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Subject[PATCH] kthread: ensure locality of task_struct allocations
In the presence of memoryless nodes, numa_node_id()/cpu_to_node() will
return the current CPU's NUMA node, but that may not be where we expect
to allocate from memory from. Instead, we should use
numa_mem_id()/cpu_to_mem(). On one ppc64 system with a memoryless Node
0, this ends up saving nearly 500M of slab due to less fragmentation.

Signed-off-by: Nishanth Aravamudan <nacc@linux.vnet.ibm.com>

diff --git a/kernel/kthread.c b/kernel/kthread.c
index b5ae3ee..8573e4e 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -217,7 +217,7 @@ int tsk_fork_get_node(struct task_struct *tsk)
if (tsk == kthreadd_task)
return tsk->pref_node_fork;
#endif
- return numa_node_id();
+ return numa_mem_id();
}

static void create_kthread(struct kthread_create_info *create)
@@ -369,7 +369,7 @@ struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
{
struct task_struct *p;

- p = kthread_create_on_node(threadfn, data, cpu_to_node(cpu), namefmt,
+ p = kthread_create_on_node(threadfn, data, cpu_to_mem(cpu), namefmt,
cpu);
if (IS_ERR(p))
return p;


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