osrm with shared memory - doubt

[rayudu3745]

HI,
I'm running osrm for us-latest with shared data approach as suggested by docs
and everything works and started without any warning or issue
but I'm doubtful whether the shared memory is using RAM or DISK
as df -h shows only 650k used shared memory
but free -g shows as 37gb

am I missing something here ? pls help

[rayudu3745]

can someone help here please