Windows 8 update bug clogs CPUs

June 14, 2013 // 8:38 a.m.

Tags: #bug #dism #kb2821895 #microsoft #patch-tuesday #windows #windows-8 #windows-rt #windows-server-2012 #windows-update

A bug introduced in the latest update for Windows RT, Windows 8 and Windows Server 2012 is reportedly causing performance problems for many users.

Released earlier this week as part of the company's monthly Patch Tuesday update cycle, KB2821895 is designed to update the servicing stack - the portion of the operating system used by Windows Update - to add much-needed improvements. Among the features tweaked or added by the update are the ability to install previously downloaded updates without an active internet connection, a reduction in certain software sizes, and the automatic compression of unused binary files when updates are installed.

While many of the new features are targeted more at tablet users than desktop users, the update was released to all Windows 8, Windows RT and Windows Server 2012 users on Tuesday. Sadly, it soon transpired that there was a problem: with the update installed, users began to report that processes related to the analysis of system files - in particular the TiWorker.exe application, part of the Microsoft System File Checker tool - would take up masses amounts of processor time, locking cores with between 40 and 100 per cent utilisation until failing with an error.

During this time, a logfile - CBS.log - is seen to rapidly grow with entries that show files being marked as damaged, then unable to be repaired. These files, however, do not appear to be actually damaged, and the system runs as normal - albeit slowly - while the error is occuring.

Not everyone who has installed the patch has reported the problem, and thus far it's not clear what is causing the issue on systems that are affected. With KB2821895 not valid for uninstallation, however, a workaround is needed for those that are suffering from the glitch - and, thankfully, there is one.

According to a member of the German-language Dr. Windows forum, which was one of the first sites to spot the problem, the issue can be solved by running the Deployment Image Servicing and Management (DISM) command below with administrative privileges:

DISM /online /cleanup-image /restorehealth

While this process takes some time, it should prevent the CPU from being overloaded with spurious analysis and error logging. Thus far, Microsoft has not commented on the flaw in the update, nor has it indicated any plans to release a patch of its own for the issue.

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