debian jessie as kvm guest high cpu load


I was wondering about the high cpu load of my debian jessie kvm guests.

 18 root 20 0     S           11,0      50:10.35 ksoftirqd/2
 28 root 20 0     S           11,0      49:45.90 ksoftirqd/4
 13 root 20 0     S           10,1      51:25.18 ksoftirqd/1
 23 root 20 0     S           10,1      55:42.26 ksoftirqd/3
 33 root 20 0     S           8,3       43:12.53 ksoftirqd/5
 3 root 20 0      S           7,4       43:19.93 ksoftirqd/0

The more load my kvm guest had the more cpu time was allocated by the kernel.
I was using 3.16.0-4-amd64.

My hostmachines were, ubuntu 14.04 and archlinux. Both same issue.

Simple solution was to install backports kernel 4.2.0-0.bpo.1-amd64 oder compile fresh vanilla kernel via make localyesconfig.

Seems to be a debian kernel bug.

Have fun!

adaptec 5805zq Host adapter abort request vmware 5.5 high I/O load


After 1/2 year waiting for a FIX for that issue, Adaptec fixed it:

Adaptec support wrote:


We have been able to identify the cause of this problem as an issue that occurs when using the MSI-X legacy interrupt type with Intel V2 processors, in conjunction with ESXi 5.5. The problem can be worked around with the latest 40701 driver, which can be downloaded here:
And adding the driver parameter " MSI=1" for the aacraid module, as such.
SSHclient# system module parameters set -m aacraid --parameter-string "msi=1"
After having done this, you will need to reboot the system.
After reboot, to be sure that MSI is set, do this:
# lspci | grep Adap
0000:04:00.0 Mass storage controller: Adaptec AACRAID [vmhba0]
~ # dmesg | grep MSI
2014-11-17T14:07:04.222Z cpu2:33395)<6>igb 0000:02:00.1: Using MSI-X
interrupts. 1 rx queue(s), 1 tx queue(s)
2014-11-17T14:07:09.712Z cpu10:33502)Enabling MSI for dev 0000:04:00.0
This workaround applies to Series 5 and Series 6 controllers. Series 7 and 8 controllers would not be affected by the problem.


Hope this will help someone who’s running in this issue

Have fun!

apache2 reverseproxy for single virtualhost


need to reverseproxy a webite with apache?
following config for following scenario:

your webserver A is running on ip with
but you want that webserver B running proxying to webserver A

then put the following config in your configuration file of webserver B:

<VirtualHost *:80>
         <Proxy *>
                Order deny,allow
                Allow from all
         ProxyPreserveHost On
         ProxyPass /
         ProxyPassReverse /

If you are wondering what the option “ProxyPreserveHost” is read here:
http://httpd.apache. … ml#proxypreservehost
don’t forget to change dns settings.

Have fun!