Limit Obfs4 bridge CPU usage

Support Relay Operator
1

My best obfs4 bridge (100-150 users on the last 6months) is not working anymore because the VPS was suspended due to FUP for CPU.

Please let me know how i can limit the number of users to 80 let’s say or how to limit the process cpu usage to 50%

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2

One technique I’ve used in the past when I had to limit CPU was to use the cpulimit utility.

As an example, I had this saved in case I needed to use it again at some point:
sudo cpulimit -P /usr/sbin/tor -b -c 1 -l 50 -m

This is what I used to invoke tor and limit cpu usage to 50%. You may have to play with it a little to get it working on your system (e.g. changing the path, or percentage) but should be enough to try some things out.

Looking at the command again, not sure why I used the -m parameter as the manual seems to suggest it shouldn’t be used in most cases - but I had it there for a reason and I don’t recall why, perhaps as it was a system dedicated to running tor and I didn’t care about accidently limiting other processes? Unknown.

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3

Thanks for the advice but something goes wrong.

root@s15280 ~ # whereis tor
tor: /usr/bin/tor /usr/sbin/tor /etc/tor /usr/share/tor /usr/share/man/man1/tor.1.gz

root@s15280 ~ # sudo cpulimit -P /usr/sbin/tor -b -c 1 -l 50 -m
root@s15280 ~ # Warning: no target process found. Waiting for it…
root@s15280 ~ # sudo cpulimit -P /usr/bin/tor -b -c 1 -l 50 -m
root@s15280 ~ # Process 478 detected

After i run the cpulimit command a lot of cpulimit instances are starting and are abussing the CPU more than without cpulimit

image
image902×485 27.1 KB

root@s15280 ~ # top
top - 11:14:06 up 8:36, 1 user, load average: 184.13, 95.16, 40.32
Tasks: 426 total, 108 running, 318 sleeping, 0 stopped, 0 zombie
%Cpu(s): 15.4 us, 61.4 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 1.9 si, 21.3 st
MiB Mem : 979.0 total, 247.4 free, 695.4 used, 36.2 buff/cache
MiB Swap: 1024.0 total, 958.1 free, 65.9 used. 195.6 avail Mem

PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND

5481 root 9 -11 76260 128 0 D 0.9 0.0 0:01.14 cpulimit
479 debian-+ 20 0 1327148 59372 0 S 0.7 5.9 50:16.56 obfs4proxy
5641 root 9 -11 76260 132 0 S 0.7 0.0 0:00.39 cpulimit
5426 root 9 -11 76260 380 248 S 0.6 0.0 0:01.36 cpulimit
5429 root 9 -11 76260 128 0 D 0.6 0.0 0:01.34 cpulimit
5431 root 9 -11 76260 128 0 D 0.6 0.0 0:01.37 cpulimit
5433 root 9 -11 76260 356 224 D 0.6 0.0 0:01.30 cpulimit
5435 root 9 -11 76260 128 0 D 0.6 0.0 0:01.33 cpulimit
5440 root 9 -11 76260 376 244 D 0.6 0.0 0:01.32 cpulimit
5444 root 9 -11 76260 128 0 D 0.6 0.0 0:01.24 cpulimit
5447 root 9 -11 76260 128 0 D 0.6 0.0 0:01.25 cpulimit
5448 root 9 -11 76260 368 236 D 0.6 0.0 0:01.28 cpulimit
5449 root 9 -11 76260 336 204 S 0.6 0.0 0:01.28 cpulimit
5451 root 9 -11 76260 368 236 D 0.6 0.0 0:01.29 cpulimit
5455 root 9 -11 76260 368 236 D 0.6 0.0 0:01.22 cpulimit
5456 root 9 -11 76260 128 0 D 0.6 0.0 0:01.24 cpulimit
5466 root 9 -11 76260 368 236 S 0.6 0.0 0:01.17 cpulimit
5468 root 9 -11 76260 372 240 D 0.6 0.0 0:01.17 cpulimit
5471 root 9 -11 76260 380 248 D 0.6 0.0 0:01.20 cpulimit
5472 root 9 -11 76260 368 236 S 0.6 0.0 0:01.19 cpulimit
5473 root 9 -11 76260 128 0 D 0.6 0.0 0:01.19 cpulimit
5474 root 9 -11 76260 376 244 D 0.6 0.0 0:01.22 cpulimit
5475 root 9 -11 76260 372 244 D 0.6 0.0 0:01.17 cpulimit
5479 root 9 -11 76260 376 244 S 0.6 0.0 0:01.13 cpulimit
5480 root 9 -11 76260 372 240 D 0.6 0.0 0:01.13 cpulimit
5484 root 9 -11 76260 356 224 D 0.6 0.0 0:01.12 cpulimit
5489 root 9 -11 76260 124 0 S 0.6 0.0 0:01.08 cpulimit
5509 root 9 -11 76260 372 236 S 1.0 0.0 0:01.02 cpulimit
5512 root 9 -11 76260 132 0 S 1.0 0.0 0:00.98 cpulimit
5513 root 9 -11 76260 372 236 S 1.0 0.0 0:00.96 cpulimit
5519 root 9 -11 76260 376 240 S 1.0 0.0 0:00.92 cpulimit
5530 root 9 -11 76260 380 244 S 1.0 0.0 0:00.88 cpulimit
5531 root 9 -11 76260 132 0 S 1.0 0.0 0:00.88 cpulimit
5540 root 9 -11 76260 360 224 S 1.0 0.0 0:00.86 cpulimit
5547 root 9 -11 76260 372 236 S 1.0 0.0 0:00.78 cpulimit
5555 root 9 -11 76260 376 240 S 1.0 0.0 0:00.79 cpulimit
5557 root 9 -11 76260 132 0 S 1.0 0.0 0:00.75 cpulimit
5565 root 9 -11 76260 380 244 S 1.0 0.0 0:00.73 cpulimit
5568 root 9 -11 76260 372 236 S 1.0 0.0 0:00.77 cpulimit
5573 root 9 -11 76260 376 240 S 1.0 0.0 0:00.71 cpulimit
5581 root 9 -11 76260 136 0 S 1.0 0.0 0:00.64 cpulimit
5589 root 9 -11 76260 372 236 S 1.0 0.0 0:00.58 cpulimit
5597 root 9 -11 76260 308 172 S 1.0 0.0 0:00.57 cpulimit
5611 root 9 -11 76260 136 0 S 1.0 0.0 0:00.50 cpulimit
5616 root 9 -11 76260 340 204 S 1.0 0.0 0:00.50 cpulimit
5625 root 9 -11 76260 372 236 S 1.0 0.0 0:00.42 cpulimit
5627 root 9 -11 76260 372 236 S 1.0 0.0 0:00.38 cpulimit
5633 root 9 -11 76260 372 236 S 1.0 0.0 0:00.39 cpulimit
5651 root 9 -11 76260 308 172 S 1.0 0.0 0:00.30 cpulimit
5653 root 9 -11 76260 136 0 S 1.0 0.0 0:00.25 cpulimit
5670 root 9 -11 76260 136 0 S 1.0 0.0 0:00.16 cpulimit
5671 root 9 -11 76260 136 0 S 1.0 0.0 0:00.14 cpulimit
479 debian-+ 20 0 1327148 59372 0 S 0.6 5.9 50:16.51 obfs4proxy
5330 root 9 -11 76260 392 256 R 0.6 0.0 0:01.69 cpulimit
5333 root 9 -11 76260 392 256 R 0.6 0.0 0:01.75 cpulimit
5344 root 9 -11 76260 128 0 S 0.6 0.0 0:01.70 cpulimit

4

Hey SirNeo, did you fix the problem? If not I have a few ideas:

  • Setting RelayBandwidthRate and RelayBandwidthBurst in the torrc file might reduce the CPU load in a more indirect and “natural” way by limiting how many clients are connected.

  • About using cpulimit, maybe dropping the -m flag could prevent it from launching too many processes. The man page says

“Warning: It is usually a bad idea to use this flag on a shell script. The commands in the script will each spawn a process which will, in turn, spawn more copies of this program to throttle them, bogging down the system.”

  • Also curious if the -c flag is really needed or if it’s part of the issue. Just using -l 50 to limit CPU usage might simplify things.

  • On my own bridge there are also obfs4proxy processes running (/usr/bin/obfs4proxy) that might be worth watching out for too.

Hope that helps!