I am running a low end laptop with I a 2.3GHz four core processor and 4GB ram. It has VT-x but not VT-d. I am experiencing very slow disk writes when using the internet and particularly when watching movies on youtube and other flash sites. Also, I experience similar slow disk writes with JQuery heavy sites. I am using Qubes 2 I think beta 2 (definitely version 2 though).
The disk write problem is very serious, the computer practically freezes for a few seconds and even up to a minute. I can see the hard drive light lit up and hear the hard drive so I am fairly certain that it is a disk write bottleneck. I may also have some network bottlenecks but I will deal with that once this issue is resolved.
Currently, I am not sure this is the ideal OS for me. I chose it mostly for the security but I understand that lack of VT-d presents a limitation here.
Looking at the Xen documentation I am led to believe that cpu pinning and limiting one core for the dom0 only would help. I have tried pinning every vcpu to its corresponding cpu in the dom and for each vm running (usually only netvm, firewallvm, and a third, generally I don’t run two appvm simultaneously) pinned each vcpu to its corresponding cpu excluding cpu 0 so I double up on each vm on one of the three remaining cpus. Thus on netvm 0-1 1-1 2-2 3-3, firewallvm 0-1 1-2 2-2 3-3 and thirdvm 0-1 1-2 2-3 3-3. I find that this does not really help.
It then occurred to me to limit the cpus to each vm but allowing the scheduler to decide on which vcpu goes with which cpu. The point is that each vm would only have access to cpus 1-3 leaving cpu 0 for the dom only.
- I am not sure if I should still pin each vcpu to its corresponding cpu number on dom0, although when I include the option dom0_vcpu_pin on grub boot options, it doesn’t seem to do that as my understanding is that it should.
- Most pertinent, I am unsure how to limit the number of cpu cores to the vm. Is it stupid of me to want 4 vcpu cores on the real cpus?
This Xen article says the option cpus=“1-3” would limit 3 cores to that particular vm. http://wiki.xen.org/wiki/Tuning_Xen_for_Performance
While this man page for qvm-prefs has an option to limit the number of vcpus but not cpus. http://qubes-os.org/trac/wiki/Dom0Tools/QvmPrefs
So as I am writing this, it occurs to me that my lack of insight is in wanting 4 vcpus to 3 cpus. Can I confirm this. Then, what I should do is use qvm-prefs to limit the number of vcpus. Nonetheless, I still would want those three to use only the cpus 1-3 and leave 0 only for dom to increase disk write speed. The problem is that I cannot find the equivalent to the cpu= option on the xen documentation in the qvm-prefs man page.
Please consider that my main purpose for writing is to resolve the disk writing bottleneck. If I am totally on the wrong track please do not hesitate to say so or if you feel that the hardware I have is inappropriate for this OS.