On Wed, 29 Jan 2014, Christoph Lameter wrote:
> > > 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();
> >
> > I'm wondering why return NUMA_NO_NODE wouldn't have the same effect and
> > prefer the local node?
> >
>
> The idea here seems to be that the allocation may occur from a cpu that is
> different from where the process will run later on.
>
Yeah, that makes sense for kthreadd, but I'm wondering why we have to
return numa_mem_id() rather than just NUMA_NO_NODE. Sorry for not being
specific about doing s/numa_mem_id/NUMA_NO_NODE/ here.
That should just turn kmem_cache_alloc_node() into kmem_cache_alloc() and
alloc_pages_node() into alloc_pages() for the allocators that use this
return value, task_struct and thread_info. If that's not allocating local
memory, if possible, and numa_mem_id() magically does, then there's a
problem.
Eric, did you try this when writing 207205a2ba26 ("kthread: NUMA aware
kthread_create_on_node()") or was it always numa_node_id() from the
beginning?
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