On Mon, Dec 08, 2014 at 07:02:38PM +0000, Karmarkar Suyash wrote: > Hello, > > In DPDK when we use mmap why are we passing the MAP_FIXED flag when Linux man > page itself says that the option is discouraged? Any specific reason for > passing the MAP_FIXED flag? > Because theres nothing wrong with doing so. The man page says its discouraged because it creates less portable applications (due to the fact that not all operating systems support MAP_FIXED). Given that we currently only support BSD and Linux however, and given that MAP_FIXED was added to POSIX for XSI compliant systems, it seems like a reasonable thing to use, as we will most likely never run into a system that won't support it Neil
> > http://linux.die.net/man/2/mmap > > MAP_FIXED > Don't interpret addr as a hint: place the mapping at exactly that address. > addr must be a multiple of the page size. If the memory region specified by > addr and len overlaps pages of any existing mapping(s), then the overlapped > part of the existing mapping(s) will be discarded. If the specified address > cannot be used, mmap() will fail. Because requiring a fixed address for a > mapping is less portable, the use of this option is discouraged. > > > Regards > Suyash Karmarkar >
