#define OVERCOMMIT_GUESS        0 // default
#define OVERCOMMIT_ALWAYS       1  // redis
#define OVERCOMMIT_NEVER        2 // postgres

The Linux kernel supports the following overcommit handling modes

0	-	Heuristic overcommit handling. Obvious overcommits of
		address space are refused. Used for a typical system. It
		ensures a seriously wild allocation fails while allowing
		overcommit to reduce swap usage.  root is allowed to 
		allocate slightly more memory in this mode. This is the 
		default.

1	-	Always overcommit. Appropriate for some scientific
		applications. Classic example is code using sparse arrays
		and just relying on the virtual memory consisting almost
		entirely of zero pages.

2	-	Don't overcommit. The total address space commit
		for the system is not permitted to exceed swap + a
		configurable amount (default is 50%) of physical RAM.
		Depending on the amount you use, in most situations
		this means a process will not be killed while accessing
		pages but will receive errors on memory allocation as
		appropriate.

		Useful for applications that want to guarantee their
		memory allocations will be available in the future
		without having to initialize every page.

grep -i commit /proc/meminfo

int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
{
	long free, allowed, reserve;

	VM_WARN_ONCE(percpu_counter_read(&vm_committed_as) <
			-(s64)vm_committed_as_batch * num_online_cpus(),
			"memory commitment underflow");

	vm_acct_memory(pages);

	/*
	 * Sometimes we want to use more memory than we have
	 */
	if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
		return 0;

	if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
		free = global_page_state(NR_FREE_PAGES);
		free += global_page_state(NR_FILE_PAGES);

		/*
		 * shmem pages shouldn't be counted as free in this
		 * case, they can't be purged, only swapped out, and
		 * that won't affect the overall amount of available
		 * memory in the system.
		 */
		free -= global_page_state(NR_SHMEM);

		free += get_nr_swap_pages();

		/*
		 * Any slabs which are created with the
		 * SLAB_RECLAIM_ACCOUNT flag claim to have contents
		 * which are reclaimable, under pressure.  The dentry
		 * cache and most inode caches should fall into this
		 */
		free += global_page_state(NR_SLAB_RECLAIMABLE);

		/*
		 * Leave reserved pages. The pages are not for anonymous pages.
		 */
		if (free <= totalreserve_pages)
			goto error;
		else
			free -= totalreserve_pages;

		/*
		 * Reserve some for root
		 */
		if (!cap_sys_admin)
			free -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);

		if (free > pages)
			return 0;

		goto error;
	}

	allowed = vm_commit_limit();
	/*
	 * Reserve some for root
	 */
	if (!cap_sys_admin)
		allowed -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);

	/*
	 * Don't let a single process grow so big a user can't recover
	 */
	if (mm) {
		reserve = sysctl_user_reserve_kbytes >> (PAGE_SHIFT - 10);
		allowed -= min_t(long, mm->total_vm / 32, reserve);
	}

	if (percpu_counter_read_positive(&vm_committed_as) < allowed)
		return 0;
error:
	vm_unacct_memory(pages);

	return -ENOMEM;
}

#!/bin/bash

while read -r pid comm
do
    printf '%d\t%d\t%s\n' "$pid" "$(cat /proc/$pid/oom_score)" "$comm"
done < <(ps -e -o pid= -o comm=) | sort -k2 -n