Re: [RFC][-mm][PATCH 1/6] oom-killer: updates for classification of OOM

Christoph Lameter
2009-11-02T17:11:34Z

On Mon, 2 Nov 2009, KAMEZAWA Hiroyuki wrote:

> /*
> - * Types of limitations to the nodes from which allocations may occur
> + * Types of limitations to zones from which allocations may occur
> */

"Types of limitations that may cause OOMs"? MEMCG limitations are not zone
based.

> */
>
> -unsigned long badness(struct task_struct *p, unsigned long uptime)
> +static unsigned long __badness(struct task_struct *p,
> + unsigned long uptime, enum oom_constraint constraint,
> + struct mem_cgroup *mem)
> {
> unsigned long points, cpu_time, run_time;
> struct mm_struct *mm;

Why rename this function? You are adding a global_badness anyways.

> + /*
> + * In numa environ, almost all allocation will be against NORMAL zone.

The typical allocations will be against the policy_zone! SGI IA64 (and
others) have policy_zone == GFP_DMA.

> + * But some small area, ex)GFP_DMA for ia64 or GFP_DMA32 for x86-64
> + * can cause OOM. We can use policy_zone for checking lowmem.
> + */

Simply say that we are checking if the zone constraint is below the policy
zone?

> + * Now, only mempolicy specifies nodemask. But if nodemask
> + * covers all nodes, this oom is global oom.
> + */
> + if (nodemask && !nodes_equal(node_states[N_HIGH_MEMORY], *nodemask))
> + ret = CONSTRAINT_MEMORY_POLICY;

Huh? A cpuset can also restrict the nodes?

> + /*
> + * If not __GFP_THISNODE, zonelist containes all nodes. And if

Dont see any __GFP_THISNODE checks here.

> panic("out of memory from page fault. panic_on_oom is selected.\n");
>
> read_lock(&tasklist_lock);
> - __out_of_memory(0, 0); /* unknown gfp_mask and order */
> + /*
> + * Considering nature of pages required for page-fault,this must be
> + * global OOM (if not cpuset...). Then, CONSTRAINT_NONE is correct.
> + * zonelist, nodemasks are unknown...
> + */
> + __out_of_memory(0, CONSTRAINT_NONE, 0, NULL);
> read_unlock(&tasklist_lock);

Page faults can occur on processes that have memory restrictions.