slab and sreclaimable used up most RAM

One of the server few days ago used up almost all available memory.

free -m shows the following:

             total       used       free     shared    buffers     cached
Mem:         31941      31112        828          1        169       1563
-/+ buffers/cache:      29379       2562
Swap:         1023          0       1023

After did some research, issuing the following commands prompted high memory usage on the slab and sreclaimable for the dentry kernel process:

slabtop
vmstat -m

To free up the memory, i used the following:

sync; echo 3 > /proc/sys/vm/drop_caches

and the result:

             total       used       free     shared    buffers     cached
Mem:         31941        971      30969          1          7        103
-/+ buffers/cache:        861      31080
Swap:         1023          0       1023

Will this permanently resolve the memory issue? i think it will not but will keep monitoring, suspected it was due to recent use of nixstats which caused this memory issue due to frequest SSL request (curl or libcurl).