Parece que é:
oom_score = badness * 1000 / totalpages
com base no código do kernel link .
static int proc_oom_score(struct seq_file *m, struct pid_namespace *ns,
struct pid *pid, struct task_struct *task)
{
unsigned long totalpages = totalram_pages + total_swap_pages;
unsigned long points = 0;
points = oom_badness(task, NULL, NULL, totalpages) *
1000 / totalpages;
seq_printf(m, "%lu\n", points);
return 0;
}