Hadoop Kernel Level Tuning

--Disk Swapping

--Look up existing values

cd /proc/sys/vm

cat swappiness

sysctl vm.swappiness=0

--To make swappiness permanent

vi /etc/sysctl.conf
vm.swappiness = 0

--Memory Allocation (Over Commit)

--Deny all memory requests over RAM+SWAP
vm.overcommit=0

--Approve memory requests over RAM+SWAP as defined by vm.overcommit_ratio
vm.overcommit=1

--Always approve all memory requests
vm.overcommit=2

--With 1 GB RAM; permit memory request up to 1.5 GB RAM + SWAP
vm.overcommit_ratio=50

--Look up existing values

cd /proc/sys/vm

cat overcommit_memory 
cat overcommit_ratio

--To change value online

sysctl vm.overcommit_memory=1

--To make the change permanent

vi /etc/sysctl.conf
vm.overcommit_memory=1 
vm.overcommit_ratio=50