Redstone and item pickup are very slow.

I downloaded your world save and the redstone is working at proper speeds for me. Perhaps your computer has lag?

Please attach the complete output of the "Development console" which can be found on the second tab of the launcher.

If the launcher closes after game start, please edit your profile and select "Launcher visibility" then, "Keep the launcher open".

I've uploaded the world with the command blocks that cause the problem.

It seems that activating the command blocks in the "Command blocks" world causes the game to stall whenever redstone is activated, giving a "Can't keep up!" message and causing the game to skip an amount of ticks.

Aside from the server stalling, there's nothing abnormal in the log

Is this still an issue in 14w28b ?

At least the "Item pickup delay" is still an issue in 14w30c.

Is this still a concern in the current Minecraft version? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases. If this has been done, we can reopen the issue.

Keep in mind that the "Resolved"-Status on this ticket just means "Answered", and that we are waiting for further information on whether this issue still exists or not. We will reopen it as soon as the requested information has been delivered.

Confirmed for 15w45a

Java: Java 8 update 65 (F3 states that it's update 25, not true)
OS: Windows 10 64 bit

Here's a link to the video: https://drive.google.com/file/d/0BwXwob6hmy8-ZkJwOVJQdUU3OUU/view?usp=sharing

Edit 01: And here is the world: https://drive.google.com/file/d/0BwXwob6hmy8-cGlsNUdvSkI2WVE/view?usp=sharing

Edit 02: The .log.gz with the numbers is only openable with WinRAR... Sorry

@@unknown: this was an issue specific to 14w25b to 14w31a