Re: [Xen-users] memory=x & maxmem=y

[Brad Plant <bplant@xxxxxxxxxxxx>]

Thanks for the very informative post Jayson,

All is sweet on my end now.

Cheers,

Brad

P.S. Good to see some other Gentoo/Xen users out there


On Mon, 21 May 2007 20:33:19 -0700
Jayson Vantuyl <jvantuyl@xxxxxxxxxxxxxx> wrote:

> The parameter is maxmem, not max-mem.  That could be part of it.
> You can get a complete list of options from "xm create
> --help_config". When I found this out it was a huge help for me.
> 
> Also, it is important that you NOT specify mem=XXX on the kernel  
> commandline (via the extra option).  That would completely break
> this behavior.  In other works, DO NOT specify anything like  
> 'extra="mem=512"'.
> 
> One other thing I've done that may affect this is that I have
> limited my Dom0 memory at boot time.  Perhaps if it has to borrow the
> memory from the Dom0 it stops short.  I do this by passing the
> hypervisor the parameter dom0_mem=524288.
> 
> Here's the relevant section of my grub.conf:
> 
> root (hd0,0)
> kernel /boot/xen.gz dom0_mem=524288 com1=38400,8n1 nmi=dom0
> module /boot/vmlinuz-2.6.16.38-xen0 root=/dev/uba1  
> netloop.nloopbacks=2 xencons=ttyS libusual.bias="ub"
> 
> And here's a lightly modified copy of the .xen file that I just
> tested:
> 
> #  -*- mode: python; -*-
> kernel = '/boot/vmlinuz-2.6.16.38-xenU'
> memory = 2000
> maxmem = 4096
> name = 'XXX'
> vif = [ 'bridge=xenbr0' ]
> disk = [
>          'phy:/dev/XXX0,sda1,w',
>          'phy:/dev/XXX1,sda2,w',
>          'phy:/dev/XXX2,sdb1,w!',
>         ]
> root = '/dev/sda1 ro'
> vcpus = 2
> 
> Here's the output of a session.  The dates are to help match up with  
> the following screenshots:
> 
> hostname ~ # date ; xm info | grep free
> Mon May 21 20:10:21 PDT 2007
> free_memory            : 307
> hostname ~ # xm mem-set XXX 2250 ; date
> Mon May 21 20:12:13 PDT 2007
> hostname ~ # xm mem-set XXX 2000 ; date
> Mon May 21 20:12:43 PDT 2007
> hostname ~ #
> 
> Here are screenshots of before adjusting the memory, after upping
> it, and after dropping it again:
> 
> http://picasaweb.google.com/jvantuyl/XenDebuggingScreenShots/ 
> photo#5067220233699865074
> http://picasaweb.google.com/jvantuyl/XenDebuggingScreenShots/ 
> photo#5067220233699865090
> http://picasaweb.google.com/jvantuyl/XenDebuggingScreenShots/ 
> photo#5067220237994832402
> 
> Here is uname -a from the DomU:
> 
> Linux XXX 2.6.16.38-xenU #1 SMP Mon Mar 26 03:15:23 PDT 2007 x86_64  
> Dual Core AMD Opteron(tm) Processor 280 GNU/Linux
> 
> And xm info on the Dom0:
> 
> host                   : XXW
> release                : 2.6.16.38-xen0
> version                : #4 SMP Mon Mar 26 22:56:07 PDT 2007
> machine                : x86_64
> nr_cpus                : 4
> nr_nodes               : 1
> sockets_per_node       : 2
> cores_per_socket       : 2
> threads_per_core       : 1
> cpu_mhz                : 2394
> hw_caps                : 178bfbff:e3d3fbff: 
> 00000000:00000010:00000001:00000000:00000003
> total_memory           : 16319
> free_memory            : 307
> xen_major              : 3
> xen_minor              : 0
> xen_extra              : .4-1
> xen_caps               : xen-3.0-x86_64
> xen_pagesize           : 4096
> platform_params        : virt_start=0xffff800000000000
> xen_changeset          : Thu Feb 15 11:34:58 2007 +0000  
> 13139:3341afbb1953
> cc_compiler            : gcc version 4.1.1 (Gentoo 4.1.1-r1)
> cc_compile_by          : root
> cc_compile_domain      : XXW.com
> cc_compile_date        : Mon Mar 26 02:54:15 PDT 2007
> xend_config_format     : 3
> 
> Hopefully some of this will help somebody...but it really does
> work. I swear!
> 
> On May 21, 2007, at 6:10 PM, suyash jape wrote:
> 
> >     Hi everyone , I have also been facing the same problem for the  
> > past few days. The max-mem parameter in the domU  config file is  
> > completely ignored.Even if we specifiy maxmem parameter in the  
> > config file at boot time , boot time allocated memory is taken as  
> > the max memory possible for the domain.
> >            Also i observed that the max vcpu parameter also
> > behaves the same way.
> > VCPU Observations:
> > 1]We can play around with only the no of VCPUs allotted at boot  
> > time or less.
> > Allocating max no of VCPUs  dynamically is not reflected. i.e we  
> > can make max VCPUs of a domain from 5 to 10 dynamically BUT the 5  
> > new ones are never used...they are always paused (possibly a bug
> > in open source xen ?)
> >
> > Is there a fix around these problems?
> >
> > Thanks.....
> >
> > Suyash
> >
> >
> >
> > Paul Archer <tigger@xxxxxx> wrote:
> >
> > > I have been playing with memory= and maxmem=, but I'm not seeing  
> > what
> > > I think I should be seeing, namely that the memory available to a
> > > domU can be increased on the fly.
> > >
> > >
> >
> > Brad wrote :
> > >I wasn't able to achieve this using xen-3.1. The maximum amount
> > >of  
> > RAM appears to be dictated by the value that >the machine is
> > booted with. Has anyone else managed to increase the amount of
> > memory allocated to a domU to >more than what the domU was booted
> > with and have the domU utilise this memory? I.e. show up with free
> > -m on the  
> > >domU?
> >
> >
> >
> >
> >
> > _______________________________________________
> > Xen-users mailing list
> > Xen-users@xxxxxxxxxxxxxxxxxxx
> > http://lists.xensource.com/xen-users
>

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