madvise() vs posix_fadvise()

[Dmitry Sivachenko]

On 21 марта 2014 г., at 20:27, Trond Endrestøl <Trond.Endrestol at fagskolen.gjovik.no> wrote:

> On Fri, 21 Mar 2014 18:56+0400, Dmitry Sivachenko wrote:
> 
>> Hello!
>> 
>> I have a program which uses large data files (read-only, via mmap()).
>> 
>> These machines have a bit more RAM that these files occupy, so it is 
>> possible to have all these data in memory.
>> 
>> What techniques should I use to promote this data not to be purged 
>> from RAM:
>> 
>> -- madvise(MADV_WILLNEED)
>> -- posix_fadvise(POSIX_FADV_WILLNEED)
>> -- both?
> 
> Although a bit dangerous, mlock(2) might be your ticket. That system 
> call prevents your memory region from being swapped/paged away from 
> physical memory.
> 


I know about mlock(2), it is a bit overkill.
Can someone please explain the difference between madvise(MADV_WILLNEED) and posix_fadvise(POSIX_FADV_WILLNEED)?