Re: [Qemu-devel] Why is SeaBIOS used with -kernel?

[Richard W.M. Jones]

On Fri, Apr 01, 2016 at 01:32:51PM +0200, Gerd Hoffmann wrote:
>   Hi,
> 
> > I think we were working on the same thing ...  Attached is my
> > version.
> > 
> > Note that you must enable at least CONFIG_MPTABLE else virtio-scsi
> > does not work in the guest.  I also enabled ACPI & SMBIOS & PIRTABLE.
> 
> They are enabled by default, no need to explicitly say so ;)

So they are.  Here's a v3 patch.

I also retested everything from scratch.  Previously I was testing the
stock SeaBIOS bios.bin shipped with qemu vs the fast config.  However
that has the possible problem that I was testing two slightly
different versions of SeaBIOS (whatever version qemu ships vs
upstream).

Testing from scratch, using upstream SeaBIOS in both cases, there's
still a significant benefit.  SeaBIOS overhead goes from 63 ms down to
19 ms (saving 44 ms).

Overall the proportion of boot time of the libguestfs appliance
attributed to SeaBIOS drops from 3.7% to 1.1% (but note this is with
libguestfs & kernel debugging enabled -- for real users there'd be a
much larger percentage drop).

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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0001-bios-Add-fast-variant-of-SeaBIOS-for-use-with-kernel.patch
Description: Text document