Minecraft – Will villagers fall to their deaths or exhibit other suicidal behavior

Since version 1.5, this hasn't been much of an issue, as that release introduced a rule in the mobs' AI to avoid rails unless they are chasing after the player. Although I have still found Zombie Pigmen appearing on the tracks, this is now not as much of an issue as it was in previous versions.

Zombie Pigmen are able to spawn on rail tracks, so removing the walking path on the side will do nothing. But as has been mentioned, adding blocks above your tracks will prevent them from spawning and help keep them from walking onto your tracks 100% of the time. This is a common "fix", and has been around for quite a while, and it doesn't seem like the developers have any plans to stop this fix from being possible.

The following blocks can safely be placed above the tracks, and will not suffocate you:

• Glass panes (I would really recommend this one, since they are "cheaper" than glass blocks, works with stained glass panes as well)
• Glass blocks (works with stained glass as well)
• Glowstone blocks
• Leaf blocks
• Iron bars
• Fences (of all materials)
• Half-slabs (of all materials, note that they must be single, NOT double slabs)
• Stairs (of all materials)
• Trap doors
• Pistons (both extended and retracted)

There are other blocks that would work, such as Beds, Chests, TNT, or Enchantment Tables, but I have excluded them from the list due to being impractical.

Other than the typical solutions such as installing optifine, you can also dive deeper into the game mechanics and modify those to improve performance.

Vanilla achieves 'random' growth by selecting several thousand blocks each server tick, checking if they can grow or decay, and if they can, applying the growth or decay. This is the 2nd biggest drain on CPU, behind entities.

Seeing as its a farm... there's going to be a lot of calculations going on.

You can of course reduce this number of blocks per tick by installing Spigot and changing the config there, at the cost of slower growth of your crops on your farm.

There are various options you change to be checked at slower intervals, just a few are:

• Snow form
• Ice melt
• Reducing number of mobs that spawn (those in caves under your farm still use up resources)
• Leaf decay

Of course, upgrading your hardware is probably the most effective solution. It is most likely that the CPU will be your bottleneck, but RAM may also be the issue. Use F3 to check the RAM usage in-game.