Re: 2.2.1 loosing 2 ticks: switching virtual console

H. Peter Anvin (hpa@transmeta.com)
8 Mar 1999 16:05:07 GMT


Followup to: <CF6F5640DAC@rkdvmks1.ngate.uni-regensburg.de>
By author: "Ulrich Windl" <ulrich.windl@rz.uni-regensburg.de>
In newsgroup: linux.dev.kernel
>
> Hello,
>
> I've found out that thekernel looses many ticks when I switch the
> virtual console using Alt+Fx. It could be the key combination, or it
> could be the console switching per se. I don't know which, but maybe
> someone can find it easily.
>
> (I have been working in X11 for hours, and no multiple lost ticks
> occured, but when I switchd virtual consoles, many of them appeared
> within few minutes)
>

I believe console switching is done with interrupts disabled. This is
a high-overhead operation (especially with a graphic console) with
obvious consequences.

However, something I don't seem to understand is why at least not
machines with a TSC are taught to handle missing ticks. On non-TSC
machines this information is typically not available, but TSC machines
should be able to see missing ticks by examining the TSC.

-hpa

-- 
"Linux is a very complete and sophisticated operating system.  There
are, and will be, large numbers of applications available for it."
    -- Paul Maritz, Group Vice President for Platforms And Applications,
       Microsoft Corporation [Reference at: http://www.kernel.org/~hpa/ms.html]

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