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I assume, given the above, that the motivation for this is that you're trying to set things up such that pointers in the shared memory all have the same addresses in each of the processes, and that means you want to reserve the same block of address space no matter what. Kind regards, That's 2^16 * 2^32 = 64K *4GB = 256TB. -- Terry

Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev@lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.appl... On Sep 22, 2009, at 3:35 AM, Alastair Houghton <alastair@alastairs-place.net

wrote:

On 22 Sep 2009, at 11:19, Jay Reynolds Freeman wrote: Correct. Have you tried using the "vmmap" tool to investigate the virtual memory map of the process that you're having trouble with? That should enable you to investigate where the free regions of VM are likely to be at the correct point in your program's execution. I'm not sure what the precise virtual address space limits are for OS X---there's probably a tech. note somewhere, but someone here will know in any case---but it should be easy enough to locate a region that's large enough for your purposes. Alastair. There is an architectural limit of 48 bits on Intel processors, which is documented, well, pretty much everywhere anyone who is doing code generation is looking at Intel documentation. So I'm pretty sure your approach of finding a large hole in the middle of the available virtual address space and just using it for a fixed mapping will work fine. I definitely would NOT put the hole in the heap using static allocations to get mapping set up by the kernel image loader, whose job is really to get something (hopefully not a huge amount of that something) into memory rather crudely, then hand over control to dyld to do the rest. That said, unless you have a metric ton of memory, mapping 320GB into your address space will take a lot of wired pages to represent the pmap and other data structures needed to provide the mapping for that many pages, so I probably would not be trying this on a machine with a 32 bit kernel and a lot of physical RAM. 320GB / 1 page per 4MB stride for a 64 bit pmap works out to 80K pages of page mappings, or 320MB not counting other overhead: a good argument for mapping windows instead of direct mapping everything. This email sent to site_archiver@lists.apple.com