tests/vm/openbsd script (etc) excessive CPU usage

tests/vm/openbsd script (etc) excessive CPU usage

[Peter Maydell]

I noticed that when running the BSD VMs, the Python script that launches
QEMU seems to eat CPU:

peter.m+ 19024  0.0  0.0  20296 11692 pts/12   S+   15:04   0:00
   \_ make -C build vm-build-openbsd J=8 V=1
peter.m+ 19858 98.8  0.0 126272 15220 pts/12   Sl+  15:04  12:04
       \_ /usr/bin/python3 -B
/home/peter.maydell/qemu-openbsd/tests/vm/openbsd --debug --jobs 8
--verbose --efi-aarch64
/home/peter.maydell/qemu-openbsd/build/pc-bios/edk2-aarch64-code.fd
--image /home/peter.maydell/.cache/qemu-vm/images/openbsd.img
--snapshot --build-qemu /home/peter.maydell/qemu-openbsd --
peter.m+ 22878  711  3.2 10506236 3192896 pts/12 Sl+ 15:04  86:08
            \_ qemu-system-x86_64 -display none -vga none -chardev
socket,id=mon,path=/var/tmp/qemu-19858-monitor.sock -mon
chardev=mon,mode=control -machine pc -chardev
socket,id=console,path=/var/tmp/qemu-19858-console.sock,server,nowait
-serial chardev:console -nodefaults -m 4G -cpu max -netdev
user,id=vnet,hostfwd=:127.0.0.1:0-:22 -device
virtio-net-pci,netdev=vnet -vnc 127.0.0.1:0,to=20 -smp 8 -enable-kvm
-drive file=/home/peter.maydell/.cache/qemu-vm/images/openbsd.img,snapshot=on,if=none,id=drive0,cache=writeback
-device virtio-blk,drive=drive0,bootindex=0 -drive
file=/home/peter.maydell/qemu-openbsd/build/vm-test-g6q_po6_.tmp/data-993a1.tar,if=none,id=data-993a1,cache=writeback,format=raw
-device virtio-blk,drive=data-993a1,serial=data-993a1,bootindex=1
peter.m+ 29304  0.0  0.0  63612  4996 pts/12   S+   15:05   0:00
           \_ ssh -t -o StrictHostKeyChecking=no -o
UserKnownHostsFile=/dev/null -o ConnectTimeout=1 -p 38491 -i
/home/peter.maydell/qemu-openbsd/build/vm-test-g6q_po6_.tmp/id_rsa -o
SendEnv=https_proxy -o SendEnv=http_proxy -o SendEnv=ftp_proxy -o
SendEnv=no_proxy qemu@127.0.0.1          set -e;         rm -rf
/home/qemu/qemu-test.*         cd $(mktemp -d
/home/qemu/qemu-test.XXXXXX);         mkdir src build; cd src;
tar -xf /dev/rsd1c;         cd ../build         ../src/configure
--cc=cc --python=python3 ;


Notice that process 19858 (the python script) is at 98.8% CPU.
This isn't specific to the OpenBSD script, the other BSD scripts
do this too.

Why is this script using so much CPU when it should basically just be
waiting for the QEMU VM to finish ?

I think this is probably a recent regression, though I'm not certain.

thanks
-- PMM

Re: tests/vm/openbsd script (etc) excessive CPU usage

[Alex Bennée]

Peter Maydell <peter.maydell@linaro.org> writes:

> I noticed that when running the BSD VMs, the Python script that launches
> QEMU seems to eat CPU:
>
> peter.m+ 19024  0.0  0.0  20296 11692 pts/12   S+   15:04   0:00
>    \_ make -C build vm-build-openbsd J=8 V=1
> peter.m+ 19858 98.8  0.0 126272 15220 pts/12   Sl+  15:04  12:04
>        \_ /usr/bin/python3 -B
> /home/peter.maydell/qemu-openbsd/tests/vm/openbsd --debug --jobs 8
> --verbose --efi-aarch64
> /home/peter.maydell/qemu-openbsd/build/pc-bios/edk2-aarch64-code.fd
> --image /home/peter.maydell/.cache/qemu-vm/images/openbsd.img
> --snapshot --build-qemu /home/peter.maydell/qemu-openbsd --
> peter.m+ 22878  711  3.2 10506236 3192896 pts/12 Sl+ 15:04  86:08
>             \_ qemu-system-x86_64 -display none -vga none -chardev
> socket,id=mon,path=/var/tmp/qemu-19858-monitor.sock -mon
> chardev=mon,mode=control -machine pc -chardev
> socket,id=console,path=/var/tmp/qemu-19858-console.sock,server,nowait
> -serial chardev:console -nodefaults -m 4G -cpu max -netdev
> user,id=vnet,hostfwd=:127.0.0.1:0-:22 -device
> virtio-net-pci,netdev=vnet -vnc 127.0.0.1:0,to=20 -smp 8 -enable-kvm
> -drive file=/home/peter.maydell/.cache/qemu-vm/images/openbsd.img,snapshot=on,if=none,id=drive0,cache=writeback
> -device virtio-blk,drive=drive0,bootindex=0 -drive
> file=/home/peter.maydell/qemu-openbsd/build/vm-test-g6q_po6_.tmp/data-993a1.tar,if=none,id=data-993a1,cache=writeback,format=raw
> -device virtio-blk,drive=data-993a1,serial=data-993a1,bootindex=1
> peter.m+ 29304  0.0  0.0  63612  4996 pts/12   S+   15:05   0:00
>            \_ ssh -t -o StrictHostKeyChecking=no -o
> UserKnownHostsFile=/dev/null -o ConnectTimeout=1 -p 38491 -i
> /home/peter.maydell/qemu-openbsd/build/vm-test-g6q_po6_.tmp/id_rsa -o
> SendEnv=https_proxy -o SendEnv=http_proxy -o SendEnv=ftp_proxy -o
> SendEnv=no_proxy qemu@127.0.0.1          set -e;         rm -rf
> /home/qemu/qemu-test.*         cd $(mktemp -d
> /home/qemu/qemu-test.XXXXXX);         mkdir src build; cd src;
> tar -xf /dev/rsd1c;         cd ../build         ../src/configure
> --cc=cc --python=python3 ;
>
>
> Notice that process 19858 (the python script) is at 98.8% CPU.
> This isn't specific to the OpenBSD script, the other BSD scripts
> do this too.
>
> Why is this script using so much CPU when it should basically just be
> waiting for the QEMU VM to finish ?
>
> I think this is probably a recent regression, though I'm not certain.

Robert thinks this is fixed up with the latest clean-ups for the console
drain thread which is in today's PR. I've not seen it while testing the
PR so I think it's gone.

-- 
Alex Bennée