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Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2

From: Avi Kivity
Subject: Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35?
Date: Wed, 04 Aug 2010 20:50:12 +0300
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv: Gecko/20100720 Fedora/3.1.1-1.fc13 Thunderbird/3.1.1

 On 08/04/2010 08:46 PM, Richard W.M. Jones wrote:
On Wed, Aug 04, 2010 at 07:36:04PM +0300, Avi Kivity wrote:
This is basically my suggestion to libguestfs: instead of generating
an initrd, generate a bootable cdrom, and boot from that.  The
result is faster and has a smaller memory footprint.  Everyone wins.
We had some discussion of this upstream&  decided to do this.  It
should save the time it takes for the guest kernel to unpack the
initrd, so maybe another second off boot time, which could bring us
ever closer to the "golden" 5 second boot target.

Great.  IMO it's the right thing even if initrd took zero time.

It's not trivial mind you, and won't happen straightaway.  Part of it
is that it requires reworking the appliance builder (a matter of just
coding really).  The less trivial part is that we have to 'hide' the
CD device throughout the publically available interfaces.  Then of
course, a lot of testing.

I will note that virt-install uses the -initrd interface for
installing guests (large initrds too).  And I've talked with a
sysadmin who was using -kernel and -initrd for deploying VM hosting.
In his case he did it so he could centralize kernel distribution /
updates, and have the guests use /dev/vda == filesystem which made
provisioning easy [for him -- I would have used libguestfs ...].

We still plan to improve pio speed.

(note a few added seconds to guest install or bootup is not such a drag compared to the hit on an interactive tool like libguestfs).

I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.

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