[19:42:26] [Server thread/WARN] [FML]: Recurrent Complex loaded a new chunk [37, 109] in dimension 0 (overworld) while populating chunk [38, 109], causing cascading worldgen lag.
[19:42:26] [Server thread/WARN] [FML]: Please report this to the mod's issue tracker. This log can be disabled in the Forge config.
[19:43:04] [Server thread/WARN] [FML]: Recurrent Complex loaded a new chunk [32, 110] in dimension 0 (overworld) while populating chunk [33, 110], causing cascading worldgen lag.
[19:43:04] [Server thread/WARN] [FML]: Please report this to the mod's issue tracker. This log can be disabled in the Forge config.
[19:43:09] [Server thread/WARN] [net.minecraft.server.MinecraftServer]: Can't keep up! Did the system time change, or is the server overloaded? Running 2057ms behind, skipping 41 tick(s)
[19:43:10] [Server thread/WARN] [FML]: Recurrent Complex loaded a new chunk [39, 123] in dimension 0 (overworld) while populating chunk [40, 123], causing cascading worldgen lag.
[19:43:10] [Server thread/WARN] [FML]: Please report this to the mod's issue tracker. This log can be disabled in the Forge config.
[19:46:33] [Server thread/WARN] [FML]: Recurrent Complex loaded a new chunk [29, 115] in dimension 0 (overworld) while populating chunk [30, 115], causing cascading worldgen lag.
[19:46:33] [Server thread/WARN] [FML]: Please report this to the mod's issue tracker. This log can be disabled in the Forge config.
[19:46:49] [Server thread/WARN] [FML]: Recurrent Complex loaded a new chunk [28, 122] in dimension 0 (overworld) while populating chunk [29, 122], causing cascading worldgen lag.
[19:46:49] [Server thread/WARN] [FML]: Please report this to the mod's issue tracker. This log can be disabled in the Forge config.
[19:47:22] [Server thread/WARN] [FML]: Recurrent Complex loaded a new chunk [31, 139] in dimension 0 (overworld) while populating chunk [31, 138], causing cascading worldgen lag.
[19:47:22] [Server thread/WARN] [FML]: Please report this to the mod's issue tracker. This log can be disabled in the Forge config.
[19:47:57] [Server thread/WARN] [net.minecraft.network.NetHandlerPlayServer]: IsraYoSoy moved too quickly! -7.572784174669778,-1.0,6.680648068492701
[19:47:58] [Server thread/WARN] [net.minecraft.server.MinecraftServer]: Can't keep up! Did the system time change, or is the server overloaded? Running 2948ms behind, skipping 58 tick(s)
[19:51:13] [Server thread/WARN] [FML]: Recurrent Complex loaded a new chunk [31, 164] in dimension 0 (overworld) while populating chunk [32, 164], causing cascading worldgen lag.
[19:51:13] [Server thread/WARN] [FML]: Please report this to the mod's issue tracker. This log can be disabled in the Forge config.
[19:51:13] [Server thread/WARN] [FML]: Recurrent Complex loaded a new chunk [37, 164] in dimension 0 (overworld) while populating chunk [36, 164], causing cascading worldgen lag.
[19:51:13] [Server thread/WARN] [FML]: Please report this to the mod's issue tracker. This log can be disabled in the Forge config.
[19:51:14] [Server thread/WARN] [FML]: Recurrent Complex loaded a new chunk [38, 164] in dimension 0 (overworld) while populating chunk [37, 164], causing cascading worldgen lag.
[19:51:14] [Server thread/WARN] [FML]: Please report this to the mod's issue tracker. This log can be disabled in the Forge config.
[19:51:15] [Server thread/WARN] [net.minecraft.server.MinecraftServer]: Can't keep up! Did the system time change, or is the server overloaded? Running 2127ms behind, skipping 42 tick(s)
[19:51:16] [Server thread/WARN] [FML]: Recurrent Complex loaded a new chunk [31, 166] in dimension 0 (overworld) while populating chunk [31, 165], causing cascading worldgen lag.
[19:51:16] [Server thread/WARN] [FML]: Please report this to the mod's issue tracker. This log can be disabled in the Forge config.
[19:51:16] [Server thread/WARN] [FML]: Recurrent Complex loaded a new chunk [32, 166] in dimension 0 (overworld) while populating chunk [31, 165], causing cascading worldgen lag.
[19:51:16] [Server thread/WARN] [FML]: Please report this to the mod's issue tracker. This log can be disabled in the Forge config.
[19:51:36] [Server thread/WARN] [FML]: Recurrent Complex loaded a new chunk [32, 169] in dimension 0 (overworld) while populating chunk [33, 169], causing cascading worldgen lag.
[19:51:36] [Server thread/WARN] [FML]: Please report this to the mod's issue tracker. This log can be disabled in the Forge config.
[19:51:36] [Server thread/WARN] [FML]: Recurrent Complex loaded a new chunk [31, 169] in dimension 0 (overworld) while populating chunk [32, 169], causing cascading worldgen lag.
[19:51:36] [Server thread/WARN] [FML]: Please report this to the mod's issue tracker. This log can be disabled in the Forge config.
[19:51:52] [Server thread/WARN] [FML]: Recurrent Complex loaded a new chunk [33, 172] in dimension 0 (overworld) while populating chunk [33, 171], causing cascading worldgen lag.
[19:51:52] [Server thread/WARN] [FML]: Please report this to the mod's issue tracker. This log can be disabled in the Forge config.
[19:51:52] [Server thread/WARN] [FML]: Recurrent Complex loaded a new chunk [34, 171] in dimension 0 (overworld) while populating chunk [33, 172], causing cascading worldgen lag.
[19:51:52] [Server thread/WARN] [FML]: Please report this to the mod's issue tracker. This log can be disabled in the Forge config.
[19:51:52] [Server thread/WARN] [FML]: Recurrent Complex loaded a new chunk [34, 172] in dimension 0 (overworld) while populating chunk [34, 171], causing cascading worldgen lag.
[19:51:52] [Server thread/WARN] [FML]: Please report this to the mod's issue tracker. This log can be disabled in the Forge config.
[19:51:56] [Server thread/WARN] [net.minecraft.server.MinecraftServer]: Can't keep up! Did the system time change, or is the server overloaded? Running 4409ms behind, skipping 88 tick(s)
[19:52:03] [Server thread/WARN] [FML]: Recurrent Complex loaded a new chunk [31, 173] in dimension 0 (overworld) while populating chunk [30, 173], causing cascading worldgen lag.
[19:52:03] [Server thread/WARN] [FML]: Please report this to the mod's issue tracker. This log can be disabled in the Forge config.
[19:52:06] [Server thread/WARN] [FML]: Recurrent Complex loaded a new chunk [37, 173] in dimension 0 (overworld) while populating chunk [36, 173], causing cascading worldgen lag.
[19:52:06] [Server thread/WARN] [FML]: Please report this to the mod's issue tracker. This log can be disabled in the Forge config.
latest.log

See https://www.reddit.com/r/feedthebeast/comments/5x0twz/investigating_extreme_worldgen_lag/ to understand what's going on.

Duplicate of #155