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Bug
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Resolution: Unresolved
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None
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1.15.2, 20w28a, 1.16.2, 1.16.3, 1.16.4 Pre-release 1
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None
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Guest: Ubuntu 18.04 (Kernel 4.15.0-99)
Hypervisor: KVM Centos 8 (Kernel 4.18.0-147.3.1.el8_1.x86_64)
CPU: Intel(R) Xeon(R) CPU E5-1650 v3 @ 3.50GHz (Haswell)
openjdk version "11.0.7" 2020-04-14
OpenJDK Runtime Environment (build 11.0.7+10-post-Ubuntu-2ubuntu218.04)
OpenJDK 64-Bit Server VM (build 11.0.7+10-post-Ubuntu-2ubuntu218.04, mixed mode, sharing)
Vanilla Minecraft server, version 1.15.2Guest: Ubuntu 18.04 (Kernel 4.15.0-99) Hypervisor: KVM Centos 8 (Kernel 4.18.0-147.3.1.el8_1.x86_64) CPU: Intel(R) Xeon(R) CPU E5-1650 v3 @ 3.50GHz (Haswell) openjdk version "11.0.7" 2020-04-14 OpenJDK Runtime Environment (build 11.0.7+10-post-Ubuntu-2ubuntu218.04) OpenJDK 64-Bit Server VM (build 11.0.7+10-post-Ubuntu-2ubuntu218.04, mixed mode, sharing) Vanilla Minecraft server, version 1.15.2
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Community Consensus
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Performance
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Important
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Platform
Wanted to host a Minecraft server in a VM for a friend.
I've noticed that the CPU usage on the hypervisor host is really high 100-200%, while the VM is showing pretty low CPU usage.
Running dstat showed that the VM is doing a lot of interrupts and context switching even when the server is completely empty.
Host's top when the Minecraft server is stopped:
Dstat output after starting the server, server is empty and there's not much going on except for the Minecraft Java process on the VM:
On the Hypervisor host, the CPU usage for qemu-kvm skyrocketed:
Let's check thread info from ps:
root@minecraft-igor-vm-1:~# ps -eLl | grep 416 4 S 999 416 1 416 0 81 1 - 1201481 futex_ ? 00:00:00 java 1 S 999 416 1 485 0 81 1 - 1201481 futex_ ? 00:00:03 java 1 S 999 416 1 488 0 81 1 - 1201481 futex_ ? 00:00:01 GC Thread#0 1 S 999 416 1 489 0 81 1 - 1201481 futex_ ? 00:00:00 G1 Main Marker 1 S 999 416 1 490 0 81 1 - 1201481 futex_ ? 00:00:00 G1 Conc#0 1 S 999 416 1 501 0 81 1 - 1201481 futex_ ? 00:00:00 G1 Refine#0 1 S 999 416 1 504 0 81 1 - 1201481 futex_ ? 00:00:00 G1 Young RemSet 1 S 999 416 1 518 0 81 1 - 1201481 futex_ ? 00:00:00 VM Thread 1 S 999 416 1 520 0 81 1 - 1201481 futex_ ? 00:00:00 Reference Handl 1 S 999 416 1 521 0 81 1 - 1201481 futex_ ? 00:00:00 Finalizer 1 S 999 416 1 523 0 81 1 - 1201481 futex_ ? 00:00:00 Signal Dispatch 1 S 999 416 1 524 1 81 1 - 1201481 futex_ ? 00:00:15 C2 CompilerThre 1 S 999 416 1 525 0 81 1 - 1201481 futex_ ? 00:00:03 C1 CompilerThre 1 S 999 416 1 526 0 81 1 - 1201481 futex_ ? 00:00:00 Sweeper thread 1 S 999 416 1 527 0 81 1 - 1201481 futex_ ? 00:00:00 Service Thread 1 R 999 416 1 528 0 81 1 - 1201481 - ? 00:00:00 VM Periodic Tas 1 S 999 416 1 529 0 81 1 - 1201481 futex_ ? 00:00:00 Common-Cleaner 1 S 999 416 1 602 0 81 1 - 1201481 futex_ ? 00:00:01 GC Thread#1 1 S 999 416 1 603 2 81 1 - 1201481 futex_ ? 00:00:25 Server-Worker-1 1 S 999 416 1 604 0 81 1 - 1201481 futex_ ? 00:00:00 G1 Refine#1 1 S 999 416 1 605 0 81 1 - 1201481 futex_ ? 00:00:00 Snooper Timer 1 S 999 416 1 606 0 81 1 - 1201481 futex_ ? 00:00:00 Server Infinisl 1 S 999 416 1 607 6 81 1 - 1201481 futex_ ? 00:00:59 Server thread 1 S 999 416 1 609 0 81 1 - 1201481 futex_ ? 00:00:00 ObjectCleanerTh 1 S 999 416 1 610 0 81 1 - 1201481 ep_pol ? 00:00:00 Netty Server IO 1 S 999 416 1 628 0 81 1 - 1201481 futex_ ? 00:00:00 chunk IO worker 1 S 999 416 1 629 0 81 1 - 1201481 futex_ ? 00:00:00 poi IO worker 1 S 999 416 1 630 0 81 1 - 1201481 futex_ ? 00:00:00 chunk IO worker 1 S 999 416 1 631 0 81 1 - 1201481 futex_ ? 00:00:00 poi IO worker 1 S 999 416 1 632 0 81 1 - 1201481 futex_ ? 00:00:00 chunk IO worker 1 S 999 416 1 633 0 81 1 - 1201481 futex_ ? 00:00:00 poi IO worker 1 S 999 416 1 634 0 81 1 - 1201481 poll_s ? 00:00:00 RCON Listener # 1 S 999 416 1 635 0 81 1 - 1201481 futex_ ? 00:00:00 Server Watchdog
Let's measure syscall usage on the system:
syscount-perf -d 3 -c
Tracing for 3 seconds...
SYSCALL COUNT
exit_group 1
nanosleep 1
wait4 1
close 2
epoll_wait 3
inotify_add_watch 4
newstat 5
poll 7
getrusage 10
ioctl 632
sched_yield 18531
futex 37244
Let's double check if our minecraft server is to blame:
syscount-perf -c -p 416 Tracing PID 416... SYSCALL COUNT epoll_wait 3 poll 5 getrusage 10 sched_yield 14747 futex 29638
Let's get a look into strace from 607:
futex(0x7f8c08feabd8, FUTEX_WAIT_PRIVATE, 0, {tv_sec=0, tv_nsec=99535}) = -1 ETIMEDOUT (Connection timed out)
futex(0x7f8c08feab88, FUTEX_WAKE_PRIVATE, 1) = 0
sched_yield() = 0
futex(0x7f8c08feabd8, FUTEX_WAIT_PRIVATE, 0, {tv_sec=0, tv_nsec=99533}) = -1 ETIMEDOUT (Connection timed out)
futex(0x7f8c08feab88, FUTEX_WAKE_PRIVATE, 1) = 0
sched_yield() = 0
futex(0x7f8c08feabd8, FUTEX_WAIT_PRIVATE, 0, {tv_sec=0, tv_nsec=99491}) = -1 ETIMEDOUT (Connection timed out)
futex(0x7f8c08feab88, FUTEX_WAKE_PRIVATE, 1) = 0
sched_yield() = 0
futex(0x7f8c08feabd8, FUTEX_WAIT_PRIVATE, 0, {tv_sec=0, tv_nsec=99442}) = -1 ETIMEDOUT (Connection timed out)
futex(0x7f8c08feab88, FUTEX_WAKE_PRIVATE, 1) = 0
sched_yield() = 0
futex(0x7f8c08feabd8, FUTEX_WAIT_PRIVATE, 0, {tv_sec=0, tv_nsec=99500}) = -1 ETIMEDOUT (Connection timed out)
futex(0x7f8c08feab88, FUTEX_WAKE_PRIVATE, 1) = 0
sched_yield() = 0
futex(0x7f8c08feabd8, FUTEX_WAIT_PRIVATE, 0, {tv_sec=0, tv_nsec=99484}) = -1 ETIMEDOUT (Connection timed out)
futex(0x7f8c08feab88, FUTEX_WAKE_PRIVATE, 1) = 0
sched_yield() = 0
futex(0x7f8c08feabd8, FUTEX_WAIT_PRIVATE, 0, {tv_sec=0, tv_nsec=99474}) = -1 ETIMEDOUT (Connection timed out)
futex(0x7f8c08feab88, FUTEX_WAKE_PRIVATE, 1) = 0
sched_yield() = 0
futex(0x7f8c08feabd8, FUTEX_WAIT_PRIVATE, 0, {tv_sec=0, tv_nsec=99545}) = -1 ETIMEDOUT (Connection timed out)
futex(0x7f8c08feab88, FUTEX_WAKE_PRIVATE, 1) = 0
sched_yield() = 0
futex(0x7f8c08feabd8, FUTEX_WAIT_PRIVATE, 0, {tv_sec=0, tv_nsec=99520}) = -1 ETIMEDOUT (Connection timed out)
futex(0x7f8c08feab88, FUTEX_WAKE_PRIVATE, 1) = 0
sched_yield() = 0
futex(0x7f8c08feabd8, FUTEX_WAIT_PRIVATE, 0, {tv_sec=0, tv_nsec=99291}) = -1 ETIMEDOUT (Connection timed out)
futex(0x7f8c08feab88, FUTEX_WAKE_PRIVATE, 1) = 0
sched_yield() = 0
futex(0x7f8c08feabd8, FUTEX_WAIT_PRIVATE, 0, {tv_sec=0, tv_nsec=99496}) = -1 ETIMEDOUT (Connection timed out)
futex(0x7f8c08feab88, FUTEX_WAKE_PRIVATE, 1) = 0
sched_yield() = 0
futex(0x7f8c08feabd8, FUTEX_WAIT_PRIVATE, 0, {tv_sec=0, tv_nsec=99542}) = -1 ETIMEDOUT (Connection timed out)
futex(0x7f8c08feab88, FUTEX_WAKE_PRIVATE, 1) = 0
sched_yield() = 0
futex(0x7f8c08feabd8, FUTEX_WAIT_PRIVATE, 0, {tv_sec=0, tv_nsec=99450}) = -1 ETIMEDOUT (Connection timed out)
futex(0x7f8c08feab88, FUTEX_WAKE_PRIVATE, 1) = 0
sched_yield() = 0
futex(0x7f8c08feabd8, FUTEX_WAIT_PRIVATE, 0, {tv_sec=0, tv_nsec=99507}) = -1 ETIMEDOUT (Connection timed out)
futex(0x7f8c08feab88, FUTEX_WAKE_PRIVATE, 1) = 0
sched_yield() = 0
futex(0x7f8c08feabd8, FUTEX_WAIT_PRIVATE, 0, {tv_sec=0, tv_nsec=99489}) = -1 ETIMEDOUT (Connection timed out)
futex(0x7f8c08feab88, FUTEX_WAKE_PRIVATE, 1) = 0
sched_yield() = 0
futex(0x7f8c08feabd8, FUTEX_WAIT_PRIVATE, 0, {tv_sec=0, tv_nsec=99460}) = -1 ETIMEDOUT (Connection timed out)
futex(0x7f8c08feab88, FUTEX_WAKE_PRIVATE, 1) = 0
sched_yield() = 0
futex(0x7f8c08feabd8, FUTEX_WAIT_PRIVATE, 0, {tv_sec=0, tv_nsec=99454}) = -1 ETIMEDOUT (Connection timed out)
futex(0x7f8c08feab88, FUTEX_WAKE_PRIVATE, 1) = 0
sched_yield() = 0
futex(0x7f8c08feabd8, FUTEX_WAIT_PRIVATE, 0, {tv_sec=0, tv_nsec=99442}) = -1 ETIMEDOUT (Connection timed out)
futex(0x7f8c08feab88, FUTEX_WAKE_PRIVATE, 1) = 0
sched_yield() = 0
futex(0x7f8c08feabd8, FUTEX_WAIT_PRIVATE, 0, {tv_sec=0, tv_nsec=99500}) = -1 ETIMEDOUT (Connection timed out)
futex(0x7f8c08feab88, FUTEX_WAKE_PRIVATE, 1) = 0
sched_yield() = 0
futex(0x7f8c08feabd8, FUTEX_WAIT_PRIVATE, 0, {tv_sec=0, tv_nsec=99449}) = -1 ETIMEDOUT (Connection timed out)
futex(0x7f8c08feab88, FUTEX_WAKE_PRIVATE, 1) = 0
sched_yield() = 0
futex(0x7f8c08feabd8, FUTEX_WAIT_PRIVATE, 0, {tv_sec=0, tv_nsec=99453}) = -1 ETIMEDOUT (Connection timed out)
futex(0x7f8c08feab88, FUTEX_WAKE_PRIVATE, 1) = 0
sched_yield() = 0
futex(0x7f8c08feabd8, FUTEX_WAIT_PRIVATE, 0, {tv_sec=0, tv_nsec=99488}) = -1 ETIMEDOUT (Connection timed out)
futex(0x7f8c08feab88, FUTEX_WAKE_PRIVATE, 1) = 0
sched_yield() = 0
futex(0x7f8c08feabd8, FUTEX_WAIT_PRIVATE, 0, {tv_sec=0, tv_nsec=99481}) = -1 ETIMEDOUT (Connection timed out)
futex(0x7f8c08feab88, FUTEX_WAKE_PRIVATE, 1) = 0
sched_yield() = 0
futex(0x7f8c08feabd8, FUTEX_WAIT_PRIVATE, 0, {tv_sec=0, tv_nsec=99520}) = -1 ETIMEDOUT (Connection timed out)
futex(0x7f8c08feab88, FUTEX_WAKE_PRIVATE, 1) = 0
sched_yield() = 0
futex(0x7f8c08feabd8, FUTEX_WAIT_PRIVATE, 0, {tv_sec=0, tv_nsec=99461}) = -1 ETIMEDOUT (Connection timed out)
futex(0x7f8c08feab88, FUTEX_WAKE_PRIVATE, 1) = 0
sched_yield() = 0
futex(0x7f8c08feabd8, FUTEX_WAIT_PRIVATE, 0, {tv_sec=0, tv_nsec=99577}) = -1 ETIMEDOUT (Connection timed out)
futex(0x7f8c08feab88, FUTEX_WAKE_PRIVATE, 1) = 0
sched_yield() = 0
futex(0x7f8c08feabd8, FUTEX_WAIT_PRIVATE, 0, {tv_sec=0, tv_nsec=99527}) = -1 ETIMEDOUT (Connection timed out)
futex(0x7f8c08feab88, FUTEX_WAKE_PRIVATE, 1) = 0
sched_yield() = 0
futex(0x7f8c08feabd8, FUTEX_WAIT_PRIVATE, 0, {tv_sec=0, tv_nsec=99512}) = -1 ETIMEDOUT (Connection timed out)
futex(0x7f8c08feab88, FUTEX_WAKE_PRIVATE, 1) = 0
sched_yield() = 0
futex(0x7f8c08feabd8, FUTEX_WAIT_PRIVATE, 0, {tv_sec=0, tv_nsec=99462}) = -1 ETIMEDOUT (Connection timed out)
futex(0x7f8c08feab88, FUTEX_WAKE_PRIVATE, 1) = 0
sched_yield() = 0
futex(0x7f8c08feabd8, FUTEX_WAIT_PRIVATE, 0, {tv_sec=0, tv_nsec=99449}) = -1 ETIMEDOUT (Connection timed out)
futex(0x7f8c08feab88, FUTEX_WAKE_PRIVATE, 1) = 0
sched_yield() = 0
futex(0x7f8c08feabd8, FUTEX_WAIT_PRIVATE, 0, {tv_sec=0, tv_nsec=99468}) = -1 ETIMEDOUT (Connection timed out)
futex(0x7f8c08feab88, FUTEX_WAKE_PRIVATE, 1) = 0
sched_yield() = 0
Now let's try Minecraft Server 1.13.2:
CPU usage on host is low:
No excessive context switching or interrupts on guest:
Threads:
4 S 999 841 1 841 0 81 1 - 1255053 futex_ ? 00:00:00 java 1 S 999 841 1 842 1 81 1 - 1255053 futex_ ? 00:00:03 java 1 S 999 841 1 843 0 81 1 - 1255053 futex_ ? 00:00:00 GC Thread#0 1 S 999 841 1 844 0 81 1 - 1255053 futex_ ? 00:00:00 G1 Main Marker 1 S 999 841 1 845 0 81 1 - 1255053 futex_ ? 00:00:00 G1 Conc#0 1 S 999 841 1 846 0 81 1 - 1255053 futex_ ? 00:00:00 G1 Refine#0 1 S 999 841 1 847 0 81 1 - 1255053 futex_ ? 00:00:00 G1 Young RemSet 1 S 999 841 1 848 0 81 1 - 1255053 futex_ ? 00:00:00 VM Thread 1 S 999 841 1 849 0 81 1 - 1255053 futex_ ? 00:00:00 Reference Handl 1 S 999 841 1 850 0 81 1 - 1255053 futex_ ? 00:00:00 Finalizer 1 S 999 841 1 851 0 81 1 - 1255053 futex_ ? 00:00:00 Signal Dispatch 1 S 999 841 1 852 12 81 1 - 1255053 futex_ ? 00:00:25 C2 CompilerThre 1 S 999 841 1 853 1 81 1 - 1255053 futex_ ? 00:00:02 C1 CompilerThre 1 S 999 841 1 854 0 81 1 - 1255053 futex_ ? 00:00:00 Sweeper thread 1 S 999 841 1 855 0 81 1 - 1255053 futex_ ? 00:00:00 Service Thread 1 S 999 841 1 856 0 81 1 - 1255053 futex_ ? 00:00:00 VM Periodic Tas 1 S 999 841 1 857 0 81 1 - 1255053 futex_ ? 00:00:00 Common-Cleaner 1 S 999 841 1 859 0 81 1 - 1255053 futex_ ? 00:00:00 GC Thread#1 1 S 999 841 1 860 0 81 1 - 1255053 futex_ ? 00:00:00 G1 Refine#1 1 S 999 841 1 2369 0 81 1 - 1255053 futex_ ? 00:00:00 Snooper Timer 1 S 999 841 1 2370 0 81 1 - 1255053 futex_ ? 00:00:00 Server Infinisl 1 S 999 841 1 2371 5 81 1 - 1255053 futex_ ? 00:00:09 Server thread 1 S 999 841 1 2373 0 81 1 - 1255053 futex_ ? 00:00:00 ObjectCleanerTh 1 S 999 841 1 2374 0 81 1 - 1255053 ep_pol ? 00:00:00 Netty Server IO 1 S 999 841 1 2375 0 81 1 - 1255053 futex_ ? 00:00:00 WorldGen-Schedu 1 S 999 841 1 2376 7 81 1 - 1255053 futex_ ? 00:00:13 WorldGen-Worker 1 S 999 841 1 2377 0 81 1 - 1255053 poll_s ? 00:00:00 RCON Listener # 1 S 999 841 1 2378 0 81 1 - 1255053 futex_ ? 00:00:00 Server Watchdog 1 S 999 841 1 2379 0 81 1 - 1255053 futex_ ? 00:00:01 File IO Thread
Now let's check syscall count:
syscount-perf -d 3 -c
Tracing for 3 seconds...
SYSCALL COUNT
exit_group 1
wait4 1
close 2
epoll_wait 3
poll 6
getrusage 10
ioctl 632
futex 5726
This issue seems to be connected with: MC-149018
Maybe some multithreading changes or something messed up the performance for VMs?
It looks like it all started in 1.14.
Let me know if there's anything more I can add to the report to help you with resolving this.
