How to free up RAM being used by MongoDB?

When Mongodb has ran for too long it eats up the RAM on my server thus leaving little room for other processes. I read somewhere that restarting mongodb makes it write the data to the disk and thus free up the RAM. I restarted it using:

sudo service mongodb restart

But that didn’t affected the RAM. Then I rebooted the server which did freed up the RAM. My question is that why restarting mongodb doesnt make it write the cache to the disk but rebooting does? Rebooting is not a viable option always. How can I make it write out the data to disk without rebooting?


mongoDB works in same manner that takes RAM for better performance.

if you are wants to free memory with out rebooting the server then you can use.

echo 3 > /proc/sys/vm/drop_caches

better to schedule this ^ command in cron .

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Also, what amount of memory do you have on your server? You may need to increase the amount of memory in order to use MongoDB effectively. Usually we recommend running MongoDB on its own server, and not sharing that server with other applications.