Memory allocation for 32-bits application

Posted by mailliwal@reddit | sysadmin | View on Reddit | 5 comments

Hi, For 32-bits, maximum memory allocation is 4GB. If I run same 3 x 32-bits application, may I know : - 3 application will share 4GB or - each application can allocation 3 x 4GB (max 12GB) ? Thanks

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5 Comments

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Dopeykid666@reddit

The maximum may be 4gb, but most 32gb applications will only actually use a max of 2gb, as they were designed to run on 32bit machines that were also limited to 4gb. As such, depending on the application, it is likely limited to 2gb with the other 2gb being reserved for system use. Iirc this is just a flag within the exe that can be easily changed, so not a huge deal but something I thought was worth pointing out.

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mailliwal@reddit (OP)

If the 32-bits application showed 3 tasks, like abc.exe in task manager. Then each abc.exe could use 2 GB (6GB max) ? Furthermore, is different to run 32-bits application on 32-bits OS or 64-bits OS ?

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Dopeykid666@reddit

Do you feel as though your questions have been answered?

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mailliwal@reddit (OP)

Yes

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Caldazar22@reddit

Yes, if 32-bit virtual address spaces are configured to split the address space to allow user-mode allocations of up to 2GB, then three processes could allocate up to 6GB. Yes, architecturally, running a 32-bit process on a 32-bit OS kernel is different than running 32-bit processes on a 64-bit OS kernel. The 64-bit kernel has to be able to map calls to the appropriate 32-bit vs. 64-bit libraries and, in some cases, different filesystem paths.