Yes, but why is only 1GB of memory "available"? The whole address space is available to other kernels. Dave Sharp --- Rajendra <rpm@xxxxxxxxxxxxx> wrote: > The reason for the high memory is this. > > o Linux divides the address space into two parts, > user and kernel. > o Kernel gets 1 GB of address space while user > gets 3GB virtual > address space. > o Kernel needs to access all of the memory so > ideally it needs 4 GB > of virtual addresses. > o But since only 1 GB (i.e. beyond 0xc000 0000) > is available, so we > call the rest as > high memory (approx 3 GB) > o The high memory is accessed using temp. page > table entries that map > the high memory > areas in kernel address space. > o The high memory region is mostly allocated to > the user space programs. > > hope it answers the question ! > > regd, > ~rpm > Rajat Jain wrote: > > > Hi list, > > > > I recently read that the concept of "High Memory" > was introduced > > because certain architectures are capable of > physically addressing > > larger amounts of memory than they can virtually > address (physical > > address space > virtual address space). I also > read that nowadays > > "high Memory" exists only in x86. > > > > 1) Why is virtual memory > 896 MB on x86 > designated as high memory? > > AFAIK x86 has 4 GB of virtual address space > (=physical address space?) > > > > 2) Has the "high Memory" concept got anything to > do with PAE (Page > > Address Extention) feature of x86? > > > > 3) Do any other architectures than x86 have the > concept of high memory? > > > > TIA, > > > > Rajat > > - > > To unsubscribe from this list: send the line > "unsubscribe > > linux-newbie" in > > the body of a message to majordomo@xxxxxxxxxxxxxxx > > More majordomo info at > http://vger.kernel.org/majordomo-info.html > > Please read the FAQ at > http://www.linux-learn.org/faqs > > > > - > To unsubscribe from this list: send the line > "unsubscribe linux-newbie" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at > http://vger.kernel.org/majordomo-info.html > Please read the FAQ at > http://www.linux-learn.org/faqs > __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com - To unsubscribe from this list: send the line "unsubscribe linux-newbie" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.linux-learn.org/faqs
