io.netty.channel.epoll.Native.epollWait0 Takes up most of the CPU

[shiyiyue1102]

I send 15000 tps from clients in my loader testing,then I found my server's cpu up to 95%

top:

jstack info for the top threads :

grpc-java version is : 1.24.0 （grpc-netty shaded ）

is it normal that this native method take up most of the cpu?

[ejona86]

Those stack traces show epollWait. That's the stack trace of an idle thread. That stack trace does not generate any CPU utilization until an event comes and returns from the kernel. So it is appropriate that many threads are sitting there not contributing toward CPU usage.

[sanjaypujare]

This Stackoverflow post discusses something similar. Please read the comments at the bottom.

[shiyiyue1102]

Those stack traces show epollWait. That's the stack trace of an idle thread. That stack trace does not generate any CPU utilization until an event comes and returns from the kernel. So it is appropriate that many threads are sitting there not contributing toward CPU usage.

You mean that epoolWait is not a CPU-consuming operation, but other operations that not showed in the stacktrace in the same thread？

[ejona86]

I'm saying the stack traces you showed showed no CPU usage. Either other threads are using CPU or you missed the point where those threads were using CPU.

[shiyiyue1102]

I'm saying the stack traces you showed showed no CPU usage. Either other threads are using CPU or you missed the point where those threads were using CPU.

Thank ,I have found the actual cpu usage via Arthas profiler .