[Qemu-devel] QEMU/NEMU boot time with several x86 firmwares

[Stefano Garzarella]

Hi Samuel, Rob,
I'm proceeding to compare several x86 firmwares in order to understand
which suits better with -kernel option to have a fast boot with
QEMU/NEMU.

For your use cases, what boot time do you expect?


I compared SeaBIOS, qboot, and OVMF. I started each test using this
qemu parameters: "./qemu-system-x86_64 -bios path/to/bios.bin -m 1G
-cpu host -M accel=kvm -vga none -kernel path/to/bzImage -initrd
path/to/rootfs.cpio ..."

As Samuel suggested, I added the total time to userspace adding a
probe in the kernel_init(), so the times (in msec) that I measured
are:
- qemu_init_end: first kvm_entry (i.e. QEMU initialized has finished)
- fw_start: first entry of the firmware
- fw_do_boot: after the firmware initialization (e.g. PCI setup, etc.)
- linux_start_boot: before the jump to the Linux kernel
- linux_start_user: before starting the init process

* SeaBIOS
Default configuration without debug messages (CONFIG_DEBUG_LEVEL=0) +
Stephen's patch (tpm: Check for TPM related ACPI tables before
attempting hw) + my patch (qemu: fast boot when linuxboot optionrom is
used).
 qemu_init_end: 41.634812
 fw_start: 41.857374 (+0.222562)
 fw_do_boot: 52.754109 (+10.896735)
 linux_start_boot: 54.117220 (+1.363111)
 linux_start_user: 495.684199 (+441.566979)

* qboot
Default configuration + my patch (pci: reduce pci_foreach() calls).
 qemu_init_end: 40.233717
 fw_start: 40.384048 (+0.150331)
 fw_do_boot: 45.660497 (+5.276449)
 linux_start_boot: 47.252119 (+1.591622)
 linux_start_user: 509.173886 (+461.921767)

* OVMF (https://github.com/intel/ovmf-virt)
I followed this script
(https://github.com/intel/nemu/blob/topic/virt-x86/tools/CI/run_nats.sh)
to build OVMF.
Note: I put the "fw_start" probe in the BdsEntry()
[MdeModulePkg/Universal/BdsDxe/BdsEntry.c], I'm not sure if it is
"near" to the real entry point.
 qemu_init_end: 42.734555
 fw_start: 163.611506 (+120.876951)
 fw_do_boot: 369.713760 (+206.102254)
 linux_start_boot: 370.960364 (+1.246604)
 linux_start_user: 796.799667 (+425.839303)

For OVMF case, are reasonable the times that I measured? Do you use a
different configuration?

Thanks,
Stefano

-- 
Stefano Garzarella
Red Hat