On Sun, Sep 01, 2002 at 01:17:15PM -0700, Mcen navaraj wrote: > what is the use of two privilege level ? To provide "protected operations" -- one process can effect other processes only by going through the kernel. > is there any performance is increase if we implement > some program in the kernel space ? It depends upon the application. In general, no. Where there may be benefits is if there are many system calls used to shuttle data between protection domains. Note that zero-copy mechanisms do exist to share data between the kernel and userspace (see NAPI) which helps avoid the problem to some great extent. But unless you can say why you think your application needs to be in the kernel, chances are good it belongs in userspace. :) > Another reason for asking this question is my > friend told the desktop in windows95 is implemented in > the kernel space. It is difficult to draw the line between userspace and kernel space in windows; it is my understanding that "the graphical interface" in windows is handled in the kernel; however, explorer, the process which handles the startmenu, window decorations, etc, is most definately a user process, so it is incorrect to say "the desktop" is implemented in the kernel -- but where exactly the line is drawn, I don't know. It would be easier to know if the source code was available for reading. :) -- It seems the power has been robbed from the founding fathers and is now firmly in the hand of the funding fathers -- Rik van Riel
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