On Wednesday 28 February 2007 10:47, Sandeep Sanjay Patil wrote: > > So what you are saying that on a 1gb,2gb,..,4gb ram, ZONE_HIGH_MEM will > > always be 128mb. However, those 128mb in the MMU will not enjoy identity > > mapping (i.e. will have to use page tables entries translations). In > > addition, if we have 4gb ram, the additional physical 3gb after the first > > 1gb. i.e. 0x40000000 - 0xffffffff will be mapped to virtual addresses 0x0 > > - 0xc0000000? (major weirdness btw). > > No, AFAIK the last 128mb will be dynamically changed to use the > physical memory above 896mb. If not to be used in the kernel, the higher > physical addresses will only be mapped for the applications... CMIIW... What do you mean by dynamically. Applications, from what i understand, can allocate in physical memory wherever they want (translated, wherever the kernel wants in there) in the free normal/dma/himem zones (as long as it is not used by the kernel). I.e. this allocation to high mem, i think, should not be different from the kernel usual allocation. > > > Btw, when i only have 512mb. Does that mean that the virtual address > > which is in excess of the virtual-physical ram identity mapping, (if i > > have enough swap space) will be from 0x0-0xc0000000? > > I didnt really get this part... What i meant to ask was. Even if we have 512mb ram in the system, each process can address from 0gb-3gb virtual address space? and it will be taken from normal/dma/himem+ zones where ever it is free in physical memory right? Though i did not get if there is some order/rule to that allocation in physical memory. > > > Btw, is it also possible for two processes to have the same virtual > > address and context switch will redirect each time (using different page > > table of the process) the same virtual address to different physical > > address. > > This is what happens... Really, cool. At the beginning i thought that all processes can address only 0-3gb of virtual memory together and not 0-3gb each (as it is really is). Though, i knew each process lives in it's own world where it thinks it runs alone having the processor to itself. > > cheers > sandeep -- Regards, Tzahi. -- Tzahi Fadida Blog: http://tzahi.blogsite.org | Home Site: http://tzahi.webhop.info WARNING TO SPAMMERS: see at http://members.lycos.co.uk/my2nis/spamwarning.html -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
