Look at this, "The kernel virtual area (3 - 4 GB address space) maps to the first 1 GB of physical RAM." and the figure, you think it is right? I thought this is misleading, since it gives the feeling that the whole first 1GB of physical RAM is reserved for kernel use, which it is certainly not (otherwise a machine with 1.5 GB RAM would only give 512 MB max physical RAM to userspace processes...) -----Original Message----- From: kernelnewbies-bounce@xxxxxxxxxxxx [mailto:kernelnewbies-bounce@xxxxxxxxxxxx]On Behalf Of Tyler Sent: Thursday, July 15, 2004 7:03 PM To: kernelnewbies@xxxxxxxxxxxx Subject: Re: Physical memory Lei Yang wrote: > Thanks a lot for the information! > I get the idea of 1GB physical RAM mapped to 1GB virtual memory for kernel from this link: > http://kerneltrap.org/node/view/2450 > I guess it's just wrong. > I think there's no error in this text (I haven't read it all). But each process has a different adress space (4GB each). In these 4GB, 3 are for the user space and 1GB for the kernel (for the stuff that the process do in kernel space). But you have to understand for each process, for example the adress 0x4565 is mapped (or can be mapped) to a different physical adress. This is done by using different page table. And don't confuse kernel and kernel space. -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/ -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
