[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2
From: |
Gleb Natapov |
Subject: |
Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35? |
Date: |
Wed, 4 Aug 2010 18:25:52 +0300 |
On Wed, Aug 04, 2010 at 09:57:17AM -0500, Anthony Liguori wrote:
> On 08/04/2010 09:51 AM, David S. Ahern wrote:
> >
> >On 08/03/10 12:43, Avi Kivity wrote:
> >>libguestfs does not depend on an x86 architectural feature.
> >>qemu-system-x86_64 emulates a PC, and PCs don't have -kernel. We should
> >>discourage people from depending on this interface for production use.
> >That is a feature of qemu - and an important one to me as well. Why
> >should it be discouraged? You end up at the same place -- a running
> >kernel and in-ram filesystem; why require going through a bootloader
> >just because the hardware case needs it?
>
> It's smoke and mirrors. We're still providing a boot loader it's
> just a little tiny one that we've written soley for this purpose.
>
> And it works fine for production use. The question is whether we
> ought to be aggressively optimizing it for large initrd sizes. To
> be honest, after a lot of discussion of possibilities, I've come to
> the conclusion that it's just not worth it.
>
> There are better ways like using string I/O and optimizing the PIO
> path in the kernel. That should cut down the 1s slow down with a
> 100MB initrd by a bit. But honestly, shaving a couple hundred ms
> further off the initrd load is just not worth it using the current
> model.
>
The slow down is not 1s any more. String PIO emulation had many bugs
that were fixed in 2.6.35. I verified how much time it took to load 100M
via fw_cfg interface on older kernel and on 2.6.35. On older kernels on
my machine it took ~2-3 second on 2.6.35 it took 26s. Some optimizations
that was already committed make it 20s. I have some code prototype that
makes it 11s. I don't see how we can get below that, surely not back to
~2-3sec.
> If this is important to someone, we ought to look at refactoring the
> loader completely to be disk based which is a higher performance
> interface.
>
> Regards,
>
> Anthony Liguori
>
> >David
>
> --
> To unsubscribe from this list: send the line "unsubscribe kvm" in
> the body of a message to address@hidden
> More majordomo info at http://vger.kernel.org/majordomo-info.html
--
Gleb.
- Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35?, (continued)
- Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35?, Alexander Graf, 2010/08/04
- Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35?, Anthony Liguori, 2010/08/04
- Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35?, Avi Kivity, 2010/08/04
- Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35?, Anthony Liguori, 2010/08/04
- Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35?, Alexander Graf, 2010/08/04
- Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35?, Avi Kivity, 2010/08/04
- Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35?, Jamie Lokier, 2010/08/03
- Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35?, Avi Kivity, 2010/08/04
- Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35?, David S. Ahern, 2010/08/04
- Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35?, Anthony Liguori, 2010/08/04
- Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35?,
Gleb Natapov <=
- Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35?, Alexander Graf, 2010/08/04
- Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35?, Gleb Natapov, 2010/08/04
- Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35?, Alexander Graf, 2010/08/04
- Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35?, Gleb Natapov, 2010/08/04
- Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35?, Avi Kivity, 2010/08/04
- Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35?, Kevin O'Connor, 2010/08/04
- Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35?, Gleb Natapov, 2010/08/05
- Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35?, Anthony Liguori, 2010/08/03
- Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35?, Avi Kivity, 2010/08/03
- Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35?, Richard W.M. Jones, 2010/08/03