A couple of comments ...
It took me an extra couple of passes to understand this code.
I wonder if the following, essentially equivalent (if I didn't
break something - never tested this) is easier to understand:
#ifdef CONFIG_NUMA
/*
* In the NUMA case we may have gotten here because the
* memory policies or cpusets have restricted the allocation.
*/
{
nodemask_t nodes; /* compute nodes not allowd */
nodes = node_online_map;
for (z = zonelist->zones; *z; z++)
if (cpuset_zone_allowed(*z, gfp_mask))
node_clear((*z)->zone_pgdat->node_id,
nodes);
/*
* If there are any nodes left set in 'nodes', these
* are nodes the cpuset or mempolicy settings aren't
* letting us use. In that case, return NULL to the
* current task, rather than invoking out_of_memory()
* on the system.
*/
if (!nodes_empty(nodes))
return NULL;
}
#endif
Second point - I thought I had already throttled the oom_killer
to some degree, with the lines, in mm/oom_kill.c select_bad_process():
/* If p's nodes don't overlap ours, it won't help to kill p. */
if (!cpuset_excl_nodes_overlap(p))
continue;
What your patch is doing affectively disables the oom_killer for
big numa systems, rather than having it operate within the set
of tasks using overlapping resources.
Do we need this more radical constraint on the oom_killer?
--
I won't rest till it's the best ...
Programmer, Linux Scalability
Paul Jackson <[email protected]> 1.925.600.0401
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