Hi Stefano, On Fri, Nov 16, 2018 at 05:13:59PM +0100, Stefano Garzarella wrote: > Hi, > I'm investigating the SeaBIOS booting time, to understand if we can reduce > the boot time in some cases (e.g. legacy hardware is not needed). I think > this > can be interesting also for NEMU developers. Definitely, thanks.
> Following this thread ( > https://mail.coreboot.org/pipermail/seabios/2015-July/009497.html), > I'm using qboot (https://github.com/bonzini/qboot) to compare the SeaBIOS > booting time. > > As Paolo did in qboot, I manually add small debug port writes in SeaBIOS and > linuxboot_dma.c (QEMU) to trace the events with perf (kvm_pio events) When doing similar measuremnts, I also used the debug-exit qemu device in order to make imho simpler measuremnts, see https://github.com/intel/nemu/wiki/Measuring-Boot-Latency Probably not as precised as yours, but it was enough for what we tried to characterize. > The goal is to have only one image of SeaBIOS configurable at runtime to > reduce > the boot time, avoiding unnecessary initialization. > > Any pointers or suggestions would be helpful. > > Following I put some preliminary measurements that I obtained: > I used this QEMU command line: > ./qemu-system-x86_64 -bios $BIOS -m 1G -cpu host -M accel=kvm \ > -kernel /boot/vmlinuz-4.18.18-300.fc29.x86_64 -append 'console=ttyS0' \ > -nographic -serial mon:stdio > > For each test, I measured these times (in milliseconds) relative to the > "sched_process_exec" event: > - qemu_init_end: first kvm_entry (i.e. QEMU initialized has finished) > - fw_start: first entry of the BIOS > - fw_do_boot: after the BIOS initialization (e.g. PCI setup, etc.) > - linux_start_boot: before the jump to the Linux kernel Are you planning to also measure the total time to userspace as well? How we set the hardware up from the FW/BIOS can also influence the overall (up to ring 3) boot latency on our experiments. > # qboot > BIOS=/home/stefano/repos/qboot/bios.bin > qemu_init_end: 40.561234 > fw_start: 40.721729 (+0.160495) > fw_do_boot: 47.025591 (+6.303862) > linux_start_boot: 48.874112 (+1.848521) > > # SeaBIOS with default configuration > BIOS=/home/stefano/repos/seabios/out_default/bios.bin > qemu_init_end: 40.419451 > fw_start: 40.639967 (+0.220516) > fw_do_boot: 886.668828 (+846.028861) > linux_start_boot: 889.723547 (+3.054719) > > # SeaBIOS with Kevin's configuration > # (https://mail.coreboot.org/pipermail/seabios/2015-July/009508.html) > # Note: this SeaBIOS setup is so stripped down that it can't actually boot > an OS > BIOS=/home/stefano/repos/seabios/out_kevin/bios.bin > qemu_init_end: 40.676412 > fw_start: 40.755757 (+0.079345) > fw_do_boot: 56.427023 (+15.671266) That's a slight improvement ;) > I did the same tests also with NEMU (without using -M virt) and I have > approximately the same results. Yes, as expected. > As the next step, I'll start from Kevin's configuration to have a minimal > SeaBIOS image ables to boot a Linux kernel. Please keep us posted. Cheers, Samuel.