Unity creates too many threads

Question

We use headless linux build (running in batchmode) for our dedicated servers and we launch multiple application instances on each of our server machines. But we encountered a problem that each process creates too many threads which seem unnecessary. It looks as if number of threads depends on the number of logical cores of the running machine. For example on 1-core VM it creates 30 threads, on 4-core - 37 threads, on 36-core production machine - 99 threads. On my windows machine with 12 cores - 60 threads. So the problem not only for linux builds.

There is another worrying notice, but I'm not sure if it's connected to the threads issue: more than half of CPU time is consumed by system calls and strace shows following results (for a 20 seconds interval):

% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
 99.59    3.971471          38    105655           futex
  0.21    0.008423          23       366           stat
  0.15    0.006040          33       185           sendto
  0.03    0.001224          26        47        47 accept
  0.01    0.000269         269         1           restart_syscall
  0.00    0.000198           8        24        12 write
  0.00    0.000059           5        12           lseek
  0.00    0.000000           0         1           clone
  0.00    0.000000           0         2           uname
------ ----------- ----------- --------- --------- ----------------
100.00    3.987684                106293        59 total

We tried following things:

Disabling development mode
Setting "Realtime Global Illumination CPU usage" in graphics settings to low
Disabling GI for each scene by setting "m_EnableRealtimeLightmaps", "m_EnableBakedLightmaps", "m_AlbedoBoost" to 0 and "m_GIWorkflowMode" to 1 in scene files
Setting CPU affinity to a single core using either taskset utility and sched_setaffinity system call

Nothing seems to have any effect on amount of threads. We use Unity 2018.2.12f1 but we also tried 2018.3.8f1

Is there a way to reduce number of threads unity creates and therefore decrease corresponding overhead?

Answer 1

Answer by LarsGameloft · Nov 02, 2020 at 10:10 PM

Did you get an answer for this? I am having an issue where my app creates more threads than allowed by the hardware. Thank you

Add comment · Share

Unity creates too many threads

1 Reply

Your answer

Follow this Question

Related Questions