Read my reply for the related question here. http://www.spinics.net/lists/newbies/msg43910.html
On Wed, Mar 13, 2013 at 3:16 PM, Niroj Pokhrel <[email protected]>wrote: > Hi All, > > I have been studying Memory Management in linux. But I am confused with > the division of different ZONE. The use of ZONE_DMA and ZONE_NORMAL is > fine. But I am confused with ZONE_HIGHMEM, if the system is 32 bit then why > can't it map 4GB memory (2^32). I had thought that ZONE_NORMAL was for the > kernel usage so directly mapped and ZONE_HIGHMEM for the user process and > is not directly mapped to facilitate virtual addressing. But I know I am > not getting something right. While going through Ch - 15 of Rubini's Linux > Device Driver (Memory Management and DMA) I came across following line > > "a 64-bit architecture such as Intel’s x86-64 can fully map and handle > 64-bits of memory.Thus, x86-64 has no ZONE_HIGHMEM and all physical memory > is contained within ZONE_DMA and ZONE_NORMAL." So, if it can be directly > mapped why not in 32 bit architecture. > > I am really confused. Please Help. Thanking you in Advance > > > Yours, > Niroj Pokhrel > > _______________________________________________ > Kernelnewbies mailing list > [email protected] > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > > -- Regards, Prabhunath G Linux Trainer Bangalore
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