mmap performance and memory use

Wojciech Puchar wojtek at
Mon Oct 10 21:28:16 UTC 2011

> Notice that vm.pmap.pde.promotions increased by 31.  This means that 31 
> superpage mappings were created by promotion from small page mappings.

thank you. i looked at .mappings as it seemed logical for me that is shows 

> In contrast, vm.pmap.pde.mappings counts superpage mappings that are created 
> directly and not by promotion from small page mappings.  For example, if a 
> large executable, such as gcc, is resident in memory, the text segment will 
> be pre-mapped using superpage mappings, avoiding soft fault and promotion 
> overhead.  Similarly, mmap(..., MAP_PREFAULT_READ) on a large, memory 
> resident file may pre-map the file using superpage mappings.

your options are not described in mmap manpage nor 

when can i find the up to date manpage or description?

is it possible to force VM subsystem to operate on superpages when 
possible - i mean swapping in 2MB chunks?

More information about the freebsd-hackers mailing list