Xen users - Jan 2006 - a performance question

Hello all,

First of all I''d like to thank everyone for making Xen so user
friendly. I thought I''d be sweating through this but it''s been
pretty
straight forward (thanks to all the different tutorials on the net).

I''ve got a domU that I created with
dd if=/dev/zero of=vm_base.img bs=1024k count=4000
mkfs.ext3 vm_base.img
dd if=/dev/zero of=vm_base-swap.img bs=1024k count=1000
mkswap vm_base-swap.img
mount -o loop vm_base.img /mnt
debootstrap etch /mnt

this has worked fine and I''m happily continuing with the installation

But.
I have a performance question. For example.
vi /etc/hosts (or any other file)
will take about five seconds to open the first time I use
''vi'', but
after that it opens files as fast as expected.

This seems to repeat itself with other programmes.
kdm_greet takes way too long the first time, but from then on it starts up ok.

Can anyone explain this to me?

Thank you
Chris.

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> I have a performance question. For example.
> vi /etc/hosts (or any other file)
> will take about five seconds to open the first time I use
''vi'', but
> after that it opens files as fast as expected.
after reading the xen3 user manual again, it is suggested that high
I/O apps on a file image may not work too well.

I don''t really consider opening a file with vi to be very disk
intensive, but I''ve moved the domu installation off the img file onto
a lvm disk just to see.
- No real improvement.
So I threw more ram at both dom0 and domU.
Now I''m wating 3 seconds instead of 5.

What sort of reults should I be expecting?
I''m using a AMD XP 2000+ cpu @ 1658 MHz and 256KB cache
I''ve got a total of 512MB of ram
The disk is IDE.

Thanks
Chris.

On 1/19/06, Chris Fanning <christopher.fanning@gmail.com>
wrote:
> Hello all,
>
> First of all I''d like to thank everyone for making Xen so user
> friendly. I thought I''d be sweating through this but it''s
been pretty
> straight forward (thanks to all the different tutorials on the net).
>
> I''ve got a domU that I created with
> dd if=/dev/zero of=vm_base.img bs=1024k count=4000
> mkfs.ext3 vm_base.img
> dd if=/dev/zero of=vm_base-swap.img bs=1024k count=1000
> mkswap vm_base-swap.img
> mount -o loop vm_base.img /mnt
> debootstrap etch /mnt
>
> this has worked fine and I''m happily continuing with the
installation
>
> But.
> I have a performance question. For example.
> vi /etc/hosts (or any other file)
> will take about five seconds to open the first time I use
''vi'', but
> after that it opens files as fast as expected.
>
> This seems to repeat itself with other programmes.
> kdm_greet takes way too long the first time, but from then on it starts up
ok.
>
> Can anyone explain this to me?
>
> Thank you
> Chris.
>
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Xen-users mailing list
Xen-users@lists.xensource.com
http://lists.xensource.com/xen-users

Hi
Chris Fanning wrote:
> I don''t really consider opening a file with vi to be very disk
> intensive, but I''ve moved the domu installation off the img file
onto
> a lvm disk just to see.
> - No real improvement.
> So I threw more ram at both dom0 and domU.
> Now I''m wating 3 seconds instead of 5.
> 
May not be applicable to your situation, but I had something similar 
happen with emacs on some of my images - however once networking was 
setup and working the start delay went away.  I can only assume that it 
was making a call to get the host name (or some such) and hitting a 
network timeout.

David.

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