How to get linux kernel page size programmatically

Question

I am working on a Linux module for IA64. My current problem is that the driver uses the PAGE_SIZE and PAGE_SHIFT macros for dma page allocation. The problem I am having is that the machine compiling the driver is not the ones that needed to run the driver. So, if the PAGE_SIZE on the compiling machine is 2^14K and the destination machine is 2^16K then the driver fails.

I don't want to turn this question into a 'best practice' issue about compiling modules on machines which are not the ones running the modules. I understand the issues about that. What I found is that people mostly uses getpagesize() or sysconf(_SC_PAGE_SIZE). These two options are out of the ia64 kernel headers so I can't use them. Is there another way that I could get the runtime PAGE_SIZE?

Options I am looking at:

• Reading some file in /proc?
• syscall?
• Other function that let me calculate the PAGE_SIZE by inference (e.g ORDER, getpageshift, etc)?
• Other?

Answer 1

Try using the getconf utility, which will allow you to retrieve the page size easily.

getconf PAGESIZE 

Answer 2

One approximate method is to read /proc/meminfo and check Mapped size ( on mine its 52544 kB as of now ) and then check nr_mapped in /proc/vmstat ( on mine its 131136 as of now ). Finally PAGE_SIZE = Mapped/nr_mapped. Sometimes this gives you an accurate value ( as in the current example I've quoted ) and sometimes its approximate but very close. Hope this helps!