memory balooning & page sharing

[diaolin]

I will test the memory sharing present in kvm-83.
In this manner i will use this method for the win2k machines:

http://www.linux-kvm.com/content/get-performance-boost-backing-your-kvm-guest-hugetlbfs

mkdir /hugepages
mount -t hugetlbfs hugetlbfs /hugepages
reboot
and
in rc.local
echo 296 > /proc/sys/vm/nr_hugepages

and in the VMID.conf a parameter like this

mem-path: /hugepages

If this parameter exists then the kvm startup should be the same as always with
the parameter –mem-path /hugepages

The real question for Dietmar:

could you add into the interface of "Create machine" a flag like this:

Use page sharing?

If flagged then the web interface should write the mem-path into VMID.conf

The rest is into QemuServer.pm

Is it possible to have this change?

Tx for your work Dietmar & Friends, the solution is very good.

Ciao
This week i'm not in office and despite my answer can take a little more time


Is anyone interested on this cange?

This solution can help when using multi desktop machines.

Same RAM - multiple sessions

 

[diaolin]

i've seen nobody interested on ballooning

Anyway, i'm testing the memory ballooning between multiple machines
(win2k) just for reducing memory usage.

The solution proposed by KVM is very interesting.

I hope that in the next future we'll have a button that permits to use
hugepages in the VM itself.



Ciao, Diaolin

 

[dietmar]

Hi Diaolin,

I am quite interested in that feature! But there are so much things to do ...

For now, I can add the 'args' setting in qemu-server file, in order to pass arbitrary options to kvm. Would that help for now?

- Dietmar

 

[PatrickV]

+1

Memory overcommit (with no significant negative impact on performance ?) would be a huge plus for VDI.
Please report your test results Diaolin.

 

[diaolin]

yeah, great

This can be a good work-around for the moment.

Thank's Dietmar, you are my Myth!

 

[diaolin]

of course

i would use this for VDI.

When sufficiently tested i'll report the result.

I'm also investiganting the
qemu-img growing method

Ciao

 

[bitbud]

ARGS - Please!

Hi Diaolin,

I am quite interested in that feature! But there are so much things to do ...

For now, I can add the 'args' setting in qemu-server file, in order to pass arbitrary options to kvm. Would that help for now?

- Dietmar

Dietmar, please let us know when Args is available - that would be a huge plus! I would be quite grateful to be able to pass additional options to KVM that are not yet supported in the web interface.

Thanks.

 

[dietmar]

Dietmar, please let us know when Args is available

Just uploaded the new version. Let me know it it works.

 

[diaolin]

Aaaaaaaaaaaaargs...

Thank you, Dietmar

i'll probe the args today.

Many people was interested on it.

Just a question: if i write
args: "my args"

and then i modify from interface, the chenge does not affect the args parameter. True?

 

[dietmar]

and then i modify from interface, the chenge does not affect the args parameter. True?

It does not affect the args parameter.

- Dietmar

 

[bitbud]

Dietmar - two words: THANK YOU!!!!!

That tiny little configuration option args has opened up so many options. All the features of KVM are now available to me. What a fast response too.

You guys rock - keep up the great work!

THANKS AGAIN!

 

[diaolin]

it works but...

when using the memopry paging don't forget to assign the whole
dimension to the pages.

If you use a lower dimension than the assigned to the virtual machine
if the machine uses more than the paged it hangs.

BE CAREFUL.
in any case the performance is very good, i don't know how much
but it's visible.

Diaolin
Many thanks to Dietmar

 

[mobius]

Hi

I'm trying to optimize the use of a server with a Xeon 3Ghz CPU with 1GB of RAM.
So i tried hugepages with Proxmox 1.1. to run :
1/ debian apache server (1 Cpu - 512Mb RAM / 512Mb of Swap)
2/ 2x windows XP SP3 (1 Cpu - 512Mb)

I'm not going to use the all 1GB memory when all the VMs will be running so I'm willing to use Hugetlbfs and balooning.

I've created the hugepages file sys following :
http://www.linux-kvm.com/content/get-performance-boost-backing-your-kvm-guest-hugetlbfs
I've add the following args to the VMID.conf :
mem-path : /hugepages
The command line starting the VM doesn't seem to take care of the arg in the conf file. So I used the command line with the option "-mem-path /hugepages" and it apparently worked but...
It seems that a memory reservation is made when applying hugetlbfs, cause my memory use grow from 130Mb to 860Mb...
Plus, i've succeeded in starting 1 Windows XP SP3 VM but I can't start the 2nd one (which is a copy of the first)

Without hugetlbfs, the 2 VMs start.

Do you have a hint for me?

I really want to test hugetlbfs and ballooning in my production environement so could you help me achieving my test plz

 

[mfa2004]

Hi mobius,

The proper setting in your VMID.conf file should be:

args: -mem-path /hugepages

 

[amravit]

Hi mobius,

The proper setting in your VMID.conf file should be:

args: -mem-path /hugepages

hello there
i have done same

vps:~# tail -n 5 /proc/meminfo
HugePages_Total: 7869
HugePages_Free: 7354
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 2048 kB

the strange points i need help with is

1- the host ram now showed up as fully used
Mem: 16414872k total, 16363328k used, 51544k free, 1504k buffers

2- when i run any bench mark in my windows 2003 kvm vm which have
args: -mem-path /hugepages
the load spiks some times to 3
my current system configuration

Uptime04:30:04 up 00:12, load average: 0.05, 0.65, 0.54 CPU(s)16 x Intel(R) Xeon(R) CPU X55600 @ . CPU Utilization

0.42%​

IO Delays

2.56%​

Physical Memory (15.65GB/15.59GB)

15.59GB​

Swap Space (15.00GB/42MB)

42MB​

HD Space root (94.49GB/8.32GB)

9.27%​

HD Space data (1378.03GB/9.55GB)

0.69%​

Version (package/version/build)pve-manager/1.1/3718 Kernel VersionLinux 2.6.24-3-pve #1 SMP PREEMPT Wed Feb 25 12:42:01 CET 2009 and my pveperf

CPU BOGOMIPS: 89604.27
REGEX/SECOND: 532578
HD SIZE: 94.49 GB (/dev/pve/root)
BUFFERED READS: 41.42 MB/sec
AVERAGE SEEK TIME: 21.01 ms
FSYNCS/SECOND: 900.97
DNS EXT: 242.55 ms

 

[dietmar]

BUFFERED READS: 41.42 MB/sec
AVERAGE SEEK TIME: 21.01 ms
FSYNCS/SECOND: 900.97

Did you run that when the server was idle? If so, you should consider using a faster disk system. 21ms seek time is very slow.

 

[mobius]

Hi

Thx for your help !

But in the 2nd point of my post i still doesn't understand what's happening.

It seems that a memory reservation is made when applying hugetlbfs, cause my memory use grow from 130Mb to 860Mb...
...
Without hugetlbfs, the 2 VMs start.
Do you have a hint for me?

And the memory used is less (about 780Mb)

I now succeeded in starting the two Vms with hugepages, but the memory in use grows upto 968Mb without doing anything and with a hugepages of 400mb.
It seems to be the same thing for amravit...

An idea?

thx

Mobius