Bukkit

What steps will reproduce the problem?
Generate any large section (Seems to happen especially on anything greater than 300 sections)
Testing was done on an empty server with 8gb of RAM and a dual-core 2.4 GHz cpu.

What is the expected output? What do you see instead?
As the process works, the map will begin generating slower and slower and consume more and more ram, rather than giving it back as it works (memory leak?).
Early on, generations will happen about once every 3-5 seconds (per section).  As time goes on, it will start taking more and more time (over 1 min per section).
CPU load throughout the process remains at roughly 50-60% throughout.
In this particular test, first, 400 sections were generated with no errors, then 625 (slowly).  Once the 625 were complete, ~1444 began to generate at a normal rate.

If the process pauses because it has hit the memory limit, it will hang there for a seemingly indefinite time (again, memory leak?).

What version of the product are you using?
2.5

Do you have an error log of what happened?
The logs show the following error log.  This error DID NOT show in the console, ONLY in the server.log file.  The console showed normal activity.

2011-11-22 20:04:20 [SEVERE] java.util.ConcurrentModificationException
2011-11-22 20:04:20 [SEVERE]     at java.util.HashMap$HashIterator.nextEntry(HashMap.java:848)
2011-11-22 20:04:20 [SEVERE]     at java.util.HashMap$KeyIterator.next(HashMap.java:883)
2011-11-22 20:04:20 [SEVERE]     at net.minecraft.server.World.a(World.java:2334)
2011-11-22 20:04:20 [SEVERE]     at net.minecraft.server.ChunkLoader.a(SourceFile:140)
2011-11-22 20:04:20 [SEVERE]     at net.minecraft.server.ChunkRegionLoader.a(SourceFile:84)
2011-11-22 20:04:20 [SEVERE]     at net.minecraft.server.ChunkProviderServer.saveChunk(ChunkProviderServer.java:152)
2011-11-22 20:04:20 [SEVERE]     at com.bergerkiller.bukkit.nolagg.ChunkOperation.execute(ChunkOperation.java:140)
2011-11-22 20:04:20 [SEVERE]     at com.bergerkiller.bukkit.nolagg.ChunkScheduler.run(ChunkScheduler.java:137)

Full log file here: http://dl.dropbox.com/u/39648316/server.log
There WILL be a few unrelated errors, due to running a few dev builds and abandoned plugins.

I have generated some *massive* regions without running out of memory - however, there are many CraftBukkit memory leaks that have come and gone, which are more than likely to blame.

If you know what you're doing, look into using jhat/jheap to see what is being leaked - I suspect, strongly, that you're seeing a leak in CraftBukkit.

Also, anyone having memory leak issues, please be sure to include the exact CB build you're using.