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Re: [Xen-users] Xen 3.1 terrible slowly on a laptop

  • To: carlopmart <carlopmart@xxxxxxxxx>
  • From: Nico Kadel-Garcia <nkadel@xxxxxxxxx>
  • Date: Sun, 18 Nov 2007 22:00:33 +0000
  • Cc: xen-users@xxxxxxxxxxxxxxxxxxx
  • Delivery-date: Sun, 18 Nov 2007 13:59:29 -0800
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carlopmart wrote:
Nico Kadel-Garcia wrote:
carlopmart wrote:
Nico Kadel-Garcia wrote:
carlopmart wrote:
Nico Kadel-Garcia wrote:
carlopmart wrote:
Nico Kadel-Garcia wrote:
carlopmart wrote:
Hi all,

I have installed rhel 5.1 with xen 3.1 on a laptop and ALL is terrible slowly (network, mouse, etc.) If I starts with a normal kernel (without xen enabled) all works normally. Do I need to pass any param to grub on xen enabled kernel to all works ok??

Thanks ...
Laptops are always an adventure. Do you really have enough RAM? RHEL 5 is a bit of a RAM pig. Are you using all the CPU's, or only one? Is your hard drive an ATA drive that needs "hdparm" used to set it optimally? Tell us more!

My laptop have 1 GB of RAM, and it is Pentium M 2.0Ghz. for guests I only use one cpu. And another problem is clock: lost 5 minutes every 15 min.... runs so slowly on host ...
Umm. Not good. Are you running NTP on the Dom0, and being sure not to run it on your DomU? And how much RAM did you allocatae for DomU? RHEL 5 is really, really unhappy with less than 250 Meg, and not exactly thrilled with as little as 500 Meg.

Yes, I am running ntp on dom0 and not on domU. I am suing 384 MB ram for guest, and rest for dom0.

OK. I wonder if you've got some other issues going on, such as the CPU being throttled back to do power saving. But what does "free" say in DomU about your available RAM? Are you swapping? And are you using a file image, or an LVM partition? And when you built the image, if you used a file image, did you make sure that it's not "sparse"?

oops i think that you point me to the problem. I am using a sparse file for guest disk ... Is this really a problem?? Can't i use sparse files on a laptop??? And yes I have activated power saving ...
I've not played with it much, but using sparse files seems to be an awful idea until you've actually populated the file system through use. This means that your first system operations, such as installing software, compiling new tools, or building new databases, are goiing to suffer horribly from it.

I also can't help thinking that your Dom0 may not have its hard drive set up correctly: if you're using an IDE or ATA drive, check what "hdparm" says about it. You may get a huge performance benefit from a "hdparm -d1c1 /dev/hda" or from setting up your sysconfig setttings correctly for a contemporary ATA drive.

My guest config is:

kernel = "/boot/vmlinuz-2.6.9-67.ELxenU"
ramdisk = "/boot/initrd-2.6.9-67.ELxenU.img"
bootloader = "/usr/bin/pygrub"
WHOAH. Hold it right there. Why are you using those kernel and ramdisk settings in company with the pygrub? You don't need them, and you probably added them manually, rather than using virt-install, right?

Comment them out and just use the pygrub.

name = "RhelUpdates"
memory = "384"
maxmem = "384"
disk = [ 'tap:aio:/data/xenvmguests/rhel4updates/rhel4vol01.xvda,xvda,w' ]
vif = [ 'type=ieomu, mac=00:16:31:a5:67:13, bridge=natxenbr0' ]
vcpus = 1
on_reboot = 'restart'
on_crash = 'destroy'
sdl = 0
vnc = 1
vfb = [ 'type=vnc,vncunused=1' ]

I think that hdparm returns correcty parameters:
 multcount    = 16 (on)
 IO_support   =  0 (default 16-bit)
 unmaskirq    =  0 (off)
 using_dma    =  1 (on)
 keepsettings =  0 (off)
 readonly     =  0 (off)
 readahead    = 256 (on)
 geometry     = 16383/255/63, sectors = 156301488, start = 0

DMA it is activated, and this disk is IDE, I am not sure if I can activate 32 bits transfer using -c1 option on hdparm.
Almost any hard drive made this millennium can use 32-bit: the IDE defaults (more typically PATA now!) are set extremely, extremely low performance for backwards compatible reasons, and really should be updated. I once spent a long argument with a kernel developer about how "the kernel picks the higher performance default!" and had to walk him through the code that showed him, no, the kernel preserved what it was set to the lat time it was warm-rebooted. It you actually power off, it resets to to the lower settings and stays there until manually reset. It led to a huge performance improvement and the cost savings of buying a lot of big SCSI drives that had a serious kernel compatibility issue (due to this developer's insistence on backporting everything from new kernels instead of forward porting their modifications to a contemporary kernel: b-r-r-r-r!
If I don't put which kernel image needs to startup on guest system with kernel and ramdisk params, I can't start guest. Pygrub returns a lot errors about doesn't find a valid kernel image.
Ahh. Do you have the matching kernel installed in your guest domain, so that insmod can find them and install them? It definitely looks like you've not successfully loaded the boot loader in a way that grub can find it. Can you run "grub-install /dev/xvda1" from your working DomU environment?
 I will try to use a complete file image, and not sparse file ...

Cool. That's one source of performance issues to check.

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