how to get exact number of bytes accessible in RAM for a 32 Bit app?
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Is there a function available that can return the Maximum number of bytes accessible in RAM for a 32 Bit App? It might be running on either 32 or 64 Bit machines. I know of the flag /LARGEADDRESSAWARE. What I am specifically looking for is a function that can tell me the number of bytes as numeric quantity.
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Is there a function available that can return the Maximum number of bytes accessible in RAM for a 32 Bit App? It might be running on either 32 or 64 Bit machines. I know of the flag /LARGEADDRESSAWARE. What I am specifically looking for is a function that can tell me the number of bytes as numeric quantity.
Try GlobalMemoryStatusEx[^] maybe.
> The problem with computers is that they do what you tell them to do and not what you want them to do. < > If it doesn't matter, it's antimatter.<
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Is there a function available that can return the Maximum number of bytes accessible in RAM for a 32 Bit App? It might be running on either 32 or 64 Bit machines. I know of the flag /LARGEADDRESSAWARE. What I am specifically looking for is a function that can tell me the number of bytes as numeric quantity.
Hi Divya, The maximum virtual address can be determined by doing something like:
SYSTEM_INFO si = {0};
GetSystemInfo(&si);
DWORD_PTR dwMaximumAddress = (DWORD_PTR)si.lpMaximumApplicationAddress;If you wanted to determine if the physical address extensions are enabled on a 32 bit OS you could then do something like:
BOOL bPAE = ((DWORD_PTR)si.lpMaximumApplicationAddress >= 0xBFFFFFFF);
Best Wishes, -David Delaune
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Is there a function available that can return the Maximum number of bytes accessible in RAM for a 32 Bit App? It might be running on either 32 or 64 Bit machines. I know of the flag /LARGEADDRESSAWARE. What I am specifically looking for is a function that can tell me the number of bytes as numeric quantity.
As mentioned, GetSysInfo() will give you the physical memory, but then you have to ask yourself why you want to know this since half of this is physically reserved for the kernel, but the virtual memory each process runs in will be addressable memory up to 4 GB regardless of what you have physically. So, what are you trying to do and why?
============================== Nothing to say.
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Hi Divya, The maximum virtual address can be determined by doing something like:
SYSTEM_INFO si = {0};
GetSystemInfo(&si);
DWORD_PTR dwMaximumAddress = (DWORD_PTR)si.lpMaximumApplicationAddress;If you wanted to determine if the physical address extensions are enabled on a 32 bit OS you could then do something like:
BOOL bPAE = ((DWORD_PTR)si.lpMaximumApplicationAddress >= 0xBFFFFFFF);
Best Wishes, -David Delaune
Thanks a ton, David! I will try to figure out what to do with those details.
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As mentioned, GetSysInfo() will give you the physical memory, but then you have to ask yourself why you want to know this since half of this is physically reserved for the kernel, but the virtual memory each process runs in will be addressable memory up to 4 GB regardless of what you have physically. So, what are you trying to do and why?
============================== Nothing to say.
Eric, what I am trying to find is 'guess-timate' (I finally found an occasion to use this word) the amount of memory available to my application (a rather loose statement, I know.. but hopefully gives the idea). An algorithm in the app that needs quite a lot of memory would need to know if that memory is available or not. Its a dedicated app, there is little chance of some other app requesting a large chunk of memory in parallel. The memory the algorithm will use is known (or can be approximately figured out based on the input data). So I was hoping that these 2 numbers (available memory and needed memory) would help in a quick decision making as to whether we should proceed with the processing or not. thanks for the reply!
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Eric, what I am trying to find is 'guess-timate' (I finally found an occasion to use this word) the amount of memory available to my application (a rather loose statement, I know.. but hopefully gives the idea). An algorithm in the app that needs quite a lot of memory would need to know if that memory is available or not. Its a dedicated app, there is little chance of some other app requesting a large chunk of memory in parallel. The memory the algorithm will use is known (or can be approximately figured out based on the input data). So I was hoping that these 2 numbers (available memory and needed memory) would help in a quick decision making as to whether we should proceed with the processing or not. thanks for the reply!
OK, so in fact you can allocate a massive chunk of memory, because the system will page it out for you if it cant physically fit in RAM. (It will page it out in pages, 4k chunks, so you might want to organise your memory usage so commonly used stuff is on the same page(s) in order to keep it resident in memory)
============================== Nothing to say.
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Eric, what I am trying to find is 'guess-timate' (I finally found an occasion to use this word) the amount of memory available to my application (a rather loose statement, I know.. but hopefully gives the idea). An algorithm in the app that needs quite a lot of memory would need to know if that memory is available or not. Its a dedicated app, there is little chance of some other app requesting a large chunk of memory in parallel. The memory the algorithm will use is known (or can be approximately figured out based on the input data). So I was hoping that these 2 numbers (available memory and needed memory) would help in a quick decision making as to whether we should proceed with the processing or not. thanks for the reply!
Also note that "available memory" != "biggest continous block you can allocate". What i mean is something like this: [1 MB of free memory][2 MB of already allocated memory][3 MB of free memory] If you query the amount of free memory, you get 4 MB, if you try to allocate a 4 MB block, it will fail because the biggest continous free chunk is only 3MB. I'm just sayinmg because we ran into this already once or twice... :)
> The problem with computers is that they do what you tell them to do and not what you want them to do. < > If it doesn't matter, it's antimatter.<
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Thanks a ton, David! I will try to figure out what to do with those details.
Divya, marking his reply as answer will help others know that it's a good answer and that it helped you. I've marked it now, and you can too.
"Real men drive manual transmission" - Rajesh.