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Re: Protecting global lookup array
On Mon, Feb 08, 2010 at 11:40:50AM +0900, Masao Uebayashi wrote:
> I'm adding another list of vm_physseg for device pages. It's a
> list or array of physical address segments. They're frequently
> accessed by VM to lookup a physical address from a page metadata
> (vm_page) or vice versa.
> Those lists are rarely updated. When a framebuffer or
> memory-mappable audio device are attached / detached. (For RAM
> segments, they're updated when we'll support memory hot-plug. :)
> The update process is very rare, and expected. Administrators
> carefully connects a device when the machine is not running some
> important task. So what I need here is to protect such a data
> adding no run-time performance loss.
On the plus side, this is essentially the same problem as safely
switching vnodes to deadfs after a umount -f; on the minus side,
nobody's yet come up with a satisfactory solution for that...
David A. Holland
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