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Old 02-05-2013, 07:31 AM   #1
leechaotang
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How to force the memory in user mode to be allocated and locked?


Dear sir,

I use malloc() to allocate a 20MB memory in user mode and use mlock() to lock the memory.
But when I try to find the physical address mapping of the memory, it seems that some pages are not allocated yet. How can I allocate 20MB memory in user mode and make sure the memory is allocated physical memory and is locked?

Thanks for your kindly help!


Mark
 
Old 02-05-2013, 07:59 AM   #2
linosaurusroot
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Does it make any difference if you write random data to the 20MB you've allocated?
 
Old 02-05-2013, 10:28 AM   #3
jpollard
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The physical address will be irrelevant - it is unusable for any purpose other than physical I/O handled by drivers. The only case I know of where a single segment is reserved is for some video cards - and that memory has to be removed from the kernels view of memory before it even starts.

Your problem isn't "locked in memory", the 20MB will be scattered all over... there will be different mapping list, not a single address.

And yes, memory is NOT allocated until it is actually used.

It would be a good idea to say what you are trying to do. Maybe we could help then.

Last edited by jpollard; 02-05-2013 at 10:30 AM.
 
  


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