RaspberryPi - Questions

[ThuGie]

Hey guys,

I am finally thinking of getting myself a raspi!
Yes kinda late but still.

Now, since my main pc is mostly working again,
Still need to finish some stuff up, i plan to work on some stuff mc related.

And i plan to use the raspi to do that on.

Now, if i recall since raspi has some lag issues with mc, and the amount of players it supports.
What is it that limits the amount of players ram or cpu ?
And what causes most lag ?

I do not plan to generate anything, simple static, read-only worlds will be used.
I do assume that causes the most lag.

Will that indeed solve most lag issues ?
It should also help a bit with the ram i assume, as i plan to keep the worlds quite smallish.

So how many players would mc be able to host on something like this,
Of course i ordered the cooling etc for the pi, and plan to overclock it to if i recall the cap is 1ghz ?
For ram i have not quite found a nice solution to extend on it.
There seems to be something like zram, that compresses/uncompresses on the fly,
But of course we would need more cpu power.. probably slowing things down again causing lag.

https://extremeshok.com/1457/raspberry-p...ng-memory/ for zram information.

Now, i highly doubt i will be able to get a easy and go answer to all of this haha.
But i have noticed quite a few people been playing with the raspi,
And probably have been trying out different things to decrease lag, and increase the amount of players.

Thanks in advance.

Extra, seems after some searching, you are able to overclock the raspi higher then 1ghz, just need some quite good cooling.. any tips on this ?
What have you clocked it to and what are you using to cool it while it still being able to run stable ?

[NiLSPACE]

We managed to have around 5 people online on the Gallery server without any lagg. We didn't try any more people because there weren't any other people available so it could possible be more.

The world generating is indeed the part that causes the most lagg so it's smart to have either a really simple world generator or have a pre-generated map.

[ThuGie]

Hey,

Well i do plan to use pre-made maps, as i plan to be working on creating some mini games.
The plugin api of mcserver is coming along quite nice so, would be a shame not be using it right ?

Hope xoft has some statics of his raspi :p, on how much ram cpu it uses average when there are 5 people online.

Seems i also went up in joy to soon...
BSOD.. just a few seconds ago... seems video driver related but still it gave me a shock :p.
As its pretty much a new pc.. just with old hdd + ram, octa core has different slot then my quad core.
So somehow i ended up with a new pc..
From power supply being kinda outdated, to the new one not fitting in the case, to getting a new case etc etc..
Nice part is i wasn't charged extra. also got a extra sata hdd 160gb + 4gb ram. to make a home server with my old pc :p.

But that's for different stuff then raspi :p.
But might need to reinstall win 8.1 anyway as it simply worked right out the box on the new system after moving the hdd over.
Only needed to reset the cpu count. but i feel it isnt matching the speed i should be getting, so ordered a ssd that should fix it all :p.
And instead cloning it over, i will do a fresh install and use this one as second hdd to store stuff.

I went so off-topic btw..

[xoft]

So much text, so little sense

As for the RasPi, I don't have any hard statistics, only some minor experience from running the Gallery server. It uses about 200 MiB of RAM with 5 players connected, and all the CPU it can get. It is still possible to use the Pi otherwise, though, it will just slow down the server a bit. I normally compile a new version of the server while the old version is still running; the chunks load a bit slower, but other than that there's no difference on the gameplay.
Note, though, that the Gallery server is somewhat different to your normal minecraft server - it has no mobs, it kills most entities before spawning, the redstone and fluid physics are turned off, it has almost zero terrain generation costs and the players have been allocated a smaller view distance - just about everything to make it running smoothly even on a RasPi. You can see for yourself what it feels like, connect to gallery.xoft.cz

[ThuGie]

Hey,

Yeah.. that happens when i am tired and am having a migraine,
So the limiting factor is by far the cpu, have you overclocked it ?

Also redstone,generation,mobs? should also be disabled for me.
Though view distance will probably stay the same.

What is it on your server that uses up most cpu ?

[xoft]

I haven't really done any measurements, although I plan to later on, on my second RasPi. I do know that the lighting thread runs rather slow on ARMs, there's already a github issue for that. Also the mob code could be much improved (it currently collects a mob census on every world tick, instead of keeping the census and updating it when mobs are spawned / destroyed.

I haven't overclocked my RasPi, because it runs 24/7 and I was concerned with damage due to prolonged CPU stress. Also there doesn't seem to be any need for the overclocking, the server does run nicely.

I suppose the best way to find out is to try it out for yourself, I do believe that the server should be usable for 5 players.

---

Oookay, did some basic measurements. Without any players, the server is using 3 % CPU and 170 MiB of memory (most of it probably already committed to chunks and unloaded yet). When a player connects, the server spikes into 100 % CPU for a short while (3 seconds), possibly because of all the chunks that are being streamed to the client. Then the CPU sits at 10 % while the player moves around little, occasionally going up to 60 % when a few new chunks need to be loaded and sent to the client. THe RAM usage stays within the 170 - 180 MiB margin all the time, confirming the primary suspicion of already-committed memory.

[ThuGie]

I see,
So now mobs will probably be disabled on my server, but the lighting is slow as you said,
But lighting should not be needed for static maps right ? is there a option to disable this ?
I mostly plan to have a pre-made world where pretty much nothing in the world changes, except the players that move and open chests etc.
No block updates except interaction with blocks is done, aka chest,furnace, and i am fine with the light not updating for furnace as its always day time.

If there is no such option is it possible to add this ?

[xoft]

Lighting is only calculated when needed, so if there are no changes and the light is (pre)calculated in the chunks already, then it won't need recalculating again. If it isn't precalculated in the chunks, then it will be calculated just once, not much of a burden.

There is no option to disable lighting calculation and I don't think it's of any use to make such option, exactly because of the above reasons.

[ThuGie]

Yeah indeed if that is the case there should be no need,
Is there a way to lessen the burden of sending chunks ?
Like you said when it sends chunks the cpu spikes even if its for a while.

This could still cause lag for other players, is there a way to input a delay of sorts to keep the cpu low/stable ?
Like a trade-off between loading speed and cpu ?

Want to be able to adjust anything i might need to get the max out of the raspi.
btw redstone will also be disabled if this option still exists.

[xoft]

We didn't see any kind of lag to the players caused by loading / sending, other than that the chunks were actually delivered a bit later. This should really pose no problems for you. Really, go have a look at the Gallery server and you'll see how it performs; and while you're there, build something