Run Bukkit with more RAM!!!

[TechnicMania]

I'm not sure if this will actually work for anyone else, but I'll explain what I'm talking about anyway. The specs on the system I currently use are as follows:

- Intel Core 2Duo 2.9Ghz Dual Core

- 8GB 1600Mhz RAM Quad Kit (2x Dual Channel config)

- 1x 260Gb HDD, 1x 500Gb HDD

- Unknown ACER Mobo

Now, in bukkit I have set the minimum RAM value to 9Gb and the max to 13Gb. "How does this work?" you say? Well, I have 15Gb of pagefile. I noticed, in task manager, that when I launched the server, only 2.5Gb of RAM was in use, but 10Gb of pagefile was in use. Even though this isn't RAM, it's still able to run the server considerably faster. Does anyone else care to try this out and report their findings back to me? I want to see if giving the system more pagefile then increasing the RAM allocation would make it faster again. Ideas, help, suggestion? Care to try this out for me? Any help and findings on this matter would be appreciated.

[disconsented]

So what happens when the servers actual memory usage gets to 9GB?

I bet your system freezes unless Java crashes first.

[plowmanplow]

From a system management perspective, unless you have some very specific/unique processing requirements (of which Forge/MC does not qualify) you should NEVER see active use of your swap space. For a desktop system, maybe. If you have dozens and dozens of things open you can only really "look" at a few things at once. The stuff that gets paged out may be a lot less important. On a server? Not so much. If you are paging things to swap (again with an exception being made for some very uncommon edge cases) you are going to have a bad time.

 

In this case, say you do have 8G physical and 13G allocated by utilizing swap. Assuming you are running Windows, as soon as you go over 6.5G of ACTUAL memory usage by the JVM you are going to start swapping and having a very bad time. However, 13G would be enough to host dozens of people concurrently. If you only have a few people on at once then what is getting swapped is stuff that isn't being actively used. You would see MUCH better results by drastically reducing your alocation for the Forge/MC server process. I have had 15 people actively using a very complex, current modpack (~135 mods reported, mostly tech and worldgen) with the server only having a -Xmx3G with no problems. The only thing that ever drops the TPS is worldgen, and that's a common issue largely unrelated to memory usage.

[rcmaehl]

Swap (aka Disk):

    Maximum speeds:

        (Assuming PATA UDMA): 1.3 Gbit / s (Why does this even still exist on desktop PCs?)

        (Assuming SATA 1         ): 1.5 Gbit / s

        (Assuming SATA 2         ): 3 Gbit / s (This is most likely what you're running)

        (Assuming SATA 3         ): 6 Gbit / s

        (Assuming SATA 3.2      ): 16 Gbit / s

 

RAM:

    Maximum speeds:

        (Assuming DDR1 PC-1600    ): 12.5 Gbit / s

        (Assuming DDR2 PC2-3200  ): 25 Gbit / s

        (Assuming DDR2 PC2-8500  ): 67 Gbit / s

        (Assuming DDR3 PC3-6400  ): 50 Gbit / s

        (Assuming DDR3 PC3-12800): 100 Gbit / s (This is your RAM)

        (Assuming DDR3 PC3-17000): 133 Gbit / s

 

 

And you're telling me:

 

3 > 100

 

The only way this would work:

 

1. You have a magical motherboard that is using some of the worst RAM

2. Your magical motherboard supports the best SATA known to man right now

3. Your magical motherboard isn't bottlenecking

4. Your magical motherboard comes with a magical SATA 3.2 Solid State Disk Drives

 

In Conclusion:

 

I will believe in magic way before I even consider the idea the SWAP would be faster than RAM.

Edited March 4, 2014 by rcmaehl

[freakachu]

gonna add to the chorus of "this isn't as great an idea as you think".  the only reason it's "working" is because of how java actually handles memory.  basically, you're getting lucky without knowing it, which won't last forever.

[TechnicMania]

how long will it last? Will it last when the server actually goes public? because at the moment I'm developing the world and debugging plugins.... how long will it be good for? Because I have noticed (through task manager), that even when I launch it with allocation of 3G, page file is still being used by about 2Gb and the RAM is only being used by about 1Gb... What if I had SSDs, would using page file actually help more than spindle drives?

[rcmaehl]

how long will it last? Will it last when the server actually goes public? because at the moment I'm developing the world and debugging plugins.... how long will it be good for? Because I have noticed (through task manager), that even when I launch it with allocation of 3G, page file is still being used by about 2Gb and the RAM is only being used by about 1Gb... What if I had SSDs, would using page file actually help more than spindle drives?

 

There's a 50% chance your luck may, or may not, last you, at maximum, with all figures calculated, rounded, a week, plus or minus 6 billion femtoseconds.

Edited March 4, 2014 by rcmaehl

[TechnicMania]

so would I be better off putting it down to maybe min of 3Gb max of 5Gb? Would the page file usage slip over to RAM usage once it becomes active? What will happen?

[freakachu]

so would I be better off putting it down to maybe min of 3Gb max of 5Gb? Would the page file usage slip over to RAM usage once it becomes active? What will happen?

the page file will be getting some use pretty much regardless of what you do, but that is unrelated to the server.  windows puts stuff in there all the time for all kinds of reasons.  I wouldn't focus on it too much.

[TechnicMania]

So where would you guys suggest putting the gig limits? My computer has 8Gb of RAM, and I currently have a total of 15Gb of page file available. What should I set the limits to?

[freakachu]

again, forget about pagefile and only deal with physical ram.  3-4 gigs should be sufficient.  only raise it higher if you start seeing a need for it.

[TechnicMania]

Thank you for clearing all this up. So don't worry about the pagefile, just set it to around 3-4 gigs. Cheers to everybody's input!!