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Memory Monitoring and Usage

pmap
cat /proc/meminfo
cat /proc/sys/vm/*
free
vmstat -S m
vmstat -d
vmstat -p /dev/sdb1

OOM Killer​

Ways to deal with memory pressure:

  • Permit memory allocations as long as there's free memory.
  • Use swap space to push some resident memory out of core. We can turn on/off the swap by /sbin/swapo[n/ff] -a
  • In Linux, the system overcommits memory (using COW) for user space processes (kernel space are allocated during request time).

We can change the overcommitting policy by:

# $X can be:
# 0: default, permit for certain cases.
# 1: all.
# 2: disable, memory requests will fail when memory commit reaches the size of swap space + configurable (`/proc/sys/vm/overcommit_ratio`) RAM percentage.
echo "vm.overcommit_memory=X"

When the system reaches memory exhaustion, it invokes the OOM-Killer which decides to kill process by the /proc/[pid]/oom_score. We can modify this value by adjusting /prov/[pid]/oom_adj and /prov/[pid]/oom_adj_score.