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Alex Rivera
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I am missing something when it comes to understanding the need for highmem to address more than 1GB of RAM. Could someone point out where I go wrong? Thanks! What I know: 1 GB of a processes' virtual memory (high memory region) is reserved for kernel operations. The user space can use the remaining 3 GB. This is the 3/1 split. The virtual memory features of the VM map the (continuous) virtual memory pages to physical pages (RAM). What I don't know: What operations use the kernel virtual memory? I suppose things like kmalloc(...) in kernel-space would use kernel virtual memory. I would think that 4GB of RAM could be used under this scheme. I don't get why the kernel 1 GB virtual space is the limiting factor when addressing physical space. This is where my understanding breaks down. Please advise. I've been reading this ( http://kerneltrap.org/node/2450 ), which is great. But it doesn't quite address my question to my liking.
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