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JOURNAL FOR FRIDAY 29TH DECEMBER, 2017
______________________________________________________________________________
SUBJECT: WolfMUD on a Raspberry Pi 3 — part 2
DATE: Fri 29 Dec 19:13:27 GMT 2017
After yesterday’s little experiment[1] with WolfMUD, on a shiny new Raspberry
Pi 3, I had some emails asking me if I could push things further.
So, today I created 20,480 ‘player’ bot accounts to see what this tiny board
could really do. I used the same set up as before, including the same network
tweaks.
All of the ‘player’ bots were again launched from a separate machine — my
desktop. I also set GOMAXPROCS=32 for the server.
The result? The Raspberry Pi 3 was able to handle over 17,500 bots and myself
logged in. I could push the number of bots a little higher, but then I started
to get connection errors, I therefore stayed at 17,500 bots. Some stats from
the server:
U[127Mb -5Mb] O[1340427 +358082] T[17685 +0] G[17513 +0] P 17501/17501
U[122Mb -4Mb] O[ 887502 -452925] T[17685 +0] G[17513 +0] P 17501/17501
U[145Mb +22Mb] O[1144671 +257169] T[17685 +0] G[17513 +0] P 17501/17501
U[164Mb +18Mb] O[1346555 +201884] T[17685 +0] G[17513 +0] P 17501/17501
U[128Mb -36Mb] O[1345709 -846] T[17685 +0] G[17513 +0] P 17501/17501
The statistics line is output every ten seconds by the server. After yesterday
I’ve been asked if I can explain the figures. The ‘U’ column shows the current
memory in use. Above, the server is using between 122Mb and 164Mb RAM as
reported by the Go runtime memory statistics. The ‘O’ column shows the number
of live Go objects. The ‘T’ column is the number of things currently in the
game world. The ‘G’ column show the current number of Goroutines. The ‘P’
column shows the current number of players and the maximum number of players
since the server started.
For each column the +/- figures show the change since the previous statistics
line was output. In this case every ten seconds.
So that’s 17,500 ‘player’ bots and myself — all running around the world — in
122Mb to 164Mb of RAM. Not too shabby!
Some statistics from the top command:
top - 18:13:46 up 31 min, 1 user, load average: 12.88, 7.06, 4.19
Tasks: 123 total, 1 running, 122 sleeping, 0 stopped, 0 zombie
%Cpu0: 48.4 us, 5.9 sy, 0.0 ni, 3.3 id, 0.0 wa, 0.0 hi, 42.4 si, 0.0 st
%Cpu1: 81.9 us, 12.1 sy, 0.0 ni, 6.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
%Cpu2: 82.9 us, 9.9 sy, 0.0 ni, 7.2 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
%Cpu3: 81.2 us, 12.2 sy, 0.0 ni, 6.6 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
MiB Mem : 976.867 total, 350.645 free, 274.820 used, 351.402 buff/cache
MiB Swap: 985.996 total, 985.996 free, 0.000 used. 686.375 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
20247 rolfea 20 1194.0m 181.5m 3.7m S 354.5 18.6 9:57.37 server
There was also a 10-15% CPU usage from my use of SSH with dvtm to access the
server from my desktop.
The little Raspberry Pi did get a little toasty this time. The CPU hit 77.9°C
as reported by the output of running:
/opt/vc/bin/vcgencmd measure_temp
That’s with the Raspberry Pi 3 in a Ninja Coupé PiBow case[2] and with a small
heat sink on the CPU[3].
With some additional tweaks and optimisation could I push things even further?
Could you find me 17,500+ Mud players? ;)
--
Diddymus
[1] Journal for Thursday 28th December, 2017: 28.html
[2] Ninja Coupé PiBow case @ ModMyPi:
https://www.modmypi.com/raspberry-pi/cases-183/raspberry-pi-b-plus2-and-3-cases-1122/plastic-cases-1142/ninja-coup%C3%A9-pibow-raspberry-pi-case--model-b-plus-and-2
[3] Heat sink @ ModMyPi:
https://www.modmypi.com/raspberry-pi/accessories-198/heat-sinks-and-cooling/raspberry-pi-heat-sink-kit-black
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