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Introduce DXR as an IPv4 longest prefix matching / FIB module

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DXR maintains compressed lookup structures with a trivial search
procedure.  A two-stage trie is indexed by the more significant bits of
the search key (IPv4 address), while the remaining bits are used for
finding the next hop in a sorted array.  The tradeoff between memory
footprint and search speed depends on the split between the trie and
the remaining binary search.  The default of 20 bits of the key being
used for trie indexing yields good performance (see below) with
footprints of around 2.5 Bytes per prefix with current BGP snapshots.

Rebuilding lookup structures takes some time, which is compensated for by
batching several RIB change requests into a single FIB update, i.e. FIB
synchronization with the RIB may be delayed for a fraction of a second.
RIB to FIB synchronization, next-hop table housekeeping, and lockless
lookup capability is provided by the FIB_ALGO infrastructure.

DXR works well on modern CPUs with several MBytes of caches, especially
in VMs, where is outperforms other currently available IPv4 FIB
algorithms by a large margin.

Synthetic single-thread LPM throughput test method:

kldload test_lookup; kldload dpdk_lpm4; kldload fib_dxr
sysctl net.route.test.run_lps_rnd=N
sysctl net.route.test.run_lps_seq=N

where N is the number of randomly generated keys (IPv4 addresses) which
should be chosen so that each test iteration runs for several seconds.

Each reported score represents the best of three runs, in million
lookups per second (MLPS), for two bechmarks (RND & SEQ) with two FIBs:

host: single interface address, local subnet route + default route
BGP: snapshot from linx.routeviews.org, 887957 prefixes, 496 next hops

Bhyve VM on an Intel(R) Xeon(R) CPU E5-2670 0 @ 2.60 GHz:
inet.algo         host, RND    host, SEQ    BGP, RND    BGP, SEQ
bsearch4             40.6         20.2         N/A         N/A
radix4                7.8          3.8         1.2         0.6
radix4_lockless      18.0          9.0         1.6         0.8
dpdk_lpm4            14.4          5.0        14.6         5.0
dxr                  70.3         34.7        43.0        19.5

Intel(R) Core(TM) i5-5300U CPU @ 2.30 GHz:
inet.algo         host, RND    host, SEQ    BGP, RND    BGP, SEQ
bsearch4             47.0         23.1         N/A         N/A
radix4                8.5          4.2         1.9         1.0
radix4_lockless      19.2          9.5         2.5         1.2
dpdk_lpm4            31.2          9.4        31.6         9.3
dxr                  84.9         41.4        51.7        23.6

Intel(R) Core(TM) i7-4771 CPU @ 3.50 GHz:
inet.algo         host, RND    host, SEQ    BGP, RND    BGP, SEQ
bsearch4             59.5         29.4         N/A         N/A
radix4               10.8          5.5         2.5         1.3
radix4_lockless      24.7         12.0         3.1         1.6
dpdk_lpm4            29.1          9.0        30.2         9.1
dxr                 101.3         49.9        69.8        32.5

AMD Ryzen 7 3700X 8-Core Processor @ 3.60 GHz:
inet.algo         host, RND    host, SEQ    BGP, RND    BGP, SEQ
bsearch4             70.8         35.4         N/A         N/A
radix4               14.4          7.2         2.8         1.4
radix4_lockless      30.2         15.1         3.7         1.8
dpdk_lpm4            29.9          9.0        30.0         8.9
dxr                 163.3         81.5        99.5        44.4

AMD Ryzen 5 5600X 6-Core Processor @ 3.70 GHz:
inet.algo         host, RND    host, SEQ    BGP, RND    BGP, SEQ
bsearch4             93.6         46.7         N/A         N/A
radix4               18.9          9.3         4.3         2.1
radix4_lockless      37.2         18.6         5.3         2.7
dpdk_lpm4            51.8         15.1        51.6        14.9
dxr                 218.2        103.3       114.0        49.0

Reviewed by:	melifaro
MFC after:	1 week
Differential Revision: https://reviews.freebsd.org/D29821
This commit is contained in:
Marko Zec 2021-05-05 13:45:52 +02:00
parent a43104ebe7
commit 2aca58e16f
3 changed files with 1266 additions and 0 deletions
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2
sys/modules/Makefile
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@ -120,6 +120,7 @@ SUBDIR= \
fdc \
fdescfs \
${_ffec} \
${_fib_dxr} \
filemon \
firewire \
firmware \
@ -474,6 +475,7 @@ _ipfilter= ipfilter
.if ${MK_INET_SUPPORT} != "no" && ${KERN_OPTS:MFIB_ALGO}
_dpdk_lpm4= dpdk_lpm4
_fib_dxr= fib_dxr
.endif
.if ${MK_INET6_SUPPORT} != "no" && ${KERN_OPTS:MFIB_ALGO}

11
sys/modules/fib_dxr/Makefile Normal file
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@ -0,0 +1,11 @@
# $FreeBSD$
SYSDIR?=${SRCTOP}/sys
.include "${SYSDIR}/conf/kern.opts.mk"
.PATH: ${SYSDIR}/netinet
KMOD= fib_dxr
SRCS= in_fib_dxr.c opt_inet.h
.include <bsd.kmod.mk>

1253
sys/netinet/in_fib_dxr.c Normal file
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