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ArqadeJava uses all CPU while playing Minecraft
[+4] [4] gumbo
[2011-08-13 14:59:00]
[ minecraft-java-edition technical-issues linux ]
[ https://gaming.stackexchange.com/questions/27849/java-uses-all-cpu-while-playing-minecraft ]

I recently purchased Minecraft, but after I have been playing for about 5-10 minutes, the Java process uses all CPU power, leading to a sudden shutdown.

This is weird, because some months ago it ran without any problems.

Is there any way to fix this?

My OS is Ubuntu 11.04.

(1) What level of graphics are you using? Try turning it down to Fast. - ChrisF
Also try reducing every other graphics option to the minimum. - John the Green
(1) duplicate of gaming.stackexchange.com/questions/21373/… and gaming.stackexchange.com/questions/26113/… - Cyclops
I have seen this problem on Windows too. In that case it was an old JVM and updating it fixed the problem. Minecraft's stability seems very sensitive to the JVM. On Ubuntu even if your JVM is up-to-date you have two to choose from OpenJDK and Sun's JVM. - SevenSidedDie
@Cyclops not a duplicate because the sudden shut down was due to excesive tº of CPU because of the intensive use java was doing of it, and it only happened once - gumbo
[+8] [2011-08-13 15:52:35] Stefan Bossbaly [ACCEPTED]

I am using Ubuntu too here are a couple of questions and suggestions ...

1) Are you using the open JDK? If you install sun's JDK and run the command sudo update-alternatives --config java and select Sun's JDK.

2) What speed is your processor and how many cores and how much RAM do you have? You might to specficy some command parameters when you run minecraft. Try giving minecraft more RAM by using the -Xmx and -Xms to give Minecraft more RAM at startup. You can read more about that here [1]. For example the command I use is java -Xmx5000m -Xms5000m -jar minecraft.jar

3) Try turning down your video settings. Turn down the render distance and switch the graphics settings to Fast.

[1] http://javahowto.blogspot.com/2006/06/6-common-errors-in-setting-java-heap.html

2) is what worked for me, but instead of -Xmx5000m I used java -Xmx1024M -Xms512M -jar minecraft.jar - gumbo
@gumbo Yup that will work. I have 6 gigs of RAM so I just set it to some high value so the system doesn't garbage collect chunks. - Stefan Bossbaly
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[+1] [2011-10-01 05:31:16] febs

I just had this exact problem with a fresh 11.04, setting up the Sun JDK was a doozie, and even then my CPU was spiking over 100% usage, whoa! I could hear the clock in my headphones

Here where my steps to solve it:

  1. Go to synaptic, enable the Canonical Partners repos (the two unchecked boxes)
  2. completely remove the open jdk and jre.
    • You should be prompted to mark the Sun JDK/JRE for install
  3. Install
  4. java -version in a terminal you should get: Java(TM) SE Runtime Environment instead of the OpenJDK
  5. Try to fire up minecraft with java -Xmx1024M -Xms512M -cp minecraft.jar net.minecraft.LauncherFrame
  6. At this point I was noticing the insane CPU usage when adding multiplayer servers (weird). On the main menu in options -> Video Settings change performance to Power Saver

I was stunned that this worked. I remember my old dell laptop had a CPU clock issue where I could hear the high freq in my headphones, the solution was to underclock the processor to get rid of the noise. Pretty cool, it's like underclocking the JVM or telling it to be more sparring with the CPU (which in this case solved made everything run smoothly)

Hope this helps someone


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[0] [2011-08-13 15:40:24] ChrisF

I get a similar problem on Windows 7 if I select "Fancy" graphics.

Selecting "Fast" allows me to play for as long as I like.


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[0] [2013-05-01 01:15:44] user47837

No guys, this is a confirmed bug in Minecraft with Linux. Even on an extremely powerful system using < 400MB of 4 GB of allocated memory, Minecraft will play wonderfully and then suddenly drop to 0 FPS and cause the whole X server to lag. Once closed, everything comes back to normal.

No known fix as of yet.

https://mojang.atlassian.net/browse/MC-2258


You say it's a "confirmed" bug, but I'm looking at that bug submission in the Mojang bug tracker and it's not confirmed or even accepted by Mojang yet. What definition of "confirmed" are you using? - SevenSidedDie
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