Large memory usage problem in Red Hat 6.x

Step 1:  Check memory usages

# free -m

                         total       used       free     shared    buffers     cached

Mem:              16081      15848        232          0        379      13846

            Still memory utilization is very high.

 Step 2: Check value of ‘vm.vfs_cache_pressure’

# sysctl -a | grep vfs_cache_pressure

vm.vfs_cache_pressure = 100

 Step 3: Change 1000 instead of 100

# vi /etc/sysctl.conf

vm.vfs_cache_pressure = 1000

Step 4: Make value effective

# sysctl -p

vm.vfs_cache_pressure = 1000

Set /proc/sys/vm/vfs_cache_pressure at 1000, memory usage would usually hover around 700-900MB, but if anything needs lots of memory (e.g. copying lots amount of data to tmpfs) it's usage would drop back to around 100-130MB mark.

Step 5:  Check memory usages

# free -m

                         total       used       free     shared    buffers     cached

Mem:              16081      15884        197          0        379      13850

Step 6: Run below command again

# sync && echo 3 > /proc/sys/vm/drop_caches

 

Meaning of above command parameters

            echo 1 > /proc/sys/vm/drop_caches  # free pagecache, [OR]

            echo 2 > /proc/sys/vm/drop_caches  # free dentries and inodes, [OR]

            echo 3 > /proc/sys/vm/drop_caches  # free pagecache, dentries and inodes

            sync  # forces the dump to be destructive

Step 7:  Check memory usages

# free -m

                                         total       used       free     shared    buffers     cached

Mem:               16081       1166      14915          0          4        149