>> Hi all, >> The following link gives the memory map for the arm architecture. >> http://www.arm.linux.org.uk/developer/memory.txt >> >>I have the following doubts.. >>1) Any chipset(based on arm) manufacturer(qualcom,samsung..) should follow >>the same memory map. >>Is it hardly constrained or can be changed? >>Where are this constraints are implemented in the kernel source tree?
>you mean, device memory map? well AFAIK that is dictated by >BIOS....kernel simply just follow along... Not the device memory map..others also like vmalloc()/ioremap region, dma_alloc() (refer that link) these regions. i refered to qualcomm chipset memory map(based on ARM9). They just mentioned only where different devices were mapped. They doesnt have this specifc adress space constraints for vmalloc, ioremap,dma_alloc etc., So i thought it is taken care by kernel. Please tell me where these constraints will be implemented? Another clarification, while assigning memory through vmalloc(), dma_alloc() kernel first should check the available address space 'taking the constraints into consideration' before returning the addresses, right? On Tue, May 31, 2011 at 12:32 PM, Mulyadi Santosa <mulyadi.sant...@gmail.com > wrote: > Hi... > > I am not ARM guy, but I'll see what I can share here..... hold your breath > :) > > On Tue, May 31, 2011 at 12:54, sandeep kumar <coolsandyfor...@gmail.com> > wrote: > > Hi all, > > The following link gives the memory map for the arm architecture. > > http://www.arm.linux.org.uk/developer/memory.txt > > > > I have the following doubts.. > > 1) Any chipset(based on arm) manufacturer(qualcom,samsung..) should > follow > > the same memory map. > > Is it hardly constrained or can be changed? > > Where are this constraints are implemented in the kernel source tree? > > you mean, device memory map? well AFAIK that is dictated by > BIOS....kernel simply just follow along... > > > > > 2) while i was student, i read in OS concepts that, "Virtual memory > gives an > > illusion to a process, > > that it has always a larger continuous address space (even more than RAM) > > available to it." > > that's true... but you need to count another limitation: addressable > or not by the MMU or at least processor itself? > > let's say you have 16 GiB of virtual memory, composed of 4 GiB of RAM > + 12 GiB swap. Theoritically, a single process should be able to use > them all, but assuming we have no PAE enabled, an 32 bit system could > only address up to 4 GiB > > > So i thought i could allocate howmuch ever memory i want. > > Also think about fragmentation... > > > But seeing the above link,i observed there is some limitation in the > address > > space created by the vmalloc(). > > So i m now thinking that vmalloc has some limit. > > Yup..... > > maybe my old article could shed a light further for you: > http://linuxdevcenter.com/pub/a/linux/2006/11/30/linux-out-of-memory.html > > -- > regards, > > Mulyadi Santosa > Freelance Linux trainer and consultant > > blog: the-hydra.blogspot.com > training: mulyaditraining.blogspot.com > -- With regards, Sandeep Kumar Anantapalli, Senior Software Engineer, Samsung India Software Operations, Bangalore.
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