[Qemu-devel] Why qemu log start late and qemu start guest so long while using '-mem-prealloc' option?

[Sam]

Hi all,

I'm using qemu to start vm in huge page enviroment, I use CMD1 and CMD2 to
test the time of start of a vm, CMD1 contains option '-mem-prealloc', CMD2
does not contain this.

I found while using CMD1, the time to run this command is longer then CMD2.
For words, I know this option is to wait memory ready, but for code, I
don't know where is the different with CMD1 and CMD2.

As I print log of CMD1 and CMD2, I found for CMD1, there are about 10
second to print first log. I don't know for '-mem-prealloc' option, what
qemu wait for? thank you~


detail of test:

CMD1="$QEMU_CMD -D qemu.log -trace events=qemu-events-all -enable-kvm -cpu
qemu64,+vmx,+ssse3,+sse4.1,+sse4.2,+x2apic,+aes,+avx,+vme,+pat,+ss,+pclmulqdq,+xsave,level=13
-machine pc,accel=kvm -chardev
socket,id=hmqmondev,port=55908,host=127.0.0.1,nodelay,server,nowait -mon
chardev=hmqmondev,id=hmqmon,mode=readline -rtc
base=utc,clock=host,driftfix=none -usb -device usb-tablet -daemonize
-nodefaults -nodefconfig -no-kvm-pit-reinjection -global
kvm-pit.lost_tick_policy=discard -vga std -k en-us -smp 8 -name
gangyewei-qemutime-1 -m 40960 -boot order=cdn -vnc :8,password -drive
file=$DISK_0,if=none,id=drive_0,format=qcow2,cache=none,aio=native -device
virtio-blk-pci,id=dev_drive_0,drive=drive_0,bus=pci.0,addr=0x5 -drive
file=$DISK_1,if=none,id=drive_1,format=qcow2,cache=none,aio=native -device
virtio-blk-pci,id=dev_drive_1,drive=drive_1,bus=pci.0,addr=0x6 -drive
file=$DISK_2,if=none,id=drive_2,format=qcow2,cache=none,aio=native -device
virtio-blk-pci,id=dev_drive_2,drive=drive_2,bus=pci.0,addr=0x7 -device
ide-cd,drive=ide0-cd0,bus=ide.1,unit=1 -drive
id=ide0-cd0,media=cdrom,if=none -chardev
socket,id=char-n-52b49b80,path=/usr/local/var/run/openvswitch/n-52b49b80,server
-netdev type=vhost-user,id=n-52b49b80,chardev=char-n-52b49b80,vhostforce=on
-device
virtio-net-pci,netdev=n-52b49b80,mac=00:22:52:b4:9b:80,id=netdev-n-52b49b80,addr=0xf$(nic_speed
10000) -object
memory-backend-file,id=mem,size=40960M,mem-path=/mnt/huge,share=on -numa
node,memdev=mem -pidfile $PID_FILE -chardev
socket,path=/opt/cloud/workspace/servers/4511f52a-f450-40d3-9417-a1e0a27ed507/qga.sock,server,nowait,id=qga0
-device virtio-serial -device
virtserialport,chardev=qga0,name=org.qemu.guest_agent.0"

CMD2="$QEMU_CMD -D qemu.log -trace events=qemu-events-all -enable-kvm -cpu
qemu64,+vmx,+ssse3,+sse4.1,+sse4.2,+x2apic,+aes,+avx,+vme,+pat,+ss,+pclmulqdq,+xsave,level=13
-machine pc,accel=kvm -chardev
socket,id=hmqmondev,port=55908,host=127.0.0.1,nodelay,server,nowait -mon
chardev=hmqmondev,id=hmqmon,mode=readline -rtc
base=utc,clock=host,driftfix=none -usb -device usb-tablet -daemonize
-nodefaults -nodefconfig -no-kvm-pit-reinjection -global
kvm-pit.lost_tick_policy=discard -vga std -k en-us -smp 8 -name
gangyewei-qemutime-1 -m 40960 -boot order=cdn -vnc :8,password -drive
file=$DISK_0,if=none,id=drive_0,format=qcow2,cache=none,aio=native -device
virtio-blk-pci,id=dev_drive_0,drive=drive_0,bus=pci.0,addr=0x5 -drive
file=$DISK_1,if=none,id=drive_1,format=qcow2,cache=none,aio=native -device
virtio-blk-pci,id=dev_drive_1,drive=drive_1,bus=pci.0,addr=0x6 -drive
file=$DISK_2,if=none,id=drive_2,format=qcow2,cache=none,aio=native -device
virtio-blk-pci,id=dev_drive_2,drive=drive_2,bus=pci.0,addr=0x7 -device
ide-cd,drive=ide0-cd0,bus=ide.1,unit=1 -drive
id=ide0-cd0,media=cdrom,if=none -chardev
socket,id=char-n-52b49b80,path=/usr/local/var/run/openvswitch/n-52b49b80,server
-netdev type=vhost-user,id=n-52b49b80,chardev=char-n-52b49b80,vhostforce=on
-device
virtio-net-pci,netdev=n-52b49b80,mac=00:22:52:b4:9b:80,id=netdev-n-52b49b80,addr=0xf$(nic_speed
10000) -object
memory-backend-file,id=mem,size=40960M,mem-path=/mnt/huge,share=on -numa
node,memdev=mem -mem-prealloc -pidfile $PID_FILE -chardev
socket,path=/opt/cloud/workspace/servers/4511f52a-f450-40d3-9417-a1e0a27ed507/qga.sock,server,nowait,id=qga0
-device virtio-serial -device
virtserialport,chardev=qga0,name=org.qemu.guest_agent.0"


time to run CMD1:
address@hidden 4511f52a-f450-40d3-9417-a1e0a27ed507]# sh startvm
ls: cannot access
/opt/cloud/workspace/servers/4511f52a-f450-40d3-9417-a1e0a27ed507/STATEFILE*:
No such file or directory
Wed Oct 25 16:52:51 CST 2017  (unix time is 1508921571)
qemu-system-x86_64_2.6.0:qemu-events-all:1045: WARNING: trace event
'qxl_interface_set_mm_time' is not traceable
qemu-system-x86_64_2.6.0:qemu-events-all:1046: WARNING: trace event
'qxl_io_write_vga' is not traceable
qemu-system-x86_64_2.6.0:qemu-events-all:1318: WARNING: trace event
'exec_tb' is not traceable
qemu-system-x86_64_2.6.0:qemu-events-all:1319: WARNING: trace event
'exec_tb_nocache' is not traceable
qemu-system-x86_64_2.6.0:qemu-events-all:1320: WARNING: trace event
'exec_tb_exit' is not traceable
qemu-system-x86_64_2.6.0: -no-kvm-pit-reinjection: warning: deprecated,
replaced by -global kvm-pit.lost_tick_policy=discard
Wed Oct 25 16:53:02 CST 2017  (unix time is 1508921582)
qemu started

first log of CMD1:
address@hidden:qio_channel_socket_new Socket new ioc=0x55555640efd0
I don't know why first log happends in 1508921581, not the start up time,
which is 1508921571.


time to run CMD2:
address@hidden 4511f52a-f450-40d3-9417-a1e0a27ed507]# sh startvm
ls: cannot access
/opt/cloud/workspace/servers/4511f52a-f450-40d3-9417-a1e0a27ed507/STATEFILE*:
No such file or directory
Wed Oct 25 18:15:35 CST 2017
qemu-system-x86_64_2.6.0:qemu-events-all:1045: WARNING: trace event
'qxl_interface_set_mm_time' is not traceable
qemu-system-x86_64_2.6.0:qemu-events-all:1046: WARNING: trace event
'qxl_io_write_vga' is not traceable
qemu-system-x86_64_2.6.0:qemu-events-all:1318: WARNING: trace event
'exec_tb' is not traceable
qemu-system-x86_64_2.6.0:qemu-events-all:1319: WARNING: trace event
'exec_tb_nocache' is not traceable
qemu-system-x86_64_2.6.0:qemu-events-all:1320: WARNING: trace event
'exec_tb_exit' is not traceable
qemu-system-x86_64_2.6.0: -no-kvm-pit-reinjection: warning: deprecated,
replaced by -global kvm-pit.lost_tick_policy=discard
Wed Oct 25 18:15:36 CST 2017
qemu started

first log of CMD1:
address@hidden:qio_channel_socket_new Socket new ioc=0x55555640efd0