Erik Mouw wrote: > > High memory only matters if you have >4GB in your machine (on x86). > The CPU can't address all of the 4GB, so all the memory above the 4GB > is called high memory. Minor correction: High memory only matters if you have >1GB (or so) in your machine (on x86). The kernel can't directly map all of the 1GB into its virtual address space, so all the memory above the 1GB is called high memory. This difference should have few practical consequences for user code. The kernel allocates high memory when it can, low memory when it must, and the distinction is entirely transparent to user code. Within the kernel, however, high-memory pages cannot be addressed until they are passed through kmap(). The 4GB thing is for "Page Addressing Extensions" - you must have a PAE-enabled kernel (and CPU) in order to use memory beyond 4GB. Cheers, -- Joe "I should like to close this book by sticking out any part of my neck which is not yet exposed, and making a few predictions about how the problem of quantum gravity will in the end be solved." --- Physicist Lee Smolin, "Three Roads to Quantum Gravity" -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ IRC Channel: irc.openprojects.net / #kernelnewbies Web Page: http://www.kernelnewbies.org/
