An Operating Systems Vade Mecum

98 Space Management Chapter 3Virtual addressKernel Base RegisterSPageOffsetKernel Page Table0 2 23PageFrame Permit PresentProcess Base RegisterPage[2..13]abcPage in process page tablePageFrame Permit PresentPage[14..22]ef512 bytesdPage FrameOffset512 bytesFigure 3.16 Address translation in the VAXthe bare machine. However, V needs to use those tables itself to manage space for thevarious P i . Therefore, each P i has its own private copy of the address-translation tables,which it uses to convert what it considers physical space into a set of virtual spaces for itsown clients. Those second-order clients have second-order virtual space.This situation is sketched in Figure 3.17. V, the virtualizing kernel, has twoclients, processes P 1 and P 2 . Each of these inhabits its own virtual machine. To keep the