Hi,
I'm curious about what will it happen when alloc_pages_node(memoryless_node).
If the memory is allocated from the most preferable node for the @memoryless_node,
why we need to bother and use cpu_to_mem() in the caller site?
If not, why the memory allocation subsystem refuses to find a preferable node
for @memoryless_node in this case? Does it intend on some purpose or
it can't find in some cases?
Thanks,
Lai
Added CC to Tejun (workqueue maintainer).
On 07/18/2014 07:09 AM, Nishanth Aravamudan wrote:
> In the presence of memoryless nodes, the workqueue code incorrectly uses
> cpu_to_node() to determine what node to prefer memory allocations come
> from. cpu_to_mem() should be used instead, which will use the nearest
> NUMA node with memory.
>
> Signed-off-by: Nishanth Aravamudan <nacc@xxxxxxxxxxxxxxxxxx>
>
> diff --git a/kernel/workqueue.c b/kernel/workqueue.c
> index 35974ac..0bba022 100644
> --- a/kernel/workqueue.c
> +++ b/kernel/workqueue.c
> @@ -3547,7 +3547,12 @@ static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs)
> for_each_node(node) {
> if (cpumask_subset(pool->attrs->cpumask,
> wq_numa_possible_cpumask[node])) {
> - pool->node = node;
> + /*
> + * We could use local_memory_node(node) here,
> + * but it is expensive and the following caches
> + * the same value.
> + */
> + pool->node = cpu_to_mem(cpumask_first(pool->attrs->cpumask));
> break;
> }
> }
> @@ -4921,7 +4926,7 @@ static int __init init_workqueues(void)
> pool->cpu = cpu;
> cpumask_copy(pool->attrs->cpumask, cpumask_of(cpu));
> pool->attrs->nice = std_nice[i++];
> - pool->node = cpu_to_node(cpu);
> + pool->node = cpu_to_mem(cpu);
>
> /* alloc pool ID */
> mutex_lock(&wq_pool_mutex);
>
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