From: Anthony Liguori <anthony@codemonkey.ws>
To: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] vga slow with -enable-kvm
Date: Fri, 07 Nov 2008 08:02:09 -0600 [thread overview]
Message-ID: <49144A61.9030708@codemonkey.ws> (raw)
In-Reply-To: <491407E9.4040506@redhat.com>
Gerd Hoffmann wrote:
> Hi,
>
> The vga display is very slow when using latest svn with kvm enabled.
> Just try to boot any linux kernel with vesafb enabled (vga=0x314 for
> 800x600@16), enjoy watching the boot messages scroll. Booting without
> kvm enabled is *faster*.
>
Yeah, this is why we need the VGA optimization. A tight MMIO loop in
QEMU is actually pretty efficient. No code translation is needed so it
ends up being a pretty straight forward set of calls to the MMIO handler
function.
It's hugely expensive in KVM though because you have to take a huge
number of vmexits and they're pretty expensive. Anyway, the VGA
optimization will fix this nicely.
Regards,
Anthony Liguori
prev parent reply other threads:[~2008-11-07 14:02 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-11-07 9:18 [Qemu-devel] vga slow with -enable-kvm Gerd Hoffmann
2008-11-07 10:17 ` Glauber Costa
2008-11-07 14:02 ` Anthony Liguori [this message]
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