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. -----Original Message----- From: kernelnewbies-bounce@xxxxxxxxxxxx [mailto:kernelnewbies-bounce@xxxxxxxxxxxx]On Behalf Of Tyler Sent: Thursday, July 15, 2004 1:58 PM To: kernelnewbies@xxxxxxxxxxxx Subject: Re: Physical memory Lei Yang wrote: > Hey all, > > Have a very basic question here, but it is kind of annoying me. > The kernel virtual area ( 3-4GB in virtual address) maps to the > first 1GB of physical RAM. But it is so common that we only > have a machine of 256MB/512MB etc. What is going on? > > Thanks a lot! > > Lei > The kernel has only 8MB of physical RAM allocated. And effectively, the virtual address mapped are the 3GB-4GB. This means that the user space stands from 0GB to 3GB of va (and the remaining of the physical adresses). Also note that the kernel memory is always loaded in RAM (never in swap). If you have 512 MB of RAM, 8 MB are used by the kernel and ~500 MB are use by the processes. Some part of the memory are also reserved (RAM video and ISA memory for example). > > -- > 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/ -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
