Tag Archives: performance

Windows 8 – performance issues possibly caused by KB2821895 or SuperFetch

Last week I visited my dad. He is not very familiar with computers and mainly uses it for mail, internet and viewing and editing photos. Despite my expectations, it really surprised me how fast he got used to Windows 8 (with a custom start menu).

This time though, he had some questions with regards to mail. While I was showing him how to do it, I noticed that his pc was relatively slow. Even though he doesn’t have a super fast laptop, it wasn’t this slow before.

When I took a closer look I saw that the issue was caused by high disk usage / load (I/O). At first it seemed like this was caused by TiWorker.exe which is part of Windows Modules Installer Worker and is used for installing updates. Since there were updates pending I decided to install these first just in case a fix might have been released. While these were downloading and installing I googled and found that more people were having similar sounding issues but with also high cpu usage/load. One of the the advises was to install KB2771431. This update was already installed, so it didn’t solve my issues either. I then turned off other programs that were disk I/O intensive like the backup tool Crashplan that was performing a scan and the virus scanner. Unfortunately the issue remained.

I gave the system some time just in case this was some sort of maintenance job. As the issue remainedI tried checking the system files with SFC /scannow and some files were fixed, but the disk usage was still very high.

Eventually the workaround was stopping and disabling the SuperFetch service. This is very strange since SuperFetch should make Windows faster, not slower. Since it was already late I decided not to look into it  any more at that time.

I see however that there are also issues being reported with KB2821895 that was released this month and replaces the previously mentioned KB2771431. In the known issues for KB2821895 there is mention of errors stating corruption and that you should use SFC /scannow and use the DISM tools to check and repair Windows. These symptoms do not completely match my issue, but if this doesn’t work there are also options to tune SuperFetch and Prefetch instead of turning it off completely, which is worth a shot.

So if you haven’t installed KB2771431 yet, you might want to consider postponing deployment or at least testing it very thoroughly.

To be continued …..

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Posted by on June 26, 2013 in ICT, Microsoft, Windows, Windows 8


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Intel Haswell CPU available in June with VMCS shadowing – nested virtualization

In the beginning of June, the new Intel Haswell CPUs will be available. Besides the regular improvements like being faster, having better energy efficiency and having better graphics capabilities, these new CPUs will also include VMCS shadowing (Virtual Machine Control Structure Shadowing).

Basically it’s a feature that allows you to run a hypervisor (like VMware, Hyper-V, Xen Server) and create another hypervisor as a VM beneath it. This is also called nested virtualization.

Some of you might say, “Hey this is not new, I’ve already done this with VMware!”. The difference however is that the current method uses some sort of emulation that does not directly access the hardware. And even though it’s great for testing purposes, the performance is suboptimal.

With the embedded hardware supported VMCS shadowing in the new Intel Haswell CPU the nested hypervisor can directly access the hardware, which should improve performance. Also, it might even make it possible to use non-VMware hypervisors in a nested virtualization scenario.

Of course as always, we’ll just have to wait and see how the performance will be in real-life. It’s also not clear to me yet if hypervisors need to be updated to be able to leverage this option. Nonetheless, to me it sounds very promising and I look forward to playing around with it.

For more information read this great article by Gabe Knuth called “Could VMCS Shadowing (a.k.a. nested VMs) from Intel’s new Haswell processors be what Bromium needs to work in VMs?”. When you use the links in the article you will be able to get more information about the Intel Haswell CPUs including benchmarks and more detailed information about VMCS shadowing and use cases.

[EDIT 08-06-2013] Citrix is working hard on integrating VMCS Shadowing / Nested VMs in their products:

If you’re planning to build / buy an Intel Haswell based computer or Home Lab, be sure to look into the confirmed USB3 bug in the chipset. Also unfortunately the DDR3 prices have increased substantially (almost 50%) over the last half year.


Posted by on April 29, 2013 in Hardware


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