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