I've had performance problems with garbage collection before, but this profiler output gave me a great giggle:
00000030 6173 2.26089 ipt_do_table_Rsmp_b731682a /lib/modules/2.4.18-26.7.xcustom/kernel/net/ipv4/netfilter/ip_tables.o c01dc450 11798 4.32107 rt_intern_hash /logs/vmlinux 00000000 25777 9.44095 (no symbol) /isd/isdwss/erts-5.2.b1.oprofile/bin/beam c01ddfa0 40883 14.9736 ip_route_input /logs/vmlinux c01d0a60 109002 39.9225 neigh_forced_gc /logs/vmlinux
Time for a generational collector in Linux? :-)
And I must say, oprofile is an unbelievably cool tool. Who says systems software research is irrelevant?
(P.S., that GC expense is provoked by a flood of IP packets with random source addresses.)