Many times Linux systems faced low memory issues,This article has details about how to Flush Memory Cache on Linux Server.There are three options available to flush cache of Linux memory. You can use one of below as per your requirements.
To free pagecache, dentries and inodes in cache memory use:
sync; echo 3 > /proc/sys/vm/drop_caches
To free dentries and inodes use following command:
sync; echo 2 > /proc/sys/vm/drop_caches
If to free pagecache only use following command:
sync; echo 1 > /proc/sys/vm/drop_caches
You can also schedule following in crontab to automatically flush cache on regular basis.
crontab -e 0 * * * * sync; echo 3 > /proc/sys/vm/drop_caches