VRF:0 mtrie:5414720 hash:41177579 + totals: mtrie:5414720 hash:41177579 all:46592299 + +.. code-block:: console + + vpp# sh ip fib mem + ipv4-VRF:0 mtrie:22452608 hash:168544508 + totals: mtrie:22452608 hash:168544508 all:190997116 + + +IPv6 also has the concept of forwarding and non-forwarding entries, +however for IPv6 all the forwarding entries are stored in a single +hash table (same goes for the non-forwarding). The key to the hash +table includes the IPv6 table-id. + +To see the amount of memory consumed by the IPv4 tables use: + +.. code-block:: console + + vpp# sh ip6 fib mem + IPv6 Non-Forwarding Hash Table: + Hash table ip6 FIB non-fwding table + 7 active elements 7 active buckets + 1 free lists + 0 linear search buckets + arena: base 7f2fe28bf000, next 803c0 + used 525248 b (0 Mbytes) of 33554432 b (32 Mbytes) + + IPv6 Forwarding Hash Table: + Hash table ip6 FIB fwding table + 7 active elements 7 active buckets + 1 free lists + 0 linear search buckets + arena: base 7f2fe48bf000, next 803c0 + used 525248 b (0 Mbytes) of 33554432 b (32 Mbytes) + +as we scale to 128k IPv6 entries: + +.. code-block:: console + + vpp# sh ip6 fib mem + IPv6 Non-Forwarding Hash Table: + Hash table ip6 FIB non-fwding table + 131079 active elements 32773 active buckets + 2 free lists + [len 1] 2 free elts + 0 linear search buckets + arena: base 7fed7a514000, next 4805c0 + used 4720064 b (4 Mbytes) of 1073741824 b (1024 Mbytes) + + IPv6 Forwarding Hash Table: + Hash table ip6 FIB fwding table + 131079 active elements 32773 active buckets + 2 free lists + [len 1] 2 free elts + 0 linear search buckets + arena: base 7fedba514000, next 4805c0 + used 4720064 b (4 Mbytes) of 1073741824 b (1024 Mbytes) + +and 256k: + +.. code-block:: console + + vpp# sh ip6 fib mem + IPv6 Non-Forwarding Hash Table: + Hash table ip6 FIB non-fwding table + 262151 active elements 65536 active buckets + 2 free lists + [len 1] 6 free elts + 0 linear search buckets + arena: base 7fed7a514000, next 880840 + used 8915008 b (8 Mbytes) of 1073741824 b (1024 Mbytes) + + IPv6 Forwarding Hash Table: + Hash table ip6 FIB fwding table + 262151 active elements 65536 active buckets + 2 free lists + [len 1] 6 free elts + 0 linear search buckets + arena: base 7fedba514000, next 880840 + used 8915008 b (8 Mbytes) of 1073741824 b (1024 Mbytes) + +and 1M: + +.. code-block:: console + + vpp# sh ip6 fib mem + IPv6 Non-Forwarding Hash Table: + Hash table ip6 FIB non-fwding table + 1048583 active elements 65536 active buckets + 4 free lists + [len 1] 65533 free elts + [len 2] 65531 free elts + [len 4] 9 free elts + 0 linear search buckets + arena: base 7fed7a514000, next 3882740 + used 59254592 b (56 Mbytes) of 1073741824 b (1024 Mbytes) + + IPv6 Forwarding Hash Table: + Hash table ip6 FIB fwding table + 1048583 active elements 65536 active buckets + 4 free lists + [len 1] 65533 free elts + [len 2] 65531 free elts + [len 4] 9 free elts + 0 linear search buckets + arena: base 7fedba514000, next 3882740 + used 59254592 b (56 Mbytes) of 1073741824 b (1024 Mbytes) + +as can be seen from the output the IPv6 hash-table in this case was scaled +to 1GB and 1million prefixes has used 56MB of it. + +The main heap is also used to allocate objects that represent the FIB +entries in the control and data plane (see :ref:`controlplane` and +:ref:`dataplane`) such as *fib_entry_t* and *load_balance_t*. These come +from the main heap because they are not protocol specific +(i.e. they are used to represent either IPv4, IPv6 or MPLS +entries). + +With 1M prefixes allocated the memory usage is: + +.. code-block:: console + + vpp# sh fib mem + FIB memory + Tables: + SAFI Number Bytes + IPv4 unicast 1 33619968 + IPv6 unicast 2 118502784 + MPLS 0 0 + IPv4 multicast 1 1175 + IPv6 multicast 1 525312 + Nodes: + Name Size in-use /allocated totals + Entry 72 1048589/ 1048589 75498408/75498408 + Entry Source 40 1048589/ 1048589 41943560/41943560 + Entry Path-Extensions 76 0 / 0 0/0 + multicast-Entry 192 6 / 6 1152/1152 + Path-list 40 18 / 18 720/720 + uRPF-list 16 14 / 14 224/224 + Path 72 22 / 22 1584/1584 + Node-list elements 20 1048602/ 1048602 20972040/20972040 + Node-list heads 8 24 / 24 192/192 + +and with 2M + +.. code-block:: console + + vpp# sh fib mem + FIB memory + Tables: + SAFI Number Bytes + IPv4 unicast 1 33619968 + IPv6 unicast 2 252743040 + MPLS 0 0 + IPv4 multicast 1 1175 + IPv6 multicast 1 525312 + Nodes: + Name Size in-use /allocated totals + Entry 72 2097165/ 2097165 150995880/150995880 + Entry Source 40 2097165/ 2097165 83886600/83886600 + Entry Path-Extensions 76 0 / 0 0/0 + multicast-Entry 192 6 / 6 1152/1152 + Path-list 40 18 / 19 720/760 + uRPF-list 16 18 / 18 288/288 + Path 72 22 / 23 1584/1656 + Node-list elements 20 2097178/ 2097178 41943560/41943560 + Node-list heads 8 24 / 24 192/192 + +However, the situation is not a simple as that. All of the 1M prefixes +added above were reachable via the same next-hop, so the path-list +(and path) they use is shared. As prefixes are added that use +different (sets of) next-hops, the number of path-lists and paths +requires will increase. + + +Stats Heap +^^^^^^^^^^ + +VPP collects statistics for each route. For each route VPP collects +byte and packet counters for packets sent to the prefix (i.e. the +route was matched in the data-plane) and packets sent via the prefix (i.e. the +matching prefix is reachable through it - like a BGP peer). This +requires 4 counters per route in the stats segment. + +Below shows the size of the stats segment with 1M, 2M and 4M routes. + +.. code-block:: console + + total: 1023.99M, used: 127.89M, free: 896.10M, trimmable: 830.94M + total: 1023.99M, used: 234.14M, free: 789.85M, trimmable: 668.15M + total: 1023.99M, used: 456.83M, free: 567.17M, trimmable: 388.91M + |