Re: KVM got slow after adding more physical memory to host - SOLVED

Michael Tokarev
2011-09-08T14:58:23Z

On 06.09.2011 23:22, Nikola Ciprich wrote:
> Hello guys,
>
> thanks to both of You for Your replies. The problem is solved,
> exactly as Avi said, the DMA in windows got somehow disabled.
> So this certainly was not related to adding the memory...
>
> anyways, note for further generations:
> in windows XP, the DMA usage can be checked in
> Device Manager->IDE ATA/ATAPI Controllers -> Properties->Advanced Settings
> Current Transfer Mode must be Multi-Word DMA2 or something similar,
> NOT PIO!
>
> The way I enabled this, was to uninstall both primary and secondary controller
> in device controller, then also uninstall Intel controller, and THEN rebooting (NOT sooner!)
> after reboot, controllers got detected and installed again, with DMA properly enabled.
> Note that when controller is in PIO mode, this is really a patience test, switching to DMA took
> me like half an hour to complete, so slow the system was :-/

You can open regedit and search for "NoIDE" - it should find one key
with that name, with value "1" or "yes" - just delete it, there's no
need to go that route with removing/reinstalling device drivers.

The reason why it has been disabled is - most likely - due to some
timeout while handling i/o -- eg, when your host was loaded too much
or were swapping - you should be able to find something about that
in windows event log.

/mjt