Re: [Qemu-devel] [PATCH] qemu:cpuid: speedup test by 3x times if grub2 is available

[Eduardo Habkost]

On Thu, Feb 14, 2013 at 08:28:03PM +0100, Igor Mammedov wrote:
> On Thu, 14 Feb 2013 13:13:18 +0100
> Paolo Bonzini <address@hidden> wrote:
> 
> > Il 14/02/2013 12:18, Eduardo Habkost ha scritto:
> > >> > qemu boots from disk image 3 times faster than direct kernel load.
> > > That's surprising. Do you have any idea why that happens?
> > 
> > Because kernel load uses MMIO (from fw_cfg), while booting from disk
> > uses at worst PCI DMA and at best virtio.
> > 
> > Paolo
> I've tried Paolo's suggestion to run in TCG mode with instruction logging,
> and it spends too much time reading 11K kernel from qemu compared to
> kvm-unit-test kernel. I'll need debug it further to find out why.
> But this patch looks unnecessary if I could fix qemu/seabios or test kernel
> to reach the same load time as kvm-unit-test kernel.

Agreed.

Lucas, please don't apply this patch yet, until we find the actual cause
of the slow booting.

-- 
Eduardo