[SeaBIOS] [Qemu-devel] Hack integrating SeaBios / LinuxBoot option rom with QEMU trace backends

Kevin O'Connor kevin at koconnor.net
Tue Oct 11 01:57:53 CEST 2011

On Mon, Oct 10, 2011 at 06:08:03PM +0100, Daniel P. Berrange wrote:
> I've been investigating where time disappears to when booting Linux guests.
> Initially I enabled DEBUG_BIOS in QEMU's hw/pc.c, and then hacked it so
> that it could print a timestamp before each new line of debug output. The
> problem with that is that it slowed down startup, so the timings I was
> examining all changed.

A lot of effort went into optimizing SeaBIOS boot time.  There is a
tool in seabios git to help with benchmarking - tools/readserial.py.
The tool was designed for use with serial ports on real machines using
coreboot, but it works with qemu too:

mkfifo seabioslog

./tools/readserial.py -nf seabioslog

qemu-system-x86_64 -chardev pipe,id=seabios,path=seabioslog -device isa-debugcon,iobase=0x402,chardev=seabios -hda myimage

This will show the SeaBIOS debug output with timing info.


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