Repeating keys under Fedora and Red Hat Enterprise Linux

Repeating keys under Fedora and Red Hat Enterprise Linux

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I recently ran into a case where I was seeing rapidly repeating keys under a Red Hat Enterprise Linux virtual machine.  I was also contact by one of the virtual machine MVPs who was seeing the same problem under Fedora.

After a bit of poking around it turned out that this was an extreme case of KB918461 (http://support.microsoft.com/?kbid=918461) "The system time runs too fast on a Linux-based virtual machine that is hosted in Virtual Server 2005 R2".

What is happening here is that the 2.6 kernel is using the TSC (time stamp counter) to provide a higher level of accuracy for time over just using the PIT (programmable interrupt timer).  The problem is that the TSC is highly unreliable inside of a virtual machine - and this results in all sorts of timing oddities.

The resolution proposed by this KB is to configure Linux to just use the PIT for timing - which solved my problem nicely.

Cheers,
Ben

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  • I'm interesting in you blog,and benifit more from it. Thank a lot!
    Have a nice time.
  • I also saw this same problem while trying to install Fedora Core 6 test 2 under Virtual Server R2 SP1. To do the install I needed to do a "linux clock=pit" at the bootloader screen.
  • I seem to be having a similar problem under XP. I have been using Virual PC exclusively for all of my development work for about a year, but this problem only recently appeared. Even if I set the delay and repeat rate to long and slow in the virtual PC, it has no effect and still goes too fast. Also, if I try to run online new videos, the player skips rapidly through to the end.
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